9:3010:00  registration 
10:0010:40  Paolo Politi  CNR ISC Firenze
Ground state search in artificial spinice
Artificial spinices are two dimensional arrays of singledomain, Ising
type magnetic dots, whose size is too large to undergo thermal
fluctuations. Therefore, they are strongly outofequilibrium systems
whose dynamics are due to the driving magnetic field and to magnetostatic
interactions among dots.
Square spinices have a well defined ground state, in spite of
frustration. Much work is addressed to understand how the system can be
driven towards the ground state and how dynamics proceeds under the
application of a magnetic field. We give some answers, giving a
description of dynamics in terms of vertex configurations [1] and
highlighting the importance of disorder and randomness [2]: quenched
disorder in the system and randomness in the time dependence of the
driving field.
In collaboration with Zoe Budrikis and Robert L. Stamps (University of Western Australia and University of Glasgow). [1] Phys. Rev. Lett. 105, 107201 (2010). [2] Phys. Rev. Lett. 107, 217204 (2011). 
10:4011:00  Antonio Lamura  CNR IAC Bari
Semiflexible polymers under external fields
We have numerically investigated by using Brownian dynamics, semiflexible
polymers confined in a plane in two cases: under an external force for a
tethered chain and in shear flow for a free one.
Such situations are relevant for adsorbed biological filaments.
Our results confirm experimental results and extend earlier theoretical
predictions.

11:0011:20  Simona Olmi  CNR ISC Firenze
Collective dynamics in sparse networks
The dynamics of sparse networks is investigated both at the
microscopic and macroscopic level, upon varying the connectivity. In
all cases (chaotic maps, StuartLandau oscillators, and leaky
integrateandfire neuron models), we find that a few tens of random
connections are sufficient to
sustain a nontrivial (and possibly irregular) collective dynamics. At
the same time, the microscopic evolution turns out to be extensive,
both in the presence and absence of a macroscopic evolution. This
result is quite remarkable, considered the nonadditivity of the
underlying dynamical rule. 
11:2011:50  coffee break 
11:5012:10  Claudio Borile  Università di Padova
Spontaneously Broken Neutral Symmetry
Spontaneous symmetry breaking plays a fundamental role in many
areas of condensed matter and particle physics. A fundamental
problem in ecology is the elucidation of the mechanisms responsible
for biodiversity and stability. Neutral theory, which makes the
simplifying assumption that all individuals (such as trees in a tropical
forest) –regardless of the species they belong to–
have the same prospect of reproduction, death, etc., yields gross
patterns that are in accord with empirical data. We explore the
possibility of birth and death rates that depend on the population
density of species while treating the dynamics in a species symmetric
manner. We demonstrate that the dynamical evolution can lead to a
stationary state characterized simultaneously by both biodiversity and
spontaneously broken neutral symmetry.

12:1012:30  Jacopo Grilli  Università di Padova
Spatial distribution of species across scales as an emerging pattern
There has been a considerable effort to understand and quantify the
spatial distribution of species across different ecosystems. The Species
Area Relationship (SAR), which relates the area with the number of species
that it supports, is probably one of the most studied quantity in ecology.
We introduce a simple phenomenological model based on Poisson cluster
processes which allows us to derive an analytical expression for the SAR
which reproduces the empirical behavior as sample area increases from
local to continental scales, explaining how it can be understood in terms
of simple geometric arguments. Within our framework we also obtain
interesting prediction for other spatial ecological quantities.

12:3012:50  Mikko Alava  Aalto University
Deciding about manuscripts: the dynamics of refereeing
tba

12:5014:30  lunch break 
14:3015:30  poster session 
15:3015:50  Thomas, Michaels, ETH Zurich
Thermal fluctuations and domain walls in ultrathin magnetic nanowires
The possibility of inducing domainwall (DW) motion in magnetic
nanowires by means of spin polarised electric currents has recently renewed
theoretical interest in this field. The problem is usually modelled
on a micromagnetic approach, but ignoring any thermal fluctuations.
However, some relevant experimental facts  like the correct order of magnitude of the critical current needed for DW motion  still lack
satisfactory
explanations. We thus developed a general theoretical framework, which
highlights the crucial role played by thermal fluctuations at the centre
of
DWs. The latter qualitatively and quantitatively accounts for a variety
of problems relating to DWs at finite temperatures. Examples are the
shrinking of magnetic domains observed in Fe ultrathin
films on Cu(001)
substrates with increasing temperature, the inverse symmetry breaking in
ultrathin films
and the renormalisation of the critical current for
domain
wall motion at finite
temperatures.

15:5016:10  Ruggero Vaia, CNRISC Firenze
Transmitting a quantum state over an arbirarily long uniform channel with
almost perfect quality
An effective onedimensional hopping model can be realized in several
systems, such as spin chains, arrays of quantum dots or optical lattices.
Each site of the array can be thought of as a `qubit', i.e. an object
endowed with a 2dimensional Hilbert space of states, and the natural
dynamics of such an open chain of qubits can be exploited for transferring
a quantum state between its ends, a task which is required for connecting
registers in a quantum computer. Indeed, assuming that the first qubit is
initially in a given state, the purpose of state transfer is that the
dynamics of the chain leads at some time the same state to belong to the
qubit sitting on the opposite end.
In a uniform chain (with uniform hopping amplitudes) the quantumtransfer process is found to be impossible due the effect of dispersion. It is known that perfect transmission can occur if the hopping amplitudes are properly modulated along the channel; however, such an engineered setup is not likely to be realizable in a lab. Therefore we consider a chain with uniform hopping amplitudes and just allow the two extremal pairs of them to be weaker. Surprisingly, provided that the extremal couplings have suitable optimal values depending on the channel length, our setup gives an extremely high transfer quality, with average fidelity larger that 0.99 even in the limit of an infinitely long channel. The transmission time is ballistic and the quality of quantum transfer keeps being high in a large neighborhood of the optimal values so there is no need to finely tune the extremal hopping amplitudes in an experiment. 
16:1016:30  Roberto Franzosi  CNR ISC Firenze
Stati localizzati e a temperatura negativa nell'equazione non
lineare di Schrödinger discretizzata
Le applicazioni degli atomi ultrafreddi, in diversi settori della
fisica, sono
in continua crescita. Ciò è dovuto alla grande
versatilità che
questi sistemi
fisici offrono. L'alto grado di controllo con cui essi possono
essere "preparati", le nuove possibilità di osservazione (in
situ) sviluppate, ed il fatto che la
fisica che sta alla loro base consenta di interpolare tra regimi
dinamici che
vanno da quelli più fortemente quantistici a quelli
classici, li
rendono
dei sistemi fisici "speciali".
Oggigiorno i gas di atomi ultrafreddi trovano applicazione
nell'ambito
dell'informazione quantistica, sono stati proposti come sistemi per
realizzare simulatori quantistici, per esempio di teorie di campo
relativistiche.
Nel presente intervento vedremo come condensati in reticoli ottici
e nel
regime superfluido, possano essere utilizzati nell'ambito della
meccanica
statistica per realizzare stati dinamici localizzati ("breathers")
e
stati termodinamici a temperature negative.
In particolare vedremo che l'equazione non lineare di
Schrödinger
discretizzata, che
descrive appunto la dinamica nel regime superfluido di condensati
in un
reticolo ottico, presenta una regione dei parametri dove tale
sistema evolve
verso uno stato caratterizzato da una densità finita di
"breathers" e una
temperatura negativa. Tale stato è metastabile ma converge
verso
quello di
equilibrio su scale di tempo astronomiche. Stati stazionari a
temperatura
negativa sono sperimentalmente accessibili sfruttando meccanismi di
dissipazione, o tramite un'espansione libera di pacchetti
inizialmente a
temperatura positiva.
S. Iubini, R. Franzosi, R. Livi, G.L. Oppo and A. Politi, "Negative Temperature States in the Discrete Nonlinear Schroedinger Equation", in preparazione. R. Franzosi, "Geometric microcanonical thermodynamics for systems with first integrals", Phys. Rev. E 85, 050101 (2012). R. Franzosi, R. Livi, GL. Oppo, and A Politi, "Discrete Breathers in BoseEinstein Condensates", Nonlinearity 24, R89 (2011). R. Franzosi, "Microcanonical entropy and dynamical measure of temperature for systems with two first integrals", J. Stat. Phys. (2011) 143: 824830. R. Livi, R. Franzosi and G.L. Oppo, "Selflocalization of BoseEinstein condensates in optical lattices via boundary dissipation", Phys. Rev. Lett. 97, 060401 (2006). 
16:3017:00  coffee break 
17:0017:40  Silvio Franz  LPTMS Université Paris Sud Orsay
Viaggio di andata e ritorno tra i Liquidi Vetrosi e la Teoria dei Campi.
La ricerca degli ultimi anni ha enfatizzato il ruolo delle
fluttuazioni e della crescita di correlazioni nella descrizione della
dinamica dei liquidi
vetrosi. In tale contesto è possibile invocare universalità
statistica e descrivere le proprietà dinamiche dei liquidi in
termini
di teorie di campo efficaci. Discuterò 1) come ricavare tali teorie
efficaci a partire dalla teoria microscopica. 2) alcune predizioni e
conseguenze della teoria.
Basato su lavori in collaborazione con G. Parisi, F. RicciTersenghi, T. Rizzo, P.F. Urbani e F. Zamponi 
17:4018:00  Miguel Berganza, IPCFCNR Roma
Criticality of continuous spin models in random graphs. A MonteCarlo
parallel algorithm in GPUs.
We have developed a parallel GPUbased MonteCarlo algorithm devoted to
the analysis of continuous spin models in disordered graphs. This tool
facilitates the study of the critical behaviour of the XY model on a Levy
graph, such that the bond probability decays as a power, rho, of the
distance between bonds with respect to their position in a given
(shortrange) lattice. Varying rho from infinity to zero, the Levy graph
interpolates between the lattice and the uncorrelated (ErdosRany) graph.
Renormalization group arguments allow to define three regimes of rho in
correspondence with different critical behaviours of the model: for
sufficiently low rho the model presents a phase transition of the
meanfield type, whether for large values of rho the transition is
supposed to belong to the KosterlitzThouless universality class. We
provide numerical support of these results, which are in agreement with
previous
studies of the XY model in complex topologies (Cassi, Phys. Rev. Lett. 68
3631 (1992)). Our research is motivated by the study of continuous spin
models with disordered, longrange interactions, relevant in the
statistical description of modes in random lasers (Conti and Leuzzi Phys.
Rev. E 83 134204 (2011)).
