2019 seminars |

🔗 Next up |

Quenched or continuously driven quantum systems can show universal dynamics near non-thermal fixed points, generically in the form of scaling behavior in space and time. Key aspects of the theory of non-thermal fixed points will be briefly summarized, as well as recent experimental results for quenched systems. In a dilute Bose gas, universal scaling dynamics can be due to both linear and non-linear excitations of the system. Considering scaling transport of excitations to larger wave numbers similar to an inverse cascade, the underlying excitations can be either irregular phase excitations or (quasi-)topological defects exhibiting the implications for quantum turbulence. As an example, strongly anomalous scaling of inverse transport in a two-dimensional superfluid due to higher-order vortex annihilation will be discussed both from the theoretical and experimental point of view. | ||

📅 🕓 🚪 |
May 14, 2019 11:00 SISSA, Room 5 |
Thomas Gasenzer |
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Universal Dynamics Near Non-Thermal Fixed Points and Quantum Turbulence |

In my talk I will give a review on the logarithmic terms that appear in the entanglement entropy, their relation to conformal anomaly and the geometry of the entangling surfaces. I will discuss how the presence of boundaries may effect these terms. | ||

📅 🕓 🚪 |
May 7, 2019 11:00 SISSA, Room 128 |
Sergey Solodukhin |
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Logarithmic terms in entanglement entropy: black holes, anomalies and boundaries |

The jamming transition in packings of hard particles is of fundamental interest in the physics of granular materials and glasses. In recent years the physics of jamming has gained momentum in several interdisciplinary contexts, going from Machine Learning to Inference, Ecology and beyond. I will introduce the Simplest Model of Jamming and show how jammed points share peculiar critical properties, highly universal and deeply related glass physics. After discussing the implications of the vicinity to jamming in a glassy phase, I will consider the problem of Information Storage in Machine Learning. Going from the single neuron to multilayer networks, the capacity limit becomes a jamming point. | ||

📅 🕓 🚪 |
April 16, 2019 11:00 ICTP, Stasi Room |
Silvio Franz |
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The Paradigm of Jamming: from Low-Temperature Glasses to Machine Learning and more |

We demonstrate for the first time extremely smooth, coherence-preserving matterwave guides based on time-averaged adiabatic potentials (TAAP). We do so by guiding Bose–Einstein condensates (BEC) over macroscopic distances without affecting their internal coherence: We use a novel magnetic accelerator ring to accelerate BECs to more than 16x their velocity of sound. We transport the BECs in the TAAP over truly macroscopic distances (15 cm) whilst preserving their internal coherence. The BECs can also be released into the waveguide with barriers controllable down to 200 pK giving rise to new regimes of tunnelling and transport through mesoscopic channels. The high angular momentum of more than 40000 ħ per atom and high velocities raises interesting possibilities with respect to the higher Landau levels of quantum Hall states of atoms and open new perspectives in the study of superfluidity. Coherent matterwave guides will result in much longer measurement times (here > 4 s) and much increased sensitivity in highly compact devices. This will raise the spectre of compact, portable guided-atom interferometers for fundamental experiments and applications like gravity mapping or navigation. | ||

📅 🕓 🚪 |
April 15, 2019 11:00 SISSA, Room 128 |
Wolf von Klitzing |
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Hypersonic Transport of Bose-Einstein Condensates in a Neutral-Atom Accelerator Ring |

In this talk, I will discuss a semiclassical numerical method, based on a large-S path integral approach, to study systems whose spin liquid behaviour is underpinned by perturbative ring-exchange Hamiltonians. The method can readily access both thermodynamic and spectral properties. I will focus in particular on quantum spin ice and its photon and vison excitations. After benchmarking the method against existing results on photons, I will show how it can be used to characterise visons and their thermodynamic behaviour. We find that visons form a weak electrolyte — in contrast to spinons in classical spin ice. That is, vison pairs are the dominant population at low temperatures. This is reflected in the behaviour of thermodynamic quantities, such as pinch point motifs in the relevant correlators. Moreover, visons appear to strongly hybridise with the photon background, a phenomenon that likely affects the way these quasiparticles may show up in inelastic response measurements. I will conclude with a brief discussion of the significance of our results and an outlook on further applications of our method. |
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📅 🕓 🚪 |
April 11, 2019 11:00 ICTP, Stasi Room |
Claudio Castelnovo |
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Seeing Beyond the Light: Vison and Photon Electrodynamics in Quantum Spin Ice |

I will present a class of models for quantum chaos in a spatially extended many-body system. It consists of a chain of sites with nearest-neighbour coupling under Floquet time evolution. Quantum states at each site span a q-dimensional Hilbert space and the time evolution is specified as a random circuit, whose local gates are random in space but periodic in time (Floquet). I will discuss a diagrammatic formalism useful to average over realisations of the random circuit.
This approach leads to exact expressions in the large- |
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📅 🕓 🚪 |
March 19, 2019 11:00 ICTP, Stasi Room |
Andrea De Luca |
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Solvable minimal models for many-body quantum chaos |

The simplest model of granular material is a “fluid” made of inelastic hard spheres. For such a system—in the dilute limit—the classical program of kinetic theory Boltzmann equation, Chapman–Enskog-based hydrodynamics has been developed by physicists and mathematicians in the last decades. In this seminar, after recalling a few key results of such a theoretical activity, I will focus on a series of experiments made in my laboratory in the last 5 years. They concern the statistical properties of a massive probe immersed in a steady state granular fluid. The fluid is obtained by vibro-fluidization of a large number of solid spheres of different materials, while the probe is a rigid rotator whose angular displacement and angular velocity are the key observables. In the dilute limit one conjectures a Markovian approximation for the rotator’s dynamics which explains many aspects of the experiment, including a qualitative understanding of “motor effects” in the presence of rotator’s geometrical asymmetries. Further noticeable facts appear when the granular fluid is no more dilute, mainly anomalous diffusion and non-monotonous viscosity. |
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📅 🕓 🚪 |
March 12, 2019 11:00 SISSA, Room 128 |
Andrea Puglisi |
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Granular Brownian Motion |

We study inhomogeneous quenches in integrable models. The Non-Equilibrium Steady State emerging in such systems has been recently conjectured to be described by a Generalised Hydrodynamic theory. We develop a mathematically rigorous method to calculate the asymptotics of observables at large times and distances and show how certain predictions of this conjecture can be derived from analyticity properties of the Slavnov formula for Bethe state overlaps. | ||

📅 🕓 🚪 |
March 5, 2019 11:00 SISSA, Room 128 |
Spyros Sotiriadis |
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Quantum Transport after Inhomogeneous Quenches |

The determination of four-point correlation functions of two-dimensional lattice models is of fundamental importance in statistical physics. In the limit of an infinite lattice, this question can be formulated in terms of conformal field theory (CFT). For the so-called minimal models the problem was solved more than 30 years ago, by using that the existence of singular states implies that the correlation functions must satisfy certain differential equations. This settles the issue for models defined in terms of local degrees of freedom, such as the Ising and 3-state Potts models. However, for geometrical observables in the Fortuin–Kasteleyn cluster formulation of the Q-state Potts model, for generic values of Q, there is in general no locality and no singular states, and so the question remains open. As a warm-up to solving this problem, we discuss which states propagate in the s-channel of such correlation functions, when the four points are brought together two by two. To this end we combine CFT methods with algebraic and numerical approaches to the lattice model. | ||

📅 🕓 🚪 |
February 19, 2019 11:00 SISSA, Room 128 |
Jesper Jacobsen |
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Four-point functions in the Fortuin–Kasteleyn cluster model |

I will present recent work on ferromagnetic quantum Hall states that form on (111) surfaces of elemental Bismuth in high magnetic fields. This unusual states of matter combine the topological features of quantum Hall states with orientational symmetry breaking characteristic of nematic order. Recent scanning tunneling microscopy measurements have directly visualized the spontaneous formation of boundary modes between distinct nematic domains and investigated their electronic structure. I will demonstrate that these boundary modes belong to a new class of `symmetry-protected’ Luttinger liquid that arise from the interplay of symmetry-breaking with quantum Hall physics, and that they provide a concrete realization of ‘anomaly inflow’. The analysis reveals strikingly different behavior of domain wall transport at quantum Hall filling factor ν = 1.2, in striking agreement with the STM results. I will explore implications of these ideas for the global phase diagram of quantum Hall valley nematics. | ||

📅 🕓 🚪 |
January 29, 2019 11:00 ICTP, Stasi Room |
Siddharth Parameswaran |
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Topology, symmetry, and anomalies: investigating domain wall physics in quantum Hall nematic states |

One of the paradigms of quantum mechanics is the statistical nature of measurements: the result of measurements is indeed described by a probability distribution function (PDF), and measuring the same observable in identical systems will give different outcomes in accordance with this distribution. The PDF carries very detailed information about the system, going much beyond the simple average. Here I exploit the Matrix Product Operator (MPO) representation of the Generating Functions to efficiently perform local measurements in one-dimensional spin systems using Tensor Network Methods, both in and out-of-equilibrium. Finally, inspired by such formulation, I show some preliminary results connecting MPS with Neural Network Quantum States. | ||

📅 🕓 🚪 |
January 24, 2019 14:00 SISSA, Room 128 |
Mario Collura |
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Tensor Network Methods for Probability Distribution Functions and beyond… |

Several atomic, molecular, and optical systems, as well as certain condensed matter models, exhibit long-range interactions that decay with distance r as a power law 1/r^{α}. In this talk, we will present recent results for the localization properties of correlation functions of these long-range quantum models in the presence of disorder. The latter is usually associated with exponential localization of wave functions and correlations. We demonstrate that in most situations in 1D power-law interactions imply algebraic decay of correlations. We will discuss the generality of these results and their application to experiments in atomic and molecular physics. |
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📅 🕓 🚪 |
January 22, 2019 11:00 SISSA, Room 128 |
Guido Pupillo |
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Algebraic localization of disordered long-range quantum models |

Quantum optimal control allows one to find the optimal strategy to drive a quantum system into a target state. We review an efficient algorithm to optimally control many-body quantum dynamics and apply it to quantum annealing, going beyond the adiabatic strategy. We present an information theoretical analysis of quantum optimal control processes and its implications. We review some recent advancements we have obtained in tensor network algorithms that enable such investigations and that can be exploited to support the development of quantum technologies via classical numerical simulations: novel approaches to study abelian and non-abelian lattice gauge theories, open many-body quantum systems and systems with long-range interactions or periodic boundary conditions. Finally, we report some theoretical and experimental applications of these approaches to relevant scenarios, such as Rydberg atoms in optical lattices and the gauge theory resulting from the mapping of classical hard problems to short-range quantum Hamiltonians. |
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📅 🕓 🚪 |
January 15, 2019 11:00 ICTP, Stasi Room |
Simone Montangero |
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Optimal control, lattice gauge theories, and quantum annealing |

2018 seminars |

In this talk, I briefly review recent experimental advances in the generation of topological band structures in the non-interacting regime using Floquet engineering and present first studies of interacting atoms in driven 1D lattices. In particular, I will present experimental results obtained with bosonic atoms in driven 1D lattices that directly reveal the existence of parametric instabilities that lead to a depletion of the condensate. Our results point out ways to overcome these limitations in future experiments. In the last part of my talk I will present recent results, where we have used a combination of periodic modulation and strong Hubbard interactions to realize a minimal building block of Z2 lattice gauge theories. We engineer a minimal coupling between matter and gauge fields using two different internal states of bosonic Rb atoms. The obtained lattice model displays local Z2 gauge symmetry, which we study experimentally in a double-well potential – the building block of extended lattice models. |
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📅 🕓 🚪 |
December 18, 2018 11:00 ICTP, Stasi Room |
Monika Aidelsburger |
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Ultracold atoms in periodically-driven optical lattices |

The infrared fixed point of graphene under the renormalization group flow is a relatively under studied yet important example of a boundary conformal field theory with a number of remarkable properties. It has a close relationship with three dimensional QED. It maps to itself under electric-magnetic duality. Moreover, it along with its supersymmetric cousins all possess an exactly marginal coupling — the charge of the electron — which allows for straightforward perturbative calculations in the weak coupling limit. I will review past work on this model and also discuss my own contributions, which focus on understanding the boundary contributions to the anomalous trace of the stress tensor and their role in helping to understand the structure of boundary conformal field theory. | ||

📅 🕓 🚪 |
December 11, 2018 11:00 SISSA, Room 128 |
Christopher Herzog |
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Graphene and Boundary Conformal Field Theory |

Critical lattice models with a non-hermitian Hamiltonian are described by non-unitary CFTs. There are many physical applications such as open quantum systems, geometrical problems or electronic disordered systems. We know that in many cases we can define the notion of effective central charge.I will show why this quantity is important in two problems: the scaling of the entanglement entropy and the identification of universality classes in truncated models. I will illustrate the discussion with examples such as the XXZ model, supersymmetric spin chains, loop models and truncations of the Brownian motion. | ||

📅 🕓 🚪 |
November 27, 2018 11:00 SISSA, Room 128 |
Romain Couvreur |
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Role of the effective central charge in non-unitary conformal field theories |

We study a non-unitary spin chain with orthosymplectic symmetry that generalizes the O(N) model to any positive or negative integer N. The lack of unitarity allows a stable massless Goldstone phase to appear, otherwise forbidden by the Mermin–Wagner theorem, that is described by a supersphere sigma model. On the 2D lattice it is represented as a dense loop model with loop weight N in which crossings are allowed. Unlike the usual O(N) loop model, the presence of crossings makes the model flow to a different regime where correlations involve logarithms. We compute these logarithmic critical exponents with field theory and the Bethe ansatz. | ||

📅 🕓 🚪 |
November 20, 2018 11:00 SISSA, Room 128 |
Etienne Granet |
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A study of a non-unitary statistical model: super spin chains and intersecting loops |

We demonstrate the existence of a new quantum phase of matter that arises in antiferromagnetic spin chains with a weak frustration—just one bond in a large chain. This is the case, for instance, of systems with an odd number of spins with periodic boundary conditions. Such new phase is extended, gapless, but not relativistic: the low-energy excitations have a quadratic (Galilean) spectrum. Locally, the correlation functions on the ground state do not show significant deviations compared to the non-frustrated case, but correlators involving a number of sites (or distances) scaling like the system size display new behaviors. In particular, the von Neumann entanglement entropy is found to follow new rules, for which neither area law applies, nor one has a divergence of the entropy with the system size. Such very long-range correlations are novel and of potential technological interest. We display such new phase in a few prototypical chains using numerical simulations and we study analytically the paradigmatic example of the Ising chain. Through these examples we argue that this phase emerges generally in (weakly) frustrated systems with discrete symmetries. | ||

📅 🕓 🚪 |
November 6, 2018 11:00 SISSA, Room 4 |
Fabio Franchini |
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The Frustration in being Odd: area law violation in local systems |

I will discuss walking behavior in gauge theories and weakly first order phase transition in statistical models. Despite being phenomena appearing in very different physical systems, they both show a region of approximate scale invariance. They can be understood as a theory passing between two fixed points living at complex couplings, which we call complex CFTs. By using conformal perturbation theory, knowing the conformal data of the complex CFTs allows us to make predictions on the observables of the walking theory. As an example, I will discuss the two dimensional Q-state Potts model with Q>4. | ||

📅 🕓 🚪 |
October 16, 2018 11:00 SISSA, Room 4 |
Bernardo Zan |
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Walking behavior, weakly first order phase transitions and complex CFTs |

In this talk, I will discuss an exact mapping between many-body quantum spin systems and classical stochastic processes. This approach can handle integrable and non-integrable systems, including those in higher dimensions, in a unified framework, and can be applied both in and out of equilibrium. Focusing on quantum quenches, I will discuss dynamical quantum phase transitions in the Loschmidt amplitude, showing that these correspond to enhanced fluctuations and other features in the classical stochastic coordinates. | ||

📅 🕓 🚪 |
October 9, 2018 11:00 SISSA, Room 138 |
Stefano De Nicola |
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A Stochastic Approach to Quantum Spin Systems |

We revisit the calculation of multi-interval modular Hamiltonians for free fermions using a Euclidean path integral approach. We show how the multi-interval modular flow is obtained by gluing together the single interval modular flows. Our methods are based on a derivation of the non-local field theory describing the reduced density matrix, and makes manifest its non-local conformal symmetry and U(1) symmetry. We will show how the non local conformal symmetry provides a simple calculation of the entanglement entropy. Time-permitting, we will connect multi-interval modular flows to the frame work of extended quantum field theory. | ||

📅 🕓 🚪 |
September 18, 2018 11:00 SISSA, Room 128 |
Gabriel Wong |
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Gluing together modular flows with free fermions |

Consider a quantum chain in its ground state and then take a subdomain of this system with natural truncated Hamiltonian. Since the total Hamiltonian does not commute with the truncated Hamiltonian the subsystem can be in one of its eigenenergies with different probabilities. Since the global energy eigenstates are locally close to diagonal in the local energy eigenbasis we argue that the Shannon (Rényi) entropy of these probabilities follows an area-law for the gapped systems. When the system is at the critical point the Shannon (Rényi) entropy follows a logarithmic behaviour with a universal coefficient. Our results show that the Shannon (Rényi) entropy of the subsystem energies closely mimics the behaviour of the entanglement entropy in quantum chains. We support the arguments by detailed numerical calculations performed on the transverse field XY chain. | ||

📅 🕓 🚪 |
July 31, 2018 11:10 ICTP, Stasi Room |
Mohammad Ali Rajabpour |
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Area-law and universality in the statistics of the subsystem energy |

Integrated Information Theory (IIT) has emerged as one of the leading research lines in computational neuroscience to provide a mechanistic and mathematically well-defined description of the neural correlates of consciousness. Integrated Information quantifies how much the integrated cause/effect structure of the global neural network fails to be accounted for by any partitioned version of it. The holistic IIT approach is in principle applicable to any information-processing dynamical network regardless of its interpretation in the context of consciousness. In this talk I will describe the first steps towards a possible formulation of a general and consistent version of IIT for interacting networks of quantum systems irrespective of potential applications to consciousness. A variety of different phases, from the dis-integrated to the holistic one can be identified and their cross-overs studied. | ||

📅 🕓 🚪 |
July 3, 2018 11:00 SISSA, Room 128 |
Paolo Zanardi |
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Quantum Integrated Information Theory |

Models for active matter have brought a new type of experiments in statistical physics where the source of nonequilibrium lies within the particles themselves or on their surface. In this talk, I will take the viewpoint of molecular simulations to study matching experiments on chemically-powered anomotors: self-propulsion by symmetry-breaking, chemotaxis, sedimentation and anisotropic nanomotors. I will comment on the design of consistent microscopic models with respect to energy conservation, to chemical kinetic, and to thermal fluctuations. As a perspective, I will discuss enzyme nanomotors. On the one hand, they consist in elaborate catalytic devices with interesting thermodynamic properties and on the other hand they might inspire or serve as molecular scale machine for nano- and bio-technology in the coming years. | ||

📅 🕓 🚪 |
June 19, 2018 11:00 SISSA, Room 128 |
Pierre de Buyl |
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Nanomotors: symmetry, chemotaxis, sedimentation and anisotropy |

The partial transpose of density matrices in many-body systems has been known as a good candidate to diagnose quantum entanglement of mixed states. In particular, it can be used to define the (logarithmic) entanglement negativity for bosonic systems. In this talk, I introduce partial time-reversal transformation as an analog of partial transpose for fermions. This definition naturally arises from the spacetime picture of partially transposed density matrices in which partial transpose is equivalent to reversing the arrow of time for one subsystem relative to the other subsystem. I show the success of this definition in capturing the entanglement of fermionic symmetry-protected topological phases as well as conformal field theories in (1+1) dimensions. | ||

📅 🕓 🚪 |
June 18, 2018 11:00 SISSA, Room 128 |
Hassan Shapourian |
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Partial time-reversal transformation and entanglement negativity in fermionic systems |

The Schur process is in some sense a discrete analogue of a random matrix. Their edge behavior are known to be in the same universality class, described by the Airy kernel and the Tracy–Widom distribution. In this talk we consider two variants of the Schur process: the periodic case introduced by Borodin, and the “free boundary” case recently introduced by us. We are able to compute their correlation functions in a unified manner using the machinery of free fermions. We then investigate the edge asymptotic behavior and show it corresponds to two nontrivial deformations of the Airy kernel and of the Tracy–Widom distribution. Based on joint work with Dan Betea, Peter Nejjar and Mirjana Vuletić. | ||

📅 🕓 🚪 |
May 29, 2018 11:00 SISSA, Room 128 |
Jeremie Bouttier |
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Edge behavior of the periodic and the free boundary Schur processes |

Every physicist has a pretty clear idea of how to define equilibrium phases of matter (e.g. using free energy considerations), whether disordered or ordered (and if ordered, a variety of situations can be encountered). By contrast, dynamics-wise, no generic and clear-cut definition a dynamical phase (disordered, intermittent, uniform, ergodicity-breaking, pattern-forming, etc) can be found. Instead, one works on a system-to-system basis. I will illustrate, on the simple example of a classical system of mutually excluding particles diffusing on a line, how a robust definition of what a dynamical phase is can be achieved. As I will go along, we will see that there may even exist transitions between dynamical phases. On a formal level, these dynamical transitions have everything in common with the quantum phase transitions that appear in hard-condensed matter. I will show that, in turn, approaching quantum problems with a classical eye, can, even with the simple example I’ll discuss, lead to unexpected progress on the quantum side. |
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📅 🕓 🚪 |
May 8, 2018 11:00 SISSA, Room 128 |
Frédéric van Wijland |
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Dynamical phase transitions |

This talk addresses the low energy physics of the Sachdev–Ye–Kitaev model, a paradigm of strongly interacting (Majorana) quantum matter. A salient feature of this system is its exceptionally high degree of symmetry under reparameterizations of physical time. At low energies this symmetry is spontaneously broken and the ensuing infinite dimensional Goldstone mode manifold takes strong influence on all physical observables. We will discuss the effects of these fluctuations on the example of the so-called out of time ordered correlation functions, diagnostic tools to describe both manifestations of quantum chaos in the system and its conjectured duality to an AdS_{2} gravitational bulk. While previous work predicts exponential decay of these correlations in time our main finding is that at large time scales non-perturbative Goldstone mode fluctuations generate a crossover to power law behavior. This phenomenon must have ramifications in the physics of the holographic bulk which, however, we do not understand at present. |
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📅 🕓 🚪 |
April 24, 2018 11:00 ICTP, Stasi Room |
Alex Altland |
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Large Conformal Goldstone Mode Fluctuations in the SYK Model |

The grand canonical ensemble lies at the core of quantum and classical statistical mechanics. A small system thermalizes to this ensemble while exchanging heat and particles with a bath. A quantum system may exchange quantities represented by operators that fail to commute. Whether such a system thermalizes and what form the thermal state has are questions about truly quantum thermodynamics. Here we investigate this thermal state from three perspectives. First, we introduce an approximate microcanonical ensemble. If this ensemble characterizes the system-and-bath composite, tracing out the bath yields the system’s thermal state. This state is expected to be the equilibrium point, we argue, of typical dynamics. Finally, we define a resource-theory model for thermodynamic exchanges of noncommuting observables. Complete passivity — the inability to extract work from equilibrium states — implies the thermal state’s form, too. Our work opens new avenues into equilibrium in the presence of quantum noncommutation. [Based on 1512.01189 with N. Yunger Halpern, P. Faist and J. Oppenheim.] |
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📅 🕓 🚪 |
April 17, 2018 11:00 ICTP, Stasi Room |
Andreas Winter |
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Microcanonical and resource-theoretic derivations of the grand canonical thermal state of a system with non-commuting charges |

In this talk I will describe our work on the simulation of the Schwinger model (i.e. d=1+1 QED) with matrix product states (MPS). I will discuss some systematic aspects of our approach like the truncation of the local infinite bosonic gauge field Hilbert space, or the incorporation of local gauge invariance into the MPS ansatz. Furthermore, I will go through some of our results: the simulation of the particle excitations (“mesons” of confined electron/positron pairs), of string breaking for heavy probe charges and last but not least of the real-time evolution that occurs from a background electric field quench (i.e. the full quantum Schwinger effect). | ||

📅 🕓 🚪 |
March 27, 2018 11:00 ICTP, Stasi Room |
Karel Van Acoleyen |
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Matrix product states for relativistic quantum gauge field theories |

I will first start with a general introduction on theoretical ecology, stressing the reasons that make connections with statistical physics interesting and timely. I will then focus on Lotka–Volterra equations, which provide a general model to study large assemblies of strongly interacting degrees of freedom in many different fields: biology, economy and in particular ecology. I will present our analysis of Lotka–Volterra equations as model of ecosystems formed by a large number of species and show the different phases that emerge. Two of them are particularly interesting: when interactions are symmetric we find a regime characterised by an exponential number of multiple equilibria, all poised at the edge of stability for a large number of species. For non symmetric interactions, this phase is replaced by a chaotic one. I will then conclude discussing relationships with experiments and general consequences of our works. |
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📅 🕓 🚪 |
March 21, 2018 11:00 SISSA, Room 005 |
Giulio Biroli |
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Emergent phenomena in large interacting ecosystems |

I will discuss several recent results, both numerical and analytical, regarding disordered models in external field, focusing mainly on random field ferromagnetic models and spin glasses in a field. I will mainly treat models with Ising variables, but also some new results on XY models will be presented. Exact analytical results are derived for models defined on random graphs under the Bethe approximation, while numerical results are obtained via large scale Monte Carlo simulations for finite dimensional models and via improved message passing algorithms for models on random graphs. | ||

📅 🕓 🚪 |
March 13, 2018 11:00 SISSA, Room 128 |
Federico Ricci-Tersenghi |
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On the complex behavior of disordered models in a field |

In August 1859 the young and still little known Bernhard Riemann presented a paper to the Berlin Academic titled “On the number of primes less than a given quantity”. In the middle of that paper, Riemann made a guess — remark or conjecture — on the zeros of analytic function which controls the growth of the primes. Mathematics has never been the same since. The seminar presents the captivating story behind this problem and discusses how the original conjecture can be extended to all Dirichlet functions, giving rise to the Generalised Riemann Hypothesis for the non-trivial zeros of all these functions. We show that the solution of the Generalised Riemann Hypothesis can be obtained employing ideas and methods which come statistical physics, i.e. from the stochastic world of random walks and alike. |
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📅 🕓 🚪 |
February 28, 2018 11:00 SISSA, Room 128 |
Giuseppe Mussardo |
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The Riemann conjecture |

We study the XXZ spin chain in the presence of a slowly varying magnetic field gradient. First, it is shown that a local density approximation perfectly captures the ground-state magnetization profile. Furthermore, we demonstrate how the recently introduced technique of curved-spacetime CFT yields a very good approximation of the entanglement profile. Finally, the front dynamics is also studied after the gradient field has been switched off. | ||

📅 🕓 🚪 |
February 27, 2018 11:00 SISSA, Room 005 |
Viktor Eisler |
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Entanglement in the XXZ chain with a gradient |

(Boltzmann lecture) I will address one of the fundamental questions in statistical physics: how to conciliate the laws of quantum mechanics for a macroscopic system — which predict a memory of the initial state of the system — with the familiar irreversible phenomena that bring any extended system to a thermal equilibrium, where all memory of the initial state is lost. I will present a series of new results on cold atom quantum systems made of mixtures of fermions, which lead to a physical phenomenon known as Many Body Localization Transition. Moreover, I will discuss the possibility to realize quantum systems with negative temperature in the laboratory. | ||

📅 🕓 🚪 |
February 20, 2018 11:00 SISSA, Room 128 |
Immanuel Bloch |
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Using Ultracold Quantum Gases to Probe New and Old Frontiers of Statistical Physics |

The Tan’s contact is an ubiquitous quantity in systems with zero-range interactions: it corresponds for example to the average interaction energy, to the weight of the tails of the momentum distribution function at large momenta, to the inelastic two-body loss rate, just to cite a few. We focus on strongly interacting one-dimensional bosons at finite temperature under harmonic confinement. As it is associated to short-distance correlations, the calculation of the Tan’s contact cannot be obtained within the Luttinger-liquid formalism. We derive the Tan’s contact by employing an exact solution at infinite interactions, as well as a local-density approximation on the Bethe Ansatz solution for the homogeneous system and numerical ab initio calculations for finite interactions. In the limit of infinite interactions, we demonstrate its universal properties, associated to the scale invariance of the model. We then obtain the full scaling function for arbitrary interactions. | ||

📅 🕓 🚪 |
February 19, 2018 11:00 ICTP, Stasi Room |
Anna Minguzzi |
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Tan’s contact for a strongly interacting one-dimensional Bose gas in harmonic confinement: universal properties and scaling functions |

In this talk I will discuss the motion of a tracer particle driven by an external constant force through a quiescent lattice gas. Due to the interaction between the tracer and the bath particles, here modelled as an exclusion process, the driven tracer reaches a steady-state when the external force and the friction exerted by the bath balance each other. The steady-state is characterised by a non equilibrium broad inhomogeneity of the bath density surrounding the driven tracer yielding a rich variety of behaviours. I show that depending on the effective dimension of the lattice, the driven tracer exhibits from sub-diffusive to strong super-diffusive transport in the limit of high of bath particles. Moreover, when more than one driven tracers exist, the external and friction forces mediate an anisotropic attractive interacting force between the tracers, leading to the formation of clusters. I will show through numerical results that such scenario extends into continuous-space and continuous-time dynamics. | ||

📅 🕓 🚪 |
February 13, 2018 11:00 SISSA, Room 128 |
Carlos Mejía Monasterio |
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Driven tracer in quiescent baths: anomalous diffusion and induced-interaction |

Irreversibility, which is usually quantified by the entropy production, is one of the most fundamental concepts in thermodynamics, with deep scientific and technological consequences. It is also an emergent concept, that stems from the complex interactions between a system and its environment. However, as will be discussed in this talk, the standard theory of entropy production breaks down in the quantum case, in particular in the limit of zero temperature. Motivated by this, I will present recent results which overcome these difficulties using the idea of phase space entropy measures for bosonic systems. As I will show, our theory not only overcomes the zero temperature limitations but also allows one to extend the results to deal with non-equilibrium reservoirs. As an application, we will consider squeezed thermal baths, which are instance of a grand-canonical Generalized Gibbs Ensemble and therefore allow us to construct an Onsager transport theory, akin to the theory of thermoelectricity. Finally, I will also discuss how entropy production emerges from the perspective of the environment and the system environment correlations. | ||

📅 🕓 🚪 |
February 6, 2018 11:00 SISSA, Room 128 |
Gabriel Landi |
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Measures of irreversibility in quantum phase space |

We present a new method to compute Rényi entropies in one-dimensional critical systems using the mapping of the Nth Rényi entropy to a correlation function involving twist fields in a ℤ_{N} cyclic orbifold. When the CFT describing the universality class of the critical system is rational, so is the corresponding cyclic orbifold. It follows that the twist fields are degenerate: they have null vectors. From these null vectors a Fuchsian differential equation is derived, although this step can be rather involved since the null-vector conditions generically involve fractional modes of the orbifold algebra. The last step is to solve this differential equation and build a monodromy invariant correlation function, which is done using standard bootstrap methods. This method is applicable in a variety of situations where no other method is available, for instance when the subsystem A is not connected (e.g. two-intervals EE). |
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📅 🕓 🚪 |
January 30, 2018 11:00 SISSA, Room 128 |
Benoit Estienne |
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Entanglement entropies of 1d critical systems, orbifold and null-vectors |

By the eigenstate thermalization hypothesis (ETH), a highly excited energy eigenstate behaves like a thermal state. It is related to the black hole information paradox by the AdS/CFT correspondence. I will talk about ETH in two-dimensional large central charge CFT and compare the excited state of a primary operator with the thermal state. To define ETH precisely, one needs to know how similar, or equivalently dissimilar, the excited state and thermal state are. I will talk about short interval expansions of the entanglement entropy, relative entropy, Jensen–Shannon divergence. For the canonical ensemble, the excited state and thermal state are the same at the leading order of large central charge and are different at the next-to-leading order. I will also discuss briefly ETH for generalized Gibbs ensemble, and ETH for the descendant excited states. | ||

📅 🕓 🚪 |
January 25, 2018 14:00 SISSA, Room 138 |
Jia-Ju Zhang |
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Eigenstate thermalization hypothesis in two-dimensional large central charge CFT |

In this talk I will motivate the interest for studying SU(N) quantum magnetism, and present three recent results on: i) a microscopic model exhibiting SU(N) chiral spin liquids and their characterization, ii) the phase diagram of SU(N) two-leg spin ladders and iii) finite temperature “phase diagrams” of SU(N) Heisenberg models on two-dimensional lattices. |
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📅 🕓 🚪 |
January 23, 2018 11:00 ICTP, Stasi Room |
Andreas Läuchli |
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SU(N) Quantum Magnetism in 1D and 2D |

Recent experiments on large chains of Rydberg atoms [H. Bernien et al., arXiv:1707.04344] have demonstrated the possibility of realizing 1D systems with locally constrained Hilbert spaces, along with some surprising signatures of non-ergodic dynamics, such as persistent oscillations following a quench from the Neel product state. I will argue that this phenomenon is a manifestation of a “quantum many-body scar”, i.e., a concentration of extensively many eigenstates of the system around special many-body states. The special states are analogs of unstable classical periodic orbits in the single-particle quantum scars. I will present a model based on a single particle hopping on the Hilbert space graph, which quantitatively captures the scarred wave functions up to large systems of 32 atoms. These results suggest that scarred many-body bands give rise to a new universality class of quantum dynamics, which opens up opportunities for creating and manipulating novel states with long-lived coherence in systems that are now amenable to experimental study. | ||

📅 🕓 🚪 |
January 16, 2018 11:00 ICTP, Stasi Room |
Zlatko Papic |
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Quantum Many-body Scars and Non-ergodic Dynamics in the Fibonacci Chain |

Strongly correlated quantum systems exhibit a wide range of phases with unconventional behavior. These phases are characterized by non-trivial global entanglement patterns and cannot be described within the Landau paradigm due to their lack of local order parameters. In my talk, I will discuss how quantum information theory allows us to describe such systems in a way which reconciles their global entanglement with a local description, based on the framework of tensor networks. I will show how tensor networks allow to capture both the structure of the physical interactions as well as global topological entanglement within a unified local description, and how this allows us to build a comprehensive framework to study topologically ordered systems and their excitations. I will then discuss applications of this framework: First, I will show how it allows to characterize the precise nature of topological spin liquids; and second, I will discuss how it can be used to explain topological phase transitions driven by anyon condensation through phases in their entanglement, allowing us to devise measurable order parameters for anyon condensation and thus to study topological phase transitions at a microscopic level. | ||

📅 🕓 🚪 |
January 9, 2018 11:00 ICTP, Stasi Room |
Norbert Schuch |
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Topological Order and Tensor Networks: A Local Perspective on Global Entanglement |

2017 seminars |

📅 🕓 🚪 |
December 19, 2017 11:00 SISSA, Room 128 |
Marco Baiesi |
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Entanglement in protein native states |

📅 🕓 🚪 |
December 12, 2017 11:00 ICTP, Stasi Room |
Matteo Polettini |
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Effective thermodynamics for a marginal observer |

📅 🕓 🚪 |
December 5, 2017 11:00 ICTP, Stasi Room |
Achilleas Lazarides |
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Floquet Systems-Ensembles and Order Under Periodic Driving |

📅 🕓 🚪 |
November 28, 2017 12:00 ICTP, Stasi Room |
Alessandro Vezzani |
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Single big jump and probability condensation in correlated random walks: the case of Lévy Lorentz gas |

📅 🕓 🚪 |
November 14, 2016 11:00 SISSA, Room 005 |
Ingo Peschel |
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The Entanglement Hamiltonian of a Free-Fermion Chain | ||

Watch online |

📅 🕓 🚪 |
November 7, 2017 11:00 SISSA, Room 128 |
Maurizio Fagotti |
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Beyond (first-order) generalized hydrodynamics: why? and how!? |

📅 🕓 🚪 |
October 17, 2017 11:00 SISSA, Room 128 |
Sascha Wald |
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Thermalisation and Relaxation of Quantum Systems | ||

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📅 🕓 🚪 |
October 11, 2017 11:00 SISSA, Room 005 |
Juan R. Gomez-Solano |
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Self-propelled colloidal particles in viscoelastic fluids | ||

Watch online |

📅 🕓 🚪 |
October 4, 2017 11:00 SISSA, Room 128 |
Enrique Rico Ortega |
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Exploring SO(3) “Nuclear Physics” with Ultra-cold Gases |

📅 🕓 🚪 |
September 26, 2017 11:00 SISSA, Big Meeting Room |
Alessandro Codello |
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Functional perturbative RG and CFT data in the ε-expansion | ||

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📅 🕓 🚪 |
September 18, 2017 11:00 ICTP, Stasi Room |
Markus Müller |
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Creating Cool Quantum Matter by Non-linear Driving |

📅 🕓 🚪 |
September 4, 2017 11:00 SISSA, Room 128 |
Fabian H.L. Essler |
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Quantum Master Equations and Integrability |

📅 🕓 🚪 |
June 6, 2017 11:00 ICTP, Stasi Room |
Pranjal Bordia |
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Many-Body Localization Through the Lens of Ultracold Quantum Gases | ||

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📅 🕓 🚪 |
May 23, 2017 11:00 SISSA, Room 138 |
Masud Haque |
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Non-equilibrium dynamics in isolated quantum systems | ||

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📅 🕓 🚪 |
May 4, 2017 11:00 SISSA, Room 138 |
P.K. Mohanty |
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Zeroth law in non-equilibrium — a hot needle in water | ||

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📅 🕓 🚪 |
May 2, 2017 11:00 ICTP, Stasi Room |
G. Biroli |
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Non-Linear Responses, Soft Modes and the True Nature of Glasses | ||

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📅 🕓 🚪 |
April 27, 2017 15:00 SISSA, Room 138 |
S. Sinha |
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Recent developments in Quantum Chaos | ||

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📅 🕓 🚪 |
April 20, 2017 11:00 SISSA, Room 138 |
A. Bernamonti |
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Heavy–Heavy–Light–Light correlators in Liouville theory | ||

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📅 🕓 🚪 |
April 18, 2017 11:00 ICTP, Stasi Room |
R. Moessner |
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Thermodynamics and Order Beyond Equilibrium — The Physics of Periodically Driven Quantum Systems | ||

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📅 🕓 🚪 |
April 12, 2017 14:00 SISSA, Room 138 |
F. Galli |
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Entanglement scrambling in 2d CFT | ||

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📅 🕓 🚪 |
April 11, 2017 11:00 SISSA, Room 128 |
G. Santoro |
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Floquet Topological Insulators? A few warnings | ||

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📅 🕓 🚪 |
March 28, 2017 11:00 SISSA, Room 128 |
F.S. Cataliotti |
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Quantum Control on an Atom Chip | ||

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📅 🕓 🚪 |
March 23, 2017 11:00 SISSA, Room 138 |
N. Pranjal |
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Virasoro coadjoint orbits of SYK/tensor-models & Emergent 2-D Quantum Gravity | ||

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📅 🕓 🚪 |
March 21, 2017 11:00 ICTP, Stasi Room |
A. Rosso |
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Liouville Field Theory and Log-correlated Random Energy Models | ||

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📅 🕓 🚪 |
March 16, 2017 11:00 SISSA, Room 138 |
A. de Quieroz |
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Dualities and Symmetries in the Entanglement Entropy of Fermionic Chains |

📅 🕓 🚪 |
March 14, 2017 11:00 SISSA, Room 128 |
T. Roscilde |
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Quantum correlations: equilibrium and non-equilibrium aspects | ||

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📅 🕓 🚪 |
February 28, 2017 11:00 SISSA, Room 128 |
I. Lesanovsky |
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Exploring far-from-equilibrium physics of dissipative spin systems with highly excited atoms |

📅 🕓 🚪 |
February 21, 2017 12:00 ICTP, Stasi Room |
S. Ciliberto |
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A Protocol for Reaching Equilibrium Arbitrarily Fast |

📅 🕓 🚪 |
February 2, 2017 14:00 SISSA, Room 128 |
J. Viti |
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📅 🕓 🚪 |
January 26, 2017 11:00 SISSA, Room 128 |
G. Parisi |
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The physics of jamming: a journey from marble pebbles toward scaling invariant field theory | ||

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📅 🕓 🚪 |
January 17, 2017 11:00 SISSA, Room 128 |
S. Simon |
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Big Surprises from Small Quantum Hall Droplets | ||

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📅 🕓 🚪 |
January 11, 2017 16:30 SISSA, Room 128 |
N. Defenu |
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Watch online |

2016 seminars |

📅 🕓 🚪 |
November 22, 2016 11:30 SISSA, Room 128 |
M. Serone |
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The Effective Bootstrap |

📅 🕓 🚪 |
November 15, 2016 11:00 SISSA, Room 128 |
G. Mussardo |
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Prime Suspects and Coprime Accomplices: Quantum Tales in Number Theory | ||

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📅 🕓 🚪 |
November 8, 2016 11:00 SISSA, Room 128 |
E. Tartaglia |
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Logarithmic minimal models with Robin boundary conditions | ||

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📅 🕓 🚪 |
October 11, 2016 11:00 SISSA, Room 128 |
M. Mintchev |
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Non-equilibrium quantum transport: quantum heat engines and full counting statistics | ||

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📅 🕓 🚪 |
October 5, 2016 11:00 SISSA, Room 128 |
Huan-Qiang Zhou |
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Fidelity mechanics: analogues of four thermodynamic laws and Landauer’s principle |

📅 🕓 🚪 |
October 4, 2016 11:00 SISSA, Room 005 |
M. Batchelor |
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Free parafermions |

📅 🕓 🚪 |
July 15, 2016 11:00 SISSA, Room 128 |
Z. Zimboras |
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Negativity in free fermion systems | ||

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📅 🕓 🚪 |
July 12, 2016 11:00 SISSA, Room 128 |
V. Eisler |
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Universal front propagation in the XY spin chain with domain wall initial conditions | ||

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📅 🕓 🚪 |
June 28, 2016 11:00 SISSA, Room 128 |
B. Poszgay |
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Quantum quenches and exact correlations in the Heisenberg spin chains | ||

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📅 🕓 🚪 |
June 17, 2016 11:00 SISSA |
A. Lode |
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Fragmentation and correlations of interacting ultracold multicomponent bosons |

📅 🕓 🚪 |
May 26, 2016 11:30 ICTP |
F. Marquardt |
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Light, sound and topology |

📅 🕓 🚪 |
May 24, 2016 11:00 ICTP |
E. Dalla Torre |
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Parametric resonances: from single atoms to many-body systems |

📅 🕓 🚪 |
May 19, 2016 11:00 SISSA, Room 005 |
A. Jakovac |
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Functional renormalization group in fermionic systems | ||

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📅 🕓 🚪 |
May 10, 2016 11:30 SISSA, Room 005 |
R. Egger |
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Multichannel Kondo dynamics and Surface Code from Majorana bound states | ||

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📅 🕓 🚪 |
May 6, 2016 11:30 SISSA, Room 005 |
A. Fring |
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Non-Hermitian quasi-exactly solvable models of E_{2} Lie algebraic type |
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📅 🕓 🚪 |
May 5, 2016 14:30 ICTP, Stasi Room |
U. Schneider |
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📅 🕓 🚪 |
May 3, 2016 11:00 SISSA, Room 005 |
F. Bouchet |
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Large deviation theory applied to climate physics, a new frontier of statistical physics | ||

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📅 🕓 🚪 |
April 28, 2016 11:30 ICTP, Stasi Room |
E. Collini |
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📅 🕓 🚪 |
April 28, 2016 11:00 SISSA, Room 005 |
O.A. Castro-Alvaredo |
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Measures of entanglement from quantum field theory methods | ||

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📅 🕓 🚪 |
April 26, 2016 11:00 SISSA, Room 005 |
B. Doyon |
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Non-equilibrium energy transport at quantum criticality | ||

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📅 🕓 🚪 |
April 22, 2016 14:00 SISSA, Room 005 |
M. Polini |
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Hydrodynamic transport, laminar flow, and the AdS/CFT viscosity bound in a graphene field effect transistor | ||

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📅 🕓 🚪 |
April 20, 2016 15:30 ICTP, Stasi Room |
A. Varlamov |
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📅 🕓 🚪 |
April 15, 2016 14:30 SISSA, Room 005 |
J.M. Stephan |
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Entanglement evolution after inhomogeneous quantum quenches, and the arctic circle | ||

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📅 🕓 🚪 |
April 14, 2016 11:30 ICTP, Stasi Room |
A.K. Heidelberg |
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📅 🕓 🚪 |
April 12, 2016 11:00 SISSA, Room 005 |
J. Dubail |
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Inhomogeneous quantum systems in 1d: how does one describe them with Conformal Field Theory? | ||

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📅 🕓 🚪 |
March 31, 2016 11:30 ICTP, Stasi Room |
E. Vesselli |
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📅 🕓 🚪 |
March 22, 2016 11:00 SISSA, Room 128 |
J. Kurchan |
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Darwinian versus thermal optimization | ||

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📅 🕓 🚪 |
March 18, 2016 15:00 SISSA, Room 005 |
R. Sinha |
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Thermalization with Chemical Potentials, and Higher Spin Black Holes | ||

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📅 🕓 🚪 |
March 17, 2016 11:30 ICTP, Stasi Room |
D. Fausti |
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📅 🕓 🚪 |
March 15, 2016 11:30 SISSA, Room 005 |
S. Diehl |
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Universal Quantum Physics in Driven Open Many-Body Systems | ||

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📅 🕓 🚪 |
March 8, 2016 11:00 SISSA, Room 005 |
G. Sierra |
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Entanglement over the Rainbow | ||

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📅 🕓 🚪 |
March 3, 2016 14:00 SISSA, Room 128 |
C. Maes |
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Driving-induced stability with long-range effects | ||

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📅 🕓 🚪 |
February 22, 2016 14:30 ICTP, Stasi Room |
M. Kruger |
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Fluctuation Induced Interactions In and Out of Equilibrium | ||

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📅 🕓 🚪 |
February 17, 2016 15:00 ICTP |
I. Carusotto |
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📅 🕓 🚪 |
February 16, 2016 11:00 SISSA, Room 128 |
W. Krauth |
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Fast Irreversible Monte Carlo simulations beyond the Metropolis paradigm: Applications to interacting particles and to spin systems | ||

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📅 🕓 🚪 |
February 9, 2016 11:00 SISSA, Room 128 |
T. Fokkema |
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Supersymmetric lattice models: the field theory connection | ||

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📅 🕓 🚪 |
February 2, 2016 11:00 SISSA, Room 128 |
A. Chiocchetta |
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Short-time universality and aging in isolated quantum systems | ||

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📅 🕓 🚪 |
January 26, 2016 11:00 SISSA, Room 128 |
F. Corberi |
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Condensation of large fluctuations in a statistical system |