9:309:50  Iscrizioni 
9:5010:30  Giuliano Benenti  Università degli Studi dell'Insubria
Coupled particle and heat transport: a dynamical system's perspective
The understanding of coupled particle and heat transport in complex
systems is a fundamental problem, also of practical interest in connection
with the challenging task of developing highperformance thermoelectric
materials. We will discuss thermoelectric transport phenomena from the
perspective of dynamical nonlinear systems [1], focusing on stylized classical
and quantum models, including the disordered hardpoint gas and asymmetric
quantumdot ring structures pierced by an AharonovBohm flux. We will show
that neither energy filtering nor the socalled strong coupling between
particle and energy fluxes are necessary conditions for achieving the Carnot
efficiency.
In particular, we will propose a mechanism for increasing the thermoelectric
figure of merit in interacting systems with a single relevant constant of
motion, typically in momentumconserving systems [2]. Such a general result will
be illustrated by means of a diatomic chain of hardpoint colliding
particles and in a twodimensional multiparticle collision dynamics
model, where the total momentum is the only relevant conserved quantity [23].
We will then focus on systems with broken timereversal symmetry [47], for
which the maximum efficiency and the efficiency at maximum power are
both determined by two parameters: a ``figure of merit'' and an asymmetry
parameter. In contrast to the timesymmetric case, the figure of merit is
bounded from above; nevertheless the Carnot efficiency can be reached at
lower and lower values of the figure of merit and far from the strong coupling
condition as the asymmetry parameter increases. Moreover, the CurzonAhlborn
limit for efficiency at maximum power can be overcome within linear response.
Finally, we will show that a weak magnetic field generally improves either the
efficiency of thermoelectric power generation or of refrigeration, the
efficiencies of the two processes being no longer equal when a magnetic
field is added.
References: [1] G. Benenti and G. Casati, Increasing thermoelectric efficiency: dynamical models unveil microscopic mechanisms, Phil. Trans. R. Soc. A 369, 466 (2011). [2] G. Benenti, G. Casati and J. Wang, Conservation laws and thermodynamic efficiencies, Phys. Rev. Lett. 110, 070604 (2013). [3] K. Saito, G. Benenti and G. Casati, A microscopic mechanism for increasing thermoelectric efficiency, Chem. Phys. 375, 508 (2010). [4] G. Benenti, K. Saito and G. Casati, Thermodynamic bounds on efficiency for systems with broken timereversal symmetry, Phys. Rev. Lett. 106, 230602 (2011). [5] K. Saito, G. Benenti, G. Casati and T. Prosen, Thermopower with broken timereversal symmetry, Phys. Rev. B 84, 201306(R) (2011). law in small molecular wires, Phys. Rev. B 86, 035433 (2012). [6] M. Horvat, T. Prosen, G. Benenti and G. Casati, Railway switch transport model, Phys. Rev. E 86, 052102 (2012). [7] V. Balachandran, G. Benenti and G. Casati, Efficiency of threeterminal thermoelectric transport under brokentime reversal symmetry, preprint arXiv:1301.1570 [condmat.meshall]. 
10:3010:50  Paolo De Gregorio  INFN Padova
On the effect of heat fluxes on the vibrational energy of a solid
Starting from operational concerns in Gravitational Waves detection
attempts, the RareNoise collaboration has devised a few experiments to
determine whether nonequilibrium should be expected to play a role in a
large class of precision measurements. The most impacting result has
been to demonstrate that temperature differences across a macroscopic
oscillator cause a marked increase of the amplitude of the fluctuations
of a few lowfrequency resonant modes. If one were to make use of the
concept of effective temperature, it would mean that to within room
temperature, the equivalent energy stored in those modes is of the order
of 400 and up to 900 K. From another perspective, this may be viewed as
an explicit measurable violation of the energy equipartition principle
induced by a heat flux. Numerical simulation results of a semiopen
linear chain are in agreement with the experimental finding, which can
be explained at the most basic level also theoretically. One assumes
that heat fluxes go hand in hand with an increase of intermodal correlations, which can
sometimes become measurable depending on the strength of the coupling.

10:5011:20  pausa caffè 
11:2012:00  Giuseppe Gonnella  Università degli Studi di Bari
Singular behaviour of heat fluctuations in a quenched ferromagnet
The offequilibrium probability distribution of the heat
exchanged by a ferromagnet in a time interval after a quench below
the critical point is calculated analytically in the large\(N\) limit.
Here \(N\) is the number of components of the vectorial order parameter.
The distribution shows a singular behavior with a critical threshold
below which a macroscopic fraction of heat is released by the \(k=0\)
Fourier mode of the order parameter. The mathematical structure
producing this phenomenon is the same responsible of the order
parameter condensation in the equilibrium low temperature phase. The
heat exchanged by the individual Fourier modes follows a non trivial
pattern, with the unstable modes at small wave vectors warming up
the modes around a characteristic finite wave vector \(k_M\). Two
internal temperatures, associated to the \(k=0\) and \(k=k_M\) modes,
rule
the heat currents through a fluctuation relation similar to the one
for stationary systems in contact with two thermal reservoirs.

12:0012:20  Pietro Coletti  Università di Roma "Roma Tre"
Dynamical metastability in the Potts model The Potts model is a generalization of the Ising model, with \(q\) different state available for every lattice site. For \(q>4\) the system undergoes a first order phase transition, whose control parameter is the temperature. The presence of multiple equilibrium phase can slow down the dynamics towards equilibrium. We investigated the dynamical metastability of the Potts model on a square lattice after a quench just below the discontinuous transition temperature. By mean of the correlation function of the system we identified the metastable realization and we have studied their energy distribution and the dependence of the spinodal temperature with the system size, in order to assert whether or not metastability is a finitesize effect. 
12:2012:40  Matteo Marcuzzi  SISSA Trieste Collective nonequilibrium dynamics in the presence of surfaces
Symmetries can be regarded as nontrivial constraints limiting the
freedom of a physical system. It has to be expected, therefore, that
upon relieving some of those restriction will lead to the emergence of
new phenomena. A fundamental example is provided by space and
timetranslational invariance in statistical systems, which can be
thought to eff ectively hold at a coarsegrained scale and can be broken
by the introduction of boundaries, implemented by surfaces for the
former (an unavoidable feature in any real sample) and, for the latter,
by some initial condition for the dynamics which causes a
nonequilibrium evolution. While the separate e ffects of these two
boundaries are well understood, additional, unexpected features arise
upon approaching the eff ective edge formed by their intersection. In
order to investigate them we have focused on a classical semiinfinite
Ising model evolving out of equilibrium after a temperature quench from
the disordered phase to its critical point. Considering both critical
and tricritical values of the coupling among surface spins, we have
found numerical evidence of a scaling regime with universal features
which emerges upon approaching the spatiotemporal edge and we have
rationalised such findings within a fieldtheoretical approach.
Reference: M. Marcuzzi, A. Gambassi and M. Pleimling, EPL 100, 46004
(2012)

12:4013:00  Federico Corberi  Università di Salerno
Con quale velocità si ordina un sistema disordinato ?
Mentre la cinetica di ordinamento di fase è
un processo relativamente ben compreso in sistemi puri,
la nostra conoscenza di questo fenomeno in mezzi disordinati
è assai più lacunosa. In particolare, per quanto riguarda
la legge di crescita delle regioni ordinate, esistono
risultati contrastanti a favore di leggi logaritmiche
oppure algebriche. Discuterò qual è il meccanismo all'origine
di questi diversi comportamenti.

13:0014:30  pausa pranzo 
14:3015:30  POSTER 
15.3016.10  Arianna Montorsi  Politecnico di Torino
Hidden order beneath the gapped phases of low dimensional fermionic systems The parity order hidden in the Mott insulating phase of 1D bosonic gases was observed via highresolution imaging in optical lattices [1]. In the fermionic case, it was shown in [2] that spin and charge parity orders characterize the two gapped phases of the 1D Hubbard model, suggesting also the possible detection of pairs of fermions with opposite spins on neighboring sites in the Luther Emery phase. The discoveries can be casted into a general result obtained in [3], stating that longrange order is present in every gapped phase of one dimensional fermionic systems. It is captured by twopoint correlators of appropriate charge and/or spin operators of nonlocal type. At least one of them remains asymptotically finite in each gapped phase, vanishing at the transition. We discuss the above findings and give some preliminary result about their generalization to the twodimensional case. In collaboration with M. Roncaglia References [1] M. Endres et al., Science 334 200 (2011) [2] A. Montorsi, and M. Roncaglia, Phys. Rev. Lett. 109, 236404 (2012) [3] L. Barbiero, A. Montorsi, and M. Roncaglia, "How hidden orders generate gaps in 1D fermionic systems", preprint arxiv:1302.6136 
16.1016.30  Davide Valenti  Università di Palermo
Quantum particle in asymmetric bistable potential: transient dynamics and asymptotic behaviour We consider the transient dynamics and asymptotic behaviour of a dissipative multilevel quantum system, consisting of a particle in an asymmetric double well potential. The environment is the thermal bath described by the CaldeiraLeggett model with Ohmic spectral density. The time evolution of the system is studied through the populations, the diagonal elements of the reduced density matrix of the system, in the Discrete Variable Representation (i.e. in a spatially localized basis): they are the solution of a Markovian approximated master equation, derived, in the strong coupling regime, from a discretized double path integral with the FeynmanVernon influence functional. First we evaluate the populations by varying the damping constant i.e. the strength of the coupling with the environment. At higher damping we find a delayed dynamics, due to the quantum Zeno effect. In particular we observe that the population of the metastable state, located in the higher well, reaches its maximum value at later times as the the coupling strength is increased. As a second step, we study the mean escape time (MET) from the metastable state, varying both the bath's temperature and coupling strength. We find that for weaker damping the MET exhibits, as a function of the temperature, a nonmonotonic behavior, which resembles the noise enhanced stability (NES) phenomenon observed in several nonlinear classical systems. Conversely, increasing the coupling strength, the MET becomes independent of the temperature (quantum Zeno effect). We conclude our study considering the presence of an external periodical driving force. We study the time evolution of all populations as a function of the amplitude A and frequency \(\nu\) of the periodical signal, in different damping/temperature regimes. We also analyze the combined effect of the thermal noise and external driving on the longtime behaviour of the system. In particular, we find that both the energy and asymptotic population of the metastable state exhibit a nonmonotonic behaviour as functions of the frequency \(\nu\). 
16.3017.00  pausa caffè 
17.0017.40  Fausto Borgonovi  Università Cattolica Brescia
A quantum biological switch
A linear chain of connected electron sites with two independent sinks, one attached
to each end, is considered as a simple model for a quantum electron transfer
in photosynthetic biocomplexes. Under the condition of a symmetric initial
population in the middle of the chain, it is expected that the efficiency of the
electron
transfer from the middle of the chain to the sinks
is dominated by the sink with the strongest coupling.
However, we show that quantum effects can modify this intuitive ``classical''
mechanism
so that electron transfer can occur through the weaker coupled sink with maximal
efficiency.
Using this capability we show how to make a quantum switch that can transfer an
electron
to the left or right branch of the chain, by changing the coupling to the sinks.
The operational principles of this quantum device are given in term of
superradiance transitions
and subradiant states. When the realistic data are taken from the photosystem II
reaction center,
this quantum biological switch is shown to retain its reliability, even at room
temperature.

17.4018.00  Andrea Carati  Università degli Studi di Milano
Metaequilibrium statistical thermodynamics
Dal teorema di Fluttuazione Dissipazione si ottengono formule per i coefficienti
delle forme differenziali \(\delta Q\) e \(\delta W\) del calore
assorbito e del lavoro
compiuto dal sistema di interesse. Qui dimostriamo che la forma
differenziale
\(\delta Q \delta W\) e' chiusa. Sicché esiste una energia
interna definita da
\( dU= \delta Q \delta W\).

18.0018.20  Matteo Polettini  University of Luxembourg
The gauge symmetry of nonequilibrium thermodynamics
Picking up a thread of discussion initiated at the 15th Pama Seminar, I
will discuss how to reconcile noninvariance of the GibbsShannon
entropy under coodinate transformations with the required invariance of
the laws of thermodynamics, a problem that mingles with that of the
apparent subjectivity of the informationtheoretic approach to
Statistical Mechanics. In particular, I will show how to derive general
features of thermodynamics from a gauge principle, I will discuss the
gauge connection and its curvature, and I will give an application to
the Minimum Entropy Production Priciple.
