
Elementi di Analisi Complessa.
Funzioni di una variabile (2a edizione)
Carlo Presilla
Springer, collana UNITEXT (2014)
Show Abstract
Questo testo, giunto alla seconda edizione, è adatto per
una prima esposizione della teoria delle funzioni di singola
variabile complessa e si rivolge a studenti di Fisica, Matematica
e Ingegneria che abbiano acquisito le nozioni fondamentali
dell'Analisi Matematica reale. L esigenza di una nuova pubblicazione
nasce dall idea di effettuare una selezione di argomenti, ritenuti
fondamentali, la cui esposizione risulti sistematica e
autoconsistente in circa 60 ore di lezione mantenendo, al tempo
stesso, il rigore matematico volto a favorire la maturazione
scientifica dello studente e prepararlo alla lettura di testi
avanzati. A corredo della trattazione teorica vengono proposti
circa 250 esercizi, raccolti tra le prove scritte assegnate per
il superamento del corso, tutti forniti di soluzione dettagliata.
Il loro svolgimento costituisce una parte imprescindibile per
l'acquisizione della materia.


Elementi di Analisi Complessa.
Funzioni di una variabile
Carlo Presilla
Springer, collana UNITEXT (2011)
Show Abstract
Questo testo è adatto per una prima esposizione della
teoria delle funzioni di singola variabile complessa. Esso
si rivolge a studenti di Fisica, Matematica e Ingegneria che
abbiano acquisito le nozioni fondamentali dell'Analisi
Matematica reale. L'esigenza di una nuova pubblicazione
nasce dall'idea di effettuare una selezione di argomenti,
ritenuti fondamentali, la cui esposizione risulti
sistematica e autoconsistente in circa 60 ore di lezione
mantenendo, al tempo stesso, il rigore matematico volto a
favorire la maturazione scientifica dello studente e
prepararlo alla lettura di testi avanzati. A corredo della
trattazione teorica, vengono proposti oltre 200 esercizi
tutti forniti di soluzione dettagliata. Il loro svolgimento
costituisce una parte imprescindibile per l'acquisizione
della materia.

74 
Spinhelix states in the XXZ
spin chain with strong boundary dissipation
Vladislav Popkov, Johannes Schmidt, Carlo Presilla
J. Phys. A: Math. Theor. 50 435302 (2017)
Show Abstract
We investigate the nonequilibrium steady state (NESS) in
an open quantum XXZ chain attached at the ends to polarization
baths with unequal polarizations. Using the general theory
developed in Popkov (2017 Phys. Rev. A 95 052131), we show
that in the critical XXZ Δ<1 easy plane case, the
steady current in large systems under strong driving shows
resonancelike behaviour, by an infinitesimal change of the
spin chain anisotropy or other parameters. Alternatively, by
fine tuning the system parameters and varying the boundary
dissipation strength, we observe a change of the NESS current
from diffusive (of order 1/N, for small dissipation strength)
to ballistic regime (of order 1, for large dissipation
strength). This drastic change results from an accompanying
structural change of the NESS, which becomes a pure spinhelix
state characterized by a winding number which is
proportional to the system size. We calculate the critical
dissipation strength needed to observe this surprising effect.

73 
Thermalization of
noninteracting quantum systems coupled to blackbody radiation:
A Lindbladbased analysis
Massimo Ostilli, Carlo Presilla
Phys. Rev. A 95 062112 (2017)
Show Abstract
We study the thermalization of an ensemble of N
elementary, arbitrarilycomplex, quantum sys tems, mutually
noninteracting but coupled as electric or magnetic dipoles to
a blackbody radiation. The elementary systems can be all the
same or belonging to different species, distinguishable or
indistinguishable, located at fixed positions or having
translational degrees of freedom. Even if the energy spectra
of the constituent systems are nondegenerate, as we suppose,
the ensemble unavoid ably presents degeneracies of the energy
levels and/or of the energy gaps. We show that, due to these
degeneracies, a thermalization analysis performed by the
popular quantum optical master equation reveals a number of
serious pathologies, possibly including a lack of
ergodicity. On the other hand, a consistent thermalization
scenario is obtained by introducing a Lindbladbased approach,
in which the Lindblad operators, instead of being derived from
a microscopic calculation, are established as the elements of
an operatorial basis with squared amplitudes fixed by imposing
a detailed balance condition and requiring their
correspondence with the dipole transition rates evaluated at
the first order perturbation theory. Due to the above
mentioned degeneracies, this procedure suffers a basis
arbitrariness which, however, can be removed exploiting the
fact that the themalization of an en semble of equal
noninteracting systems cannot rely on the ensemble size. As a
result, we provide a clearcut partitioning of the
thermalization time into dissipation and decoherence times,
for which we derive formulas giving the dependence on the
energy levels of the elementary systems, the size N of the
ensemble and the temperature of the blackbody radiation.

72 
Targeting pure quantum states
by strong noncommutative dissipation
Vladislav Popkov, Carlo Presilla, Johannes Schmidt
Phys. Rev. A 95 052131 (2017)
Show Abstract
We propose a solution to the problem of realizing a
predefined and arbitrary pure quantum state, based on the
simultaneous presence of coherent and dissipative dynamics,
noncommuting on the target state and in the limit of strong
dissipation. More precisely, we obtain a necessary and
sufficient criterion whereby the nonequilibrium steady state
(NESS) of an open quantum system described by a Lindblad
master equation approaches a target pure state in the Zeno
regime, i.e., for infinitely large dissipative coupling. We
also provide an explicit formula for the characteristic
dissipative strength beyond which the purity of the NESS
becomes effective, thus paving the way to an experimental
implementation of our criterion. For an illustration, we deal
with targeting a Bell state, an arbitrary pure state of N
qubits, and a spinhelix state of N qubits.

71 
Thermalization of the
LipkinMeshkovGlick model in blackbody radiation
Tommaso Macrì, Massimo Ostilli, Carlo Presilla
Phys. Rev. A 95 042107 (2017)
Show Abstract
In a recent work, we have derived simple Lindbladbased
equations for the thermalization of systems in contact with a
thermal reservoir. Here, we apply these equations to the
LipkinMeshkovGlick model in contact with blackbody radiation
and analyze the dipole matrix elements involved in the
thermalization process. We find that the thermalization can be
complete only if the density is sufficiently high, while, in
the limit of low density, the system thermalizes partially,
namely, within the Hilbert subspaces where the total spin has
a fixed value. In this regime, and in the isotropic case, we
evaluate the characteristic thermalization time analytically,
and show that it diverges with the system size in
correspondence with the critical points and inside the
ferromagnetic region. Quite interestingly, at zero temperature
the thermalization time diverges only quadratically with the
system size, whereas quantum adiabatic algorithms, aimed at
finding the ground state of the same system, imply a cubic
divergence of the required adiabatic time.

70 
Fermi's golden rule for Nbody
systems in a blackbody radiation
Massimo Ostilli, Carlo Presilla
Phys. Rev. A 94 032514 (2016)
Show Abstract
We review the calculation of Fermi's golden rule for a system of
Nbody dipoles, magnetic or electric, weakly interacting with a
blackbody radiation. By using the magnetic or electric fieldfield
correlation function evaluated in the 1960s for the blackbody
radiation, we deduce a general formula for the transition rates and
study its limiting, fully coherent or fully incoherent, regimes.

69 
Asymptotic lower bound for the gap
of Hermitian matrices having ergodic ground states and infinitesimal
offdiagonal elements
Massimo Ostilli, Carlo Presilla
Europhys. Lett. 113 40002 (2016)
Show Abstract

68 
Obtaining pure steady states in
nonequilibrium quantum systems with strong dissipative couplings
Vladislav Popkov, Carlo Presilla
Phys. Rev. A 93 022111 (2016)
Show Abstract
Dissipative preparation of a pure steady state usually involves a
commutative action of a coherent and a dissipative dynamics on the
target state. Namely, the target pure state is an eigenstate of both
the coherent and dissipative parts of the dynamics. We show that
working in the Zeno regime, i.e., for infinitely large dissipative
coupling, one can generate a pure state by a noncommutative action, in
the above sense, of the coherent and dissipative dynamics. A
corresponding Zeno regime pureness criterion is derived. We illustrate
the approach, looking at both its theoretical and applicative aspects,
in the example case of an open XXZ spin1/2 chain, driven out of
equilibrium by boundary reservoirs targeting different spin
orientations. Using our criterion, we find two families of pure
nonequilibrium steady states, in the Zeno regime, and calculate the
dissipative strengths effectively needed to generate steady states
which are almost indistinguishable from the target pure states.

67 
Binary mixtures of chiral gases
Carlo Presilla, Giovanni JonaLasinio
PIERS Proceedings, 835839, July 69, Prague, 2015
Show Abstract
A possible solution of the well known paradox of chiral
molecules is based on the idea of spontaneous symmetry
breaking. At low pressure the molecules are delocalized
between the two minima of a given molecular potential while
at higher pressure they become localized in one minimum due
to the intermolecular dipoledipole interactions. Evidence
for such a phase transition is provided by measurements of
the inversion spectrum of ammonia and deuterated ammonia at
different pressures. In particular, at pressure greater than
a critical value no inversion line is observed. These data
are well accounted for by a model previously developed and
recently extended to mixtures. In the present paper, we
discuss the variation of the critical pressure in binary
mixtures as a function of the fractions of the constituents.

66 
Spontaneous symmetry breaking and
inversionline spectroscopy in gas mixtures
Carlo Presilla, Giovanni JonaLasinio
Phys. Rev. A 91 022706 (2015)
Show Abstract
According to quantum mechanics chiral molecules, that is
molecules that rotate the polarization of light, should not exist.
The simplest molecules which can be chiral have four or more atoms
with two arrangements of minimal potential energy that are
equivalent up to a parity operation. Chiral molecules correspond to
states localized in one potential energy minimum and can not be
stationary states of the Schrödinger equation. A possible
solution of the paradox can be founded on the idea of spontaneous
symmetry breaking. This idea was behind work we did previously
involving a localization phase transition: at low pressure the
molecules are delocalized between the two minima of the potential
energy while at higher pressure they become localized in one minimum
due to the intermolecular dipoledipole interactions. Evidence for
such a transition is provided by measurements of the inversion
spectrum of ammonia and deuterated ammonia at different pressures.
A previously proposed model gives a satisfactory account of the
empirical results without free parameters. In this paper, we extend
this model to gas mixtures. We find that also in these systems a
phase transition takes place at a critical pressure which depends on
the composition of the mixture. Moreover, we derive formulas giving
the dependence of the inversion frequencies on the pressure. These
predictions are susceptible to experimental test.

65 
A perturbative probabilistic approach
to quantum manybody systems
Andrea Di Stefano , Massimo Ostilli, Carlo Presilla
J. Stat. Mech. P04002 (2013)
Show Abstract
In the probabilistic approach to quantum manybody systems, the
groundstate energy is the solution of a nonlinear scalar equation
written either as a cumulant expansion or as an expectation with
respect to a probability distribution of the potential and hopping
(amplitude and phase) values recorded during an infinitely lengthy
evolution. We introduce a perturbative expansion of this
probability distribution which conserves, at any order, a
multinomiallike structure, typical of uncorrelated systems, but
includes, order by order, the statistical correlations provided by
the cumulant expansion. The proposed perturbative scheme is
successfully tested in the case of pseudospin 1/2 hardcore boson
Hubbard models also when affected by a phase problem due to
an applied magnetic field.

64 
Phase transition and annealing
in quantum random energy models
Carlo Presilla, Massimo Ostilli
arXiv:1002.4409 (2010)
Show Abstract
By using a previously established exact characterization of
the ground state of random potential systems in the
thermodynamic limit, we determine the ground and first
excited energy levels of quantum random energy models,
discrete and continuous, and rigorously establish the
existence of a first order quantum phase transition. Our
analysis, corroborated by Monte Carlo simulations, suggests
that the presence of an exponentially vanishing minimal gap
at the transition does not prevent the success of a quantum
annealing algorithm.

63 
Thermodynamical approaches to
efficient sympathetic cooling in ultracold FermiBose atomic
mixtures Michael BrownHayes, Qun Wei, Carlo
Presilla, Roberto Onofrio
Phys. Rev. A 78, 013617 (2008)
Show Abstract
We discuss the cooling efficiency of ultracold FermiBose
mixtures in speciesselective traps using a thermodynamical
approach. The dynamics of evaporative cooling trajectories
is analyzed in the specific case of bichromatic optical
dipole traps also taking into account the effect of partial
spatial overlap between the Fermi gas and the thermal
component of the Bose gas. We show that large trapping
frequency ratios between the Fermi and the Bose species
allow for the achievement of a deeper Fermi degeneracy,
consolidating in a thermodynamic setting earlier arguments
based on more restrictive assumptions. In particular, we
confirm that the minimum temperature of the mixture is
obtained at the crossover between boson and fermion heat
capacities, and that below such a temperature sympathetic
cooling vanishes. When the effect of partial overlap is
taken into account, optimal sympathetic cooling of the Fermi
species may be achieved by properly tuning the relative
trapping strength of the two species in a timedependent
fashion. Alternatively, the dimensionality of the trap in
the final stage of cooling can be changed by increasing the
confinement strength, which also results in a crossover of
the heat capacities at deeper Fermi degeneracies. This
technique may be extended to FermiBose degenerate mixtures
in optical lattices.

62 
The
exact ground state for a class of matrix Hamiltonian models:
quantum phase transition and universality in the
thermodynamic limit Massimo Ostilli, Carlo
Presilla
J. Stat. Mech. P11012 (2006)
Show Abstract
By using a recently proposed probabilistic approach, we
determine the exact ground state of a class of matrix
Hamiltonian models characterized by the fact that in the
thermodynamic limit the multiplicities of the potential
values assumed by the system during its evolution are
distributed according to a multinomial probability
density. The class includes (i) the uniformly fully
connected models, namely a collection of states all
connected with equal hopping coefficients and in the
presence of a potential operator with arbitrary levels and
degeneracies, and (ii) the random potential systems, in
which the hopping operator is generic and arbitrary
potential levels are assigned randomly to the states with
arbitrary probabilities. For this class of models we find a
universal thermodynamic limit characterized only by the
levels of the potential, rescaled by the groundstate energy
of the system for zero potential, and by the corresponding
degeneracies (probabilities). If the degeneracy
(probability) of the lowest potential level tends to zero,
the ground state of the system undergoes a quantum phase
transition between a normal phase and a frozen phase with
zero hopping energy. In the frozen phase the ground state
condenses into the subspace spanned by the states of the
system associated with the lowest potential level.

61 
On the statistics of quantum expectations for systems in
thermal equilibrium Giovanni JonaLasinio, Carlo
Presilla
QUANTUM MECHANICS: Are There Quantum Jumps?  and On the
Present Status of Quantum Mechanics, AIP Conference
Proceedings  June 27, 2006  Vol. 844, p. 200205, edited
by A. Bassi, D. Dürr, T. Weber, N. Zanghi
Show Abstract
The recent remarkable developments in quantum optics,
mesoscopic and cold atom physics have given reality to wave
functions. It is then interesting to explore the
consequences of assuming ensembles over the wave functions
simply related to the canonical density matrix. In this note
we analyze a previously introduced distribution over wave
functions which naturally arises considering the
Schrödinger equation as an infinite dimensional
dynamical system. In particular, we discuss the low
temperature fluctuations of the quantum expectations of
coordinates and momenta for a particle in a double well
potential. Our results may be of interest in the study of
chiral molecules.

60 
Ground state of manybody lattice systems via a central
limit theorem Carlo Presilla, Massimo Ostilli
Int. J. Mod. Phys. B 20, 27702778 (2006)
Show Abstract
We review a novel approach to evaluate the groundstate
properties of manybody lattice systems based on an exact
probabilistic representation of the dynamics and its long
time approximation via a central limit theorem. The choice
of the asymptotic density probability used in the
calculation is discussed in detail.

59 
An
analytical probabilistic approach to the ground state of
lattice quantum systems: exact results in terms of a cumulant
expansion
Massimo Ostilli, Carlo Presilla
J. Stat. Mech. P04007 (2005)
Show Abstract
We present a large deviation analysis of a recently proposed
probabilistic approach to the study of the groundstate
properties of lattice quantum systems. The groundstate
energy as well as the correlation functions in the ground
state are exactly determined as series expansions in the
cumulants of the multiplicities of the potential and hopping
energies assumed by the system during its longtime
evolution. Once these cumulants are known, even at a finite
order, our approach provides the ground state analytically
as a function of the Hamiltonian parameters. A scenario of
possible applications of the analytic character of the
present approach is discussed.

58 
Exact Monte Carlo time dynamics in manybody lattice quantum
systems Massimo Ostilli, Carlo Presilla
J. Phys. A 38, 405426 (2005)
Show Abstract
On the basis of a FeynmanKactype formula involving Poisson
stochastic processes, a Monte Carlo algorithm has recently
been introduced, which describes exactly the real or
imaginarytime evolution of manybody lattice quantum
systems. We extend this algorithm to the exact simulation of
timedependent correlation functions. The techniques
generally employed in Monte Carlo simulations to control
fluctuations, namely reconfigurations and importance
sampling, are adapted to the present algorithm and their
validity is rigorously proved. We complete the analysis by
several examples for the hardcore boson Hubbard model and
for the Heisenberg model.

57 
Signatures of macroscopic quantum coherence in ultracold
dilute Fermi gases Roberto Onofrio, Carlo Presilla
Phys. Rev. A 70, 043608 (2004)
Show Abstract
We propose a doublewell configuration for optical trapping
of ultracold twospecies FermiBose atomic mixtures. Two
signatures of macroscopic quantum coherence attributable to
a superfluid phase transition for the Fermi gas are
analyzed. The first signature is based upon tunneling of
Fermi pairs when the power of the deconfining laser beam is
significantly reduced. The second relies on the observation
of interference fringes in a regime where the fermions are
trapped in two sharply separated minima of the
potential. Both signatures rely on small decoherence times
for the Fermi samples, which should be possible by reaching
low temperatures using a Bose gas as a refrigerator, and a
bichromatic optical dipole trap for confinement, with
optimal heatcapacity matching between the two species.

56 
Ground state of manybody lattice systems: an analytical
probabilistic approach Massimo Ostilli, Carlo
Presilla
New
J. Phys. 6, 107 (2004)
Show Abstract
On the grounds of a FeynmanKactype formula for Hamiltonian
lattice systems, we derive analytical expressions for the
matrix elements of the evolution operator. These expressions
are valid at long times when a central limit theorem
applies. As a remarkable result, we find that the
groundstate energy as well as all the correlation functions
in the ground state are determined semianalytically by
solving a simple scalar equation. Furthermore, explicit
solutions of this equation are obtained in the
noninteracting case.

55 
Classical versus quantum structures: the case of pyramidal
molecules Carlo Presilla, Giovanni JonaLasinio,
Cristina Toninelli
Multiscale Methods in Quantum Mechanics: Theory and
Experiment, edited by P. Blanchard, G. Dell'Antonio
(Birkhäuser, Boston, 2004), p. 119127
Show Abstract
In a previous paper we proposed a model to describe a gas of
pyramidal molecules interacting via dipoledipole
interactions. The interaction modifies the tunneling
properties between the classical equilibrium configurations
of the single molecule and, for sufficiently high pressure,
the molecules become localized in these classical
configurations. The model explains quantitatively the shift
to zerofrequency of the inversion line observed upon
increase of the pressure in a gas of ammonia or deuterated
ammonia. Here we analyze further the model especially with
respect to stability questions.

54 
Ultracold atomic FermiBose mixtures in bichromatic optical
dipole traps: a novel route to study fermion
superfluidity Roberto Onofrio, Carlo Presilla
J. Stat. Phys. 115, 5789 (2004)
Show Abstract
The study of low density, ultracold atomic Fermi gases is a
promising avenue to understand fermion superfluidity from
first principles. One technique currently used to bring
Fermi gases in the degenerate regime is sympathetic cooling
through a reservoir made of an ultracold Bose gas. We
discuss a proposal for trapping and cooling of twospecies
FermiBose mixtures into optical dipole traps made from
combinations of laser beams having two different
wavelengths. In these bichromatic traps it is possible, by a
proper choice of the relative laser powers, to selectively
trap the two species in such a way that fermions experience
a stronger confinement than bosons. As a consequence, a deep
Fermi degeneracy can be reached having at the same time a
softer degenerate regime for the Bose gas. This leads to an
increase in the sympathetic cooling efficiency and allows
for higher precision thermometry of the FermiBose mixture.

53 
Cooling dynamics of ultracold twospecies FermiBose
mixtures Carlo Presilla, Roberto Onofrio
Phys. Rev. Lett. 90, 030404 (2003)
Show Abstract
We compare strategies for evaporative and sympathetic
cooling of twospecies FermiBose mixtures in singlecolor
and twocolor optical dipole traps. We show that in the
latter case a large heat capacity of the bosonic species can
be maintained during the entire cooling process. This could
allow one to efficiently achieve a deep Fermi degeneracy
regime having at the same time a significant thermal
fraction for the Bose gas, crucial for a precise thermometry
of the mixture. Two possible signatures of a superfluid
phase transition for the Fermi species are discussed.

52 
Reaching Fermi degeneracy in twospecies optical dipole
traps Roberto Onofrio, Carlo Presilla
Phys. Rev. Lett. 89, 100401 (2002)
Show Abstract
We propose the use of a combined optical dipole trap to
achieve Fermi degeneracy by sympathetic cooling with a
different bosonic species. Two fardetuned pairs of laser
beams focused on the atomic clouds are used to confine the
two atomic species with different trapping strengths. We
show that a deep Fermi degeneracy regime can be potentially
achieved earlier than BoseEinstein condensation, as
discussed in the favorable situation of a 6Li23Na
mixture. This opens up the possibility of experimentally
investigating a mixture of superfluid Fermi and normal Bose
gases.

51 
Quantum breaking time near classical equilibrium points
Fabrizio Cametti, Carlo Presilla
Phys. Rev. Lett. 89, 040403 (2002)
Show Abstract
In the evolution of distributions localized around classical
equilibrium points, the quantumclassical correspondence
breaks down at a time, the socalled quantum breaking, or
Ehrenfest time, which is related to the minimal separation
of the quantum levels in proximity of the classical
equilibrium energy. By studying onedimensional systems with
single and doublewell polynomial potentials, we find that
the Ehrenfest time diverges logarithmically with the inverse
of the Planck constant whenever the equilibrium point is
exponentially unstable. In all the other cases, we have a
power law divergence with the exponent determined by the
degree of the potential near the equilibrium point.

50 
Interaction induced localization in a gas of pyramidal
molecules Giovanni JonaLasinio, Carlo Presilla,
Cristina Toninelli
Phys. Rev. Lett. 88, 123001 (2002)
Show Abstract
We propose a model to describe a gas of pyramidal molecules
interacting via dipoledipole interactions. The interaction
modifies the tunneling properties between the classical
equilibrium configurations of the single molecule and, for
sufficiently high pressure, the molecules become localized
in these classical configurations. We explain
quantitatively, without free parameters, the shift to zero
frequency of the inversion line observed upon increase of
the pressure in a gas of ammonia or deuterated ammonia. For
sufficiently high pressures, our model suggests the
existence of a superselection rule for states of different
chirality in substituted derivatives.

49 
Stationary states of BoseEinstein condensates in single
and multiwell trapping potentials Roberto
D'Agosta, Boris A. Malomed, Carlo Presilla
Laser Physics 12, 3742 (2002)
Show Abstract
The stationary solutions of the GrossPitaevskii equation
can be divided in two classes: those which reduce, in the
limit of vanishing nonlinearity, to the eigenfunctions of
the associated Schrödinger equation and those which do
not have linear counterpart. Analytical and numerical
results support an existence condition for the solutions of
the first class in terms of the ratio between their proper
frequency and the corresponding linear eigenvalue. For
onedimensional confined systems, we show that solutions
without linear counterpart do exist in presence of a
multiwell external potential. These solutions, which in the
limit of strong nonlinearity have the form of chains of dark
or bright solitons located near the extrema of the
potential, represent macroscopically excited states of a
BoseEinstein condensate and are in principle experimentally
observable.

48 
Environment induced localization and superselection rules in
a gas of pyramidal molecules Giovanni JonaLasinio,
Carlo Presilla, Cristina Toninelli
Mathematical Physics in Mathematics and Physics. Quantum
and Operator Algebraic aspects, edited by R. Longo,
Fields Institute Communications, Vol. 30, 2001,
p. 207217
Show Abstract
We propose a model to describe a gas of pyramidal molecules
interacting via dipoledipole interactions. A cooperative
effect induced by the interaction modifies the tunneling
properties between the classical equilibrium configurations
of the single molecule. The model suggests that, for
sufficiently high gas density, the molecules become
localized in these classical configurations. On this basis
it is possible to explain the shift and the disappearance
of the inversion line observed upon increase of the pressure
in a gas of ammonia or deuterated ammonia. The same
mechanism also accounts for the presence of stable optical
activity of certain pyramidal molecules. We discuss the
concept of environment induced superselection rule which has
been invoked in connection with this problem.

47 
States without a linear counterpart in BoseEinstein
condensates Roberto D'Agosta, Carlo Presilla
Phys. Rev. A 65, 043609 (2002)
Show Abstract
We show the existence of stationary solutions of a
onedimensional GrossPitaevskii equation in the presence of
a multiwell external potential that do not reduce to any of
the eigenfunctions of the associated Schrödinger
problem. These solutions, which in the limit of strong
nonlinearity have the form of chains of dark or bright
solitons located near the extrema of the potential,
represent macroscopically excited states of a BoseEinstein
condensate and are in principle experimentally observable.

46 
Evolution of fermionic systems as an expectation over Poisson
processes Matteo Beccaria, Carlo Presilla, Gian
Fabrizio De Angelis, Giovanni JonaLasinio
Int. J. Mod. Phys. B 15, 17401743 (2001)
Show Abstract
We derive an exact probabilistic representation for the
evolution of a Hubbard model with site and spindependent
hopping coefficients and sitedependent interactions in
terms of an associated stochastic dynamics of a collection
of Poisson processes.

45 
Stationary solutions of the GrossPitaevskii equation with
linear counterpart Roberto D'Agosta, Boris
A. Malomed, Carlo Presilla
Phys. Lett. A 275, 424434 (2000)
Show Abstract
We study the stationary solutions of the
Gross–Pitaevskii equation that reduce, in the limit
of vanishing nonlinearity, to the eigenfunctions of the
associated Schrödinger equation. By providing
analytical and numerical support, we conjecture an existence
condition for these solutions in terms of the ratio between
their proper frequency (chemical potential) and the
corresponding linear eigenvalue. We also give approximate
expressions for the stationary solutions which become exact
in the opposite limit of strong nonlinearity. For
onedimensional systems these solutions have the form of a
chain of dark or bright solitons depending on the sign of
the nonlinearity. We demonstrate that in the case of
negative nonlinearity (attractive interaction) the norm of
the solutions is always bounded for dimensions greater than
one.

44 
Probabilistic representation of fermionic lattice systems
Matteo Beccaria, Carlo Presilla, Gian Fabrizio De
Angelis, Giovanni JonaLasinio
Nucl. Phys. B  Proceed. Suppl. 8384, 911913
(2000)
Show Abstract
We describe an exact FeynmanKac type formula to represent
the dynamics of fermionic lattice systems. In this approach
the real time or Euclidean time dynamics is expressed in
terms of the stochastic evolution of a collection of Poisson
processes. From this formula we derive a family of
algorithms for Monte Carlo simulations, parametrized by the
jump rates of the Poisson processes.

43 
Comparison between quantum and classical dynamics in the
effective action formalism Fabrizio Cametti,
Giovanni JonaLasinio, Carlo Presilla, Fabio Toninelli
New directions in quantum chaos, Volume 143
International School of Physics Enrico Fermi, edited by
G. Casati, I. Guarneri, U. Smilansky (IOS Press, Amsterdam,
2000), p. 431448
Show Abstract
The present contribution describes the beginning of a
systematic study of semiclassical evolutions using the
effective action formalism. In the first part, after
introducing the formalism of the effective action and its
expansion in powers of h (loopexpansion) in the context of
quantum mechanics, we concentrate on the structure of the
first order corrections in h. These corrections are
evaluated to the second order in the derivative expansion by
two different methods. The first is based on a Euclidean
approach, the second one on an adiabatic approximation in
evaluating functional determinants. In the second part of
the article we put the formalism at work, choosing as our
case study a twodimensional (2D) anharmonic oscillator of
the kind considered in molecular physics. The results of the
simulations show that by increasing h the effective dynamics
tends to regularize the classical motion and becomes
qualitatively very similar to the quantum evolution provided
the energy is sufficiently small.

42 
An
exact representation of the fermion dynamics in terms of
Poisson processes and its connection with Monte Carlo
algorithms Matteo Beccaria, Carlo Presilla, Gian
Fabrizio De Angelis, Giovanni JonaLasinio
Europhys. Lett. 48, 243249 (1999)
Show Abstract
We present a simple derivation of a FeynmanKactype formula
to study fermionic systems. In this approach the real time
or the imaginary time dynamics is expressed in terms of the
evolution of a collection of Poisson processes. This formula
leads to a family of algorithms parametrized by the values
of the jump rates of the Poisson processes. From these an
optimal algorithm can be chosen which coincides with the
Green Function Monte Carlo method in the limit when the
latter becomes exact.

41 
Classical behavior of a macroscopic Schrödinger cat
Carlo Presilla
Quantum Communication, Computing and Measurement 2,
edited by P. Kumar, G. M. D'Ariano, O. Hirota (Kluwer
Academic/Plenum Publishers, New York, 2000), p. 359364
Show Abstract
We study the dynamics of classical and quantum systems
linearly interacting with a classical environment
represented by an infinite set of harmonic oscillators. The
environment induces a dynamical localization of the quantum
state into a generalized coherent state for which the h
→ 0 limit always exists and reproduces the classical
motion. We describe the consequences of this localization on
the behavior of a macroscopic system by considering the
example of a Schröodinger cat.

40 
Continuous measurements in quantum systems Carlo
Presilla, Ubaldo Tambini
Hyp. Int. 114, 123126 (1998)
Show Abstract
During a continuous measurement, quantum systems can be
described by a stochastic Schrödinger equation which,
in the appropriate limit, reproduces the von Neumann
wavefunction collapse. The average behavior on the ensemble
of all measurement results is described by a master equation
obtained from a general model of measurement apparatus
consisting of an infinite set of degrees of freedom linearly
interacting with the measured system and in contact with a
reservoir at high temperature.

39 
Classical and quantum measurements of position
Carlo Presilla, Roberto Onofrio, Marco Patriarca
J. Phys. A: Math. Gen. 30, 73857411 (1997)
Show Abstract
We study the dynamics of classical and quantum systems
undergoing a continuous measurement of position by
schematizing the measurement apparatus with an infinite set
of harmonic oscillators at finite temperature linearly
coupled to the measured system. Selective and nonselective
measurement processes are then introduced according to a
selection of or an average over all possible initial
configurations of the measurement apparatus. At quantum
level, the selective processes are described by a nonlinear
stochastic Schrödinger equation whose solutions evolve
into properly defined coherent states in the case of linear
systems. For arbitrary measured systems, classical behaviour
is always recovered in the macroscopic limit.

38 
Nonlinear resonant tunneling in systems coupled to quantum
reservoirs Carlo Presilla, Johannes Sjöstrand
Phys. Rev. B 55, 93109313 (1997)
Show Abstract
An adiabatic approximation in terms of instantaneous
resonances is developed to study the steadystate and
timedependent transport of interacting electrons in biased
resonanttunneling heterostructures. The resulting model
consists of quantum reservoirs coupled to regions where the
system is described by nonlinear ordinary differential
equations and has a general conceptual interest.

37 
Chaotic properties of quantum manybody systems in the
thermodynamic limit Giovanni JonaLasinio, Carlo
Presilla
Phys. Rev. Lett. 77, 43224325 (1996)
Show Abstract
By using numerical simulations, we investigate the dynamics
of a quantum system of interacting bosons. We find an
increase of properly defined mixing properties when the
number of particles increases at constant density or the
interaction strength drives the system away from
integrability. A correspondence with the dynamical
chaoticity of an associated cnumber system is then used to
infer properties of the quantum system in the thermodynamic
limit.

36 
Transport properties in resonant tunneling
heterostructures Carlo Presilla, Johannes
Sjöstrand
J. Math. Phys. 37, 48164844 (1996)
Show Abstract
An adiabatic approximation in terms of instantaneous
resonances to study the steadystate and timedependent
transport properties of interacting electrons in biased
resonant tunneling heterostructures is used. This approach
leads, in a natural way, to a transport model of large
applicability consisting of reservoirs coupled to regions
where the system is described by a nonlinear
Schrödinger equation. From the mathematical point of
view, this work is nonrigorous but may offer some fresh and
interesting problems involving semiclassical approximation,
adiabatic theory, nonlinear Schrödinger equations, and
dynamical systems.

35 
Spectral properties of quantum Nbody systems versus chaotic
properties of their mean field approximations
Patrizia Castiglione, Giovanni JonaLasinio, Carlo Presilla
J. Phys. A: Math. Gen. 29, 61696182 (1996)
Show Abstract
We present numerical evidence that in a system of
interacting bosons there exists a correspondence between the
spectral properties of the exact quantum Hamiltonian and the
dynamical chaos of the associated meanfield evolution. This
correspondence, analogous to the usual quantumclassical
correspondence, is related to the formal parallel between
the second quantization of the mean field, which generates
the exact dynamics of the quantum Nbody system, and the
first quantization of classical canonical coordinates. The
limit of infinite density and the thermodynamic limit are
then briefly discussed.

34 
Measurement quantum mechanics and experiments on quantum Zeno
effect Carlo Presilla, Roberto Onofrio, Ubaldo
Tambini
Ann. Phys. (N.Y.) 248, 95121 (1996)
Show Abstract
Measurement quantum mechanics, the theory of a quantum
system which undergoes a measurement process, is introduced
by a loop of mathematical equivalencies connecting
previously proposed approaches. The unique phenomenological
parameter of the theory is linked to the physical properties
of an informational environment acting as a measurement
apparatus which allows for an objective role of the
observer. Comparison with a recently reported experiment
suggests how to investigate novel interesting regimes for
the quantum Zeno effect.

33 
Ambipolar tunneling in nearsurface quantum wells
Valentina Emiliani, Andrea Frova, Carlo Presilla
Superlattices and Microstructures 20, 16 (1996)
Show Abstract
We study the photoluminescence from a nearsurface quantum
well in the regime of ambipolar tunneling to the surface
states. Under steadystate excitation an electric field
develops selfconsistently due to the condition of equal
tunneling currents for electrons and holes. The field
induces a Stark shift of the photoluminescence signal which
compares well with experimental data from nearsurface
GaAs/AlGaAs single quantum wells.

32 
Transient tunneling currents in nearsurface quantum
wells B. Bonanni, M. Capizzi, R. Dioletta,
V. Emiliani, A. Frova, C. Presilla, M. Colocci, M. Gurioli,
A. Vinattieri, F. Martelli, Y.L. Chang, J.L. Merz,
S.S. Stone
The Physiscs of Semiconductors Proceedings of the 22nd
International Conference, edited by D.J. Lockwood (World
Scientific, Singapore, 1995), p. 10431046
Show Abstract
Continuouswave and timeresolved photoluminescence at low
temperatures is investigated in near surface quantum wells,
where carrier tunneling to surface states reduces the e1hh1
excitonic emission efficiency. Analysis of the timeresolved
spectra points to a behavior for strained InGaAs/GaAs
interfaces different from AlGaAs/GaAs interfaces, in that
tunneling occurs not only from the freecarrier continuum,
but also from the exciton ground state.

31 
Quantum phenomenology using the path integral approach
Tommaso Calarco, Roberto Onofrio, Carlo Presilla,
Lorenza Viola
Quantum Communications and Measurement, edited by
V. P. Belavkin, O. Hirota, R. L. Hudson (Plenum Press, New
York, 1995), p. 171176
Show Abstract
A quantum measurement model based upon restricted
pathintegrals allows us to study measurements of
generalized position in various onedimensional systems of
phenomenological interest. After a general overview of the
method we discuss the cases of a harmonic oscillator, a
bistable potential and two coupled systems, briefly
illustrating their applications.

30 
Selective relaxation method for numerical solution of
Schrödinger problems Carlo Presilla, Ubaldo
Tambini
Phys. Rev. E 52, 44954498 (1995)
Show Abstract
We propose a numerical method for evaluating eigenvalues and
eigenfunctions of Schrödinger operators with general
confining potentials. The method is selective in the sense
that only the eigenvalue closest to a chosen input energy is
found through an absolutely stable relaxation algorithm
which has a rate of convergence that is infinite. In the
case of bistable potentials the method allows one to
evaluate the fundamental energy splitting for a wide range
of tunneling rates.

29 
Dynamics of quantum collapse in energy measurements
Ubaldo Tambini, Carlo Presilla, Roberto Onofrio
Phys. Rev. A 51, 967975 (1995)
Show Abstract
The influence of continuous measurements of energy with
finite accuracy is studied in various quantum systems
through a restriction of the Feynman path integrals around
the measurement result. The method, which is equivalent to
considering an effective Schrödinger equation with a
nonHermitian Hamiltonian, allows one to study the dynamics
of the wavefunction collapse. A numerical algorithm for
solving the effective Schrödinger equation is developed and
checked in the case of a harmonic oscillator. The
situations, of physical interest, of a twolevel system and
of a metastable quantum well are then discussed. In the
first case, the Zeno inhibition observed in quantum optics
experiments is recovered and extended to nonresonant
transitions, and in the second case we propose an
observation of the inhibition of spontaneous decay in
mesoscopic heterostructures. In all the considered examples,
the effect of the continuous measurement of energy is a
freezing of the evolution of the system proportional to the
accuracy of the measurement itself.

28 
Selfconsistent model for ambipolar tunneling in quantumwell
systems Carlo Presilla, Valentina Emiliani, Andrea
Frova
Semicond. Sci. Technol. 10, 577585 (1995)
Show Abstract
We present a selfconsistent approach to describe ambipolar
tunnelling in asymmetrical double quantum wells under
steadystate excitation and extend the results to the case
of tunnelling from a nearsurface quantum well to surface
states. The results of the model compare very well with the
behaviour observed in photoluminescence experiments in
InGaAs/InP asymmetric double quantum wells and in
nearsurface AlGaAs/GaAs single quantum wells.

27 
On
Schrödinger equations with concentrated
nonlinearities Giovanni Jona Lasinio, Carlo
Presilla, Johannes Sjöstrand
Ann. Phys. (N.Y.) 240, 121 (1995)
Show Abstract
Schrödinger equations with nonlinearities concentrated
in some regions of space are good models of various physical
situations and have interesting mathematical properties. We
show that in the semiclassical limit it is possible to
separate the relevant degrees of freedom by noting that in
the regions where the nonlinearities are effective all
states are suppressed but the metastable ones
(resonances). In this way the description of the nonlinear
regions is reduced to ordinary differential equations weakly
coupled to standard Schrödinger equations valid in the
linear regions. The idea is illustrated through the study of
a prototype equation recently proposed for resonant
tunneling of electrons through a double barrier
heterostructure and for which nonlinear oscillations have
been numerically predicted.

26 
Chaos
in many body quantum systems Carlo Presilla,
Giovanni Jona Lasinio, Federico Capasso
Chaos in mesoscopic systems, edited by G. Casati and
H.A. Cerdeira (World Scientific, Singapore, 1995), p. 310
Show Abstract
A many body quantum system undergoing a multiple resonant
tunneling in a double barrier heterostructure is studied
within a mean field approximation. The resulting nonlinear
Schrödinger equation shows genuine chaos with a
positive maximum Lyapunov exponent. A simplified model of
the same system suggests that chaos develops only if the
interaction among the particles is nonuniform in space.

25 
Interaction mechanisms of nearsurface quantum wells with
oxidized and Hpassivated AlGaAs surfaces
V. Emiliani, B. Bonanni, C. Presilla, M. Capizzi, A. Frova,
Y.L. Chang, I.H. Tan, J.L. Merz, M. Colocci, M. Gurioli
J. Appl. Phys. 75, 51145122 (1994)
Show Abstract
The tunneling mechanism of electrons and holes to surface
states from nearsurface Al0.3Ga0.7As/GaAs quantum wells has
been investigated by steadystate and timeresolved
photoluminescence spectroscopy, near liquidhelium
temperature, of the excitonic e1hh1 transition in the
well. The ensemble of the data, taken over a wide range of
optical excitation levels, for various values of the
tunnelingbarrier thickness, and before and after
passivation of the surface by hydrogen, allows a description
both of the details of the tunneling mechanism and of the
character and behavior of relevant surface states. The main
results are summarized as follows: (i) steadystate
tunneling is ambipolar, namely, separate for electrons and
holes, rather than excitonic; (ii) Spicer's advanced unified
defect model for an oxidized GaAs surface, antisiteAs
donors as dominating surface traps, provides an appropriate
description of the state distribution at the interface
between AlGaAs and its oxide; (iii) hole accumulation in
surface states, resulting from the nominally different
unipolar tunneling probability for the two carriers (and
increasing with excitation level), generates a dipole
electric field across the tunneling barrier, extending into
the well; (iv) hydrogenation efficiently passivates electron
trapping in surface states, but not hole tunneling and the
consequent generation of a surface field by illumination;
(v) the experimental findings agree with a model for
ambipolar tunneling based on a selfconsistent
quantummechanical approach.

24 
Quantum Zeno effect with the FeynmanMensky pathintegral
approach Roberto Onofrio, Carlo Presilla, Ubaldo
Tambini
Phys. Lett. A 183, 135140 (1993)
Show Abstract
A model for the quantum Zeno effect based upon an effective
Schrödinger equation originated by the pathintegral
approach is developed and applied to a twolevel system
simultaneously stimulated by a resonant perturbation. It is
shown that inhibition of stimulated transitions between the
two levels appears as a consequence of the influence of the
meter whenever measurements of energy, either continuous or
pulsed, are performed at quantum level of sensitivity. The
generality of this approach allows one to qualitatively
understand the inhibition of spontaneous transitions as the
decay of unstable particles, originally presented as a
paradox of the quantum measurement theory.

23 
Optimal monitoring of position in nonlinear quantum
systems Michael B. Mensky, Roberto Onofrio, Carlo
Presilla
Phys. Rev. Lett. 70, 28252828 (1993)
Show Abstract
We discuss a model of repeated measurements of position in a
quantum system which is monitored for a finite amount of
time with a finite instrumental error. In this framework we
recover the optimum monitoring of a harmonic oscillator
proposed in the case of an instantaneous collapse of the
wave function into an infiniteaccuracy measurement
result. We also establish numerically the existence of an
optimal measurement strategy in the case of a nonlinear
system. This optimal strategy is completely defined by the
spectral properties of the nonlinear system.

22 
Quantum limit in resonant vacuum tunneling transducers
Roberto Onofrio, Carlo Presilla
Europhys. Lett. 22, 333339 (1993)
Show Abstract
We propose an electromechanical transducer based on a
resonanttunnelling configuration that, with respect to the
standard tunnelling transducers, allows larger tunnelling
currents while using the same bias voltage. The increased
current leads to a decrease of the shot noise and an
increase of the momentum noise which determine the quantum
limit in the system under monitoring. Experiments with
micromachined test masses at 4.2 K could show dominance of
the momentum noise over the Brownian noise, allowing
observation of quantummechanical noise at the mesoscopic
scale.

21 
Nonlinear voltages in multiplelead coherent conductors
Gordey B. Lesovik, Carlo Presilla
Phys. Rev. B 47, 23982401 (1993)
Show Abstract
We use the generalized Smatrix approach to study
multiplelead coherent conductors in the case of finite
applied voltages. In this framework we discuss the
transverse voltage arising in a fourlead conductor with two
symmetric biased leads.

20 
Electronbarrier interaction in a vaccum tunneling probe
Roberto Onofrio, Carlo Presilla
Phys. Lett. A 166, 2428 (1992)
Show Abstract
A model for dealing with energy and momentum exchanges
between ballistic electrons and the vacuum barrier in a
tunneling probe used as an electromechanical transducer is
studied and its physical significance in devices of size
comparable to the mean free path of the tunneling electrons
is discussed.

19 
Auger
electron spectroscopy study of the interface between bulk
aluminum and bulk aluminum oxide Vittoria Contini,
Carlo Presilla, Francesco Sacchetti, Sergio Tosto
Surf. Science 276, 5058 (1992)
Show Abstract
An extensive Auger electron spectroscopy study of the
aluminumaluminum oxide interface is presented, with the aim
of identifying the behaviour of the contact zone between
bulk metal and bulk oxide. Restored oxygen KLL and aluminum
LVV spectra have been derived and analysed as a function of
the depth of a thick aluminum sample evaporated onto an
aluminum oxide crystal. The capability of the Auger electron
spectroscopy to derive rather unique information on the
nature of the contact zone is used to infer that the metal
and oxide form small isles or domains in the interface
region, so that the transition from the metal to the oxide
is not characterized by a sharp surface.

18 
Chaotic quantum phenomena without classical counterpart
Giovanni JonaLasinio, Carlo Presilla, Federico Capasso
Phys. Rev. Lett. 68, 22692272 (1992)
Show Abstract
We describe a quantum manybody system undergoing multiple
resonant tunneling which exhibits chaotic behavior in
numerical simulations of a meanfield approximation. This
phenomenon, which has no counterpart in the classical limit,
is due to effective nonlinearities in the tunneling process
and can be observed in principle with a heterostructure.

17 
Electron and photon tunneling transducers for gravitational
wave antennae M.F. Bocko, F. Bordoni, M. Karim,
R. Onofrio, C. Presilla, S. Schiller, K.A. Stephenson, N. Zhu
The sixth Marcel Grossmann meeting, edited by H. Sato
and T. Nakamura (World Scientific, Singapore 1992),
p. 14591461
Show Abstract
We show applications of electron and photon tunneling
transducers for detecting small displacements in resonant
bar gravitational wave detectors. A singlecrystal silicon
bar detector of mass 150 kg instrumented with a multimode
tunneling transducer may reach h=6x10^{19} while operating
continuously at room temperature.

16 
Uncertainty principle noise in vacuumtunneling
transducers Carlo Presilla, Roberto Onofrio, Mark
F. Bocko
Phys. Rev. B 45, 37353743 (1992)
Show Abstract
The fundamental sources of noise in a vacuumtunneling probe
used as an electromechanical transducer to monitor the
location of a test mass are examined using a
firstquantization formalism. We show that a tunneling
transducer enforces the Heisenberg uncertainty principle for
the position and momentum of a test mass monitored by the
transducer through the presence of two sources of noise: the
shot noise of the tunneling current and the momentum
fluctuations transferred by the tunneling electrons to the
test mass. We analyze a number of cases including symmetric
and asymmetric rectangular potential barriers and a barrier
in which there is a constant electric field. Practical
configurations for reaching the quantum limit in
measurements of the position of macroscopic bodies with such
a class of transducers are studied.

15 
Continuous quantum monitoring of position of nonlinear
oscillators Michael B. Mensky, Roberto Onofrio,
Carlo Presilla
Phys. Lett. A 161, 236240 (1991)
Show Abstract
Application of the pathintegral approach to continuous
measurements leads to effective Lagrangians or Hamiltonians
in which the effect of the measurement is taken into account
through an imaginary term. We apply these considerations to
nonlinear oscillators with use of numerical computations to
evaluate quantum limitations for monitoring position in such
a class of systems.

14 
Oscillations due to manybody effects in resonant
tunneling Federico Capasso, Giovanni JonaLasinio,
Carlo Presilla
Microscopic aspects of nonlinearity in condensed
matter, edited by A.R. Bishop, V.L. Pokrovsky,
V. Tognetti (Plenum Press, New York, 1991), p. 193196
Show Abstract
The resonant tunneling of electrons through a double barrier
is analyzed from a dynamical point of view. When a self
consistent potential, representing the effect of the
electrostatic feedback induced by the charge trapped in the
well, is taken into account, the nonlinearity of the
transition process can lead to oscillations of the
transmitted fluxes. This behavior is shown to depend
sensitively on the energy spread of the incident electron
distribution and on the intensity of the electrostatic
feedback.

13 
Dynamical analysis of resonant tunneling in presence of a
self consistent potential due to the space charge
Carlo Presilla, Giovanni JonaLasinio, Federico Capasso
Resonant tunneling in semiconductors: physics and
applications, edited by L.L. Chang, E.E. Mendez,
C. Tejedor (Plenum Press, New York, 1991), p. 275284
Show Abstract
The resonant tunneling of electrons through a double barrier
is analyzed from a dynamical point of view. When a self
consistent potential, representing the effect of the
electrostatic feedback induced by the charge trapped in the
well, is taken into account, the nonlinearity of the
transition process can lead to oscillations of the
transmitted fluxes. This behavior is shown to depend
sensitively on the energy spread of the incident electron
distribution and on the intensity of the electrostatic
feedback.

12 
Nonlinear feedback oscillations in resonant tunneling through
double barriers Carlo Presilla, Giovanni
JonaLasinio, Federico Capasso
Phys. Rev. B 43, 52005203 (1991)
Show Abstract
We analyze the dynamical evolution of the resonant tunneling
of an ensemble of electrons through a double barrier in the
presence of the selfconsistent potential created by the
charge accumulation in the well. The intrinsic nonlinearity
of the transmission process is shown to lead to oscillations
of the stored charge and of the transmitted and reflected
fluxes. The dependence on the electrostatic feedback induced
by the selfconsistent potential and on the energy width of
the incident distribution is discussed.

11 
Cold
fusion one year after Roberto Battiston, Carlo
Presilla
Problems of fundamental modern physics, II, edited by
R. Cherubini, P. Dalpiaz, B. Minetti (World Scientific,
Singapore, 1991), p. 230256
Show Abstract
The one year long history of cold fusion is critically
reviewed on the basis of the more recent results, in an
attempt to establish the perspectives of this field.

10 
Surface effects in Si Auger spectrum Vittoria
Contini, Carlo Presilla, Francesco Sacchetti
Phys. Rev. Lett. 64, 1844 (1990)
Show Abstract
A Comment on the Letter by S. M. Durbin and T. Gog,
Phys. Rev. Lett. 63, 1304 (1989).

9 
Pair
interaction energy of hydrogen isotopes in metallic
lattices. Estimate of fusion rates. Fabio
Marchesoni, Carlo Presilla, Francesco Sacchetti
Europhys. Lett. 10, 493498 (1989)
Show Abstract
The fusion rates for the reactions pd, dd and pp in a
solidstate environment are determined under the assumption
that the fusion process is mediated by bound states of the
reactant pair. An effective binding potential which accounts
for lattice, electronic and pair interactions is envisaged
to model plausible equilibrium and nonequilibrium
conditions. Our estimates for the upperbound fusion rates
in condensed matter lie well below the actual experimental
limits.

8 
Periodically timemodulated bistable systems: stochastic
resonance Luca Gammaitoni, Elisa MenichellaSaetta,
Sergio Santucci, Fabio Marchesoni, Carlo Presilla
Phys. Rev. A 40, 21142119 (1989)
Show Abstract
We characterize the notion of stochastic resonance for a
wide class of bistable systems driven by a periodic
modulation. On developing an adiabatic picture of the
underlying relaxation mechanism, we show that the intensity
of the effect under study is proportional to the escape rate
in the absence of perturbation. The adiabatic model of
stochastic resonance accounts for the role of finite damping
and finite noise correlation time as well. Our predictions
compare well with the results of analogue simulation.

7 
Periodically timemodulated bistable systems: nonstationary
statistical properties Carlo Presilla, Fabio
Marchesoni, Luca Gammaitoni
Phys. Rev. A 40, 21052113 (1989)
Show Abstract
The relaxation properties of a onedimensional overdamped
system modulated by an external periodic force are studied
analytically by means of a perturbation approach. The
validity of the approximations introduced is discussed in
detail. The nonstationary nature of the process is
illustrated by evaluating explicitly the autocorrelation
function for the relaxation in a bistable potential. The
predictions thus obtained are shown to compare favorably
with the results of analogue simulation for the case of a
quartic doublewell potential. The stochastic resonance
mechanism is proven to set in only when the periodic
perturbation breaks the symmetry of the bistable potential.

6 
Classical diffusion in soft potentials and supersymmetric
quantum mechanics Fabio Marchesoni, Pasquale
Sodano, Paolo Biccheri, Carlo Presilla, Marco Zannetti
J. Physique C 3, 5357 (1989)
Show Abstract
We review the use of supersymmetric quantum mechanics in the
analysis of the classical diffusion of a brownian particle
in weakly binding (soft) potentials. In particular, our
computations are shown to provide an accurate analytical
determination of the shapemode frequency of the static
double sineGordon kink.

5 
Supersymmetry and actiation rates Fabio Marchesoni,
Carlo Presilla, Pasquale Sodano
Phys. Lett. A 134, 465468 (1989)
Show Abstract
The supersymmetric connection between FokkerPlanck and
Schrödinger equations is utilized to reduce the
computation of the activation rate in onedimensional
bistable potentials to variational calculation for the
ground state level of a monostable quantum system. The
results thus obtained are compared with the predictions of
conventional approximate techniques for a class of weakly
binding (soft) potentials.

4 
On the
temperature dependence of the LVV Auger spectrum in
vanadium Vittoria Contini, Carlo Presilla,
Francesco Sacchetti
Solid
State Comm. 69, 439442 (1989)
Show Abstract
In absence of structural or electronic transitions, the
temperature dependence of the inelastic energy losses of
escaping electrons is proved to account for most of the
temperature dependence of the raw LXX Auger spectrum in
vanadium. This effect is expected to be true in general.

3 
On the
restoration of Auger line shapes Vittoria Contini,
Carlo Presilla, Francesco Sacchetti
Surf. Science 210, 520531 (1989)
Show Abstract
A simple and efficient method to deduce the true Auger
spectrum from the raw data is presented. This method is an
application to Auger spectroscopy derived from signal
processing procedures employed in different fields. It appears
particularly promising when complex spectra are analyzed as it
avoids spurious information to be introduced. The method is
also compared with the morestandard van Cittert's
approach. An experimental check of the common assumption that
an Auger electron experiences almost the same energyloss
mechanisms as a nearly elastically reflected primary electron
at the same energy is given.

2 
CVV
Auger line shapes in aluminium Vittoria Contini,
Carlo Presilla, Francesco Sacchetti
Solid
State Comm. 70, 851853 (1989)
Show Abstract
Aluminium L_{23} VV and KVV Auger spectra are
compared for the first time. In spite of the differences in
kinetic energy of the escaping electrons and of the
coreholes, the two spectra look very similar suggesting that
surface effects do not contribute much to the Auger
transition. Moreover in both spectra it is visible a high
energy structure which is interpreted as an intrinsic
plasmongrain satellite due to the corehole relaxation.

1 
Auger
spectra of 3d transition metals with orbital degeneracy
Carlo Presilla, Francesco Sacchetti
J. Phys. F 17, 779785 (1987)
Show Abstract
The equation of motion approach is employed to derive the
twobody Green function, relevant for the calculation of Auger
spectra, in the case of systems well described by the Hubbard
Hamiltonian with many bands. The results have been used to
calculate the M_{1}VV (M_{1} valencevalence)
Auger rate of copper, which has been shown to be well
described by the present theory, as distinct contributions
belonging to different bands are clearly present.


Effetti dinamici nel tunneling risonante di elettroni in
microstrutture semiconduttrici Tesi di Dottorato
Show Abstract
In questa tesi viene presentato lo studio della evoluzione
temporale del tunneling risonante di elettroni attraverso
microstrutture semiconduttrici. In particolare, si mostra
che l'interazione elettronica è in grado di indurre
un comportamento oscillante nel tempo delle correnti
trasmesse e riflesse. Tali oscillazioni hanno un periodo
variabile tra 10^{14} e 10^{12} secondi e
la loro esistenza è suscettibile di verifica
sperimentale. Il fenomeno è di rilevanza tecnologica
per la progettazione di dispositivi elettronici molto piu`
veloci di quelli realizzabili attualmente. Esso, inoltre,
presenta un interesse concettuale in quanto costituisce un
esempio di transiente quantistico con proprietà che
non hanno riscontro classico. Nel capitolo 1 si introduce
criticamente la fisica del trasporto quantistico in
eterostrutture semiconduttrici suggerendone una
interpretazione rigorosa in termini di potenziali ed
equazioni efficaci allo scopo di evidenziare alcune
incongruenze, quali quella di una massa efficace variabile,
che potrebbero sorgere da una schema di tipo
fenomenologico. Nel capitolo 2 viene discussa una equazione
di Schrödinger non lineare che descrive, nel limite di
campo medio, il tunneling risonante di un sistema di
elettroni mutuamente interagenti. Si illustra in dettaglio
l'evoluzione temporale del processo e il conseguente
comportamento oscillante della carica dinamicamente
intrappolata negli stati risonanti. L'approfondimento del
fenomeno delle oscillazioni in relazione ad una possibile
indagine sperimentale e l'analisi di alcune situazioni
fisiche di particolare interesse, quali i sistemi dotati di
risonanze multiple e i sistemi magnetici, costituiscono,
infine, l'argomento del capitolo 3.


Studio delle funzioni di Green a due particelle in sistemi di
molti fermioni interagenti: applicazione alle transizioni
Auger CVV nei metalli Tesi di Laurea
Show Abstract
