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May 2017
Gábor Takács: Dynamical confinement in out-of-equilibrium quantum systems
Non-equlibrium quantum systems have recently come to the fore in theoretical physics, mainly due to the rapid development of experimental techniques. The interest is partly motivated by fundamental theoretical problems: what are the conditions for a closed non-equilibrium quantum system to evolve towards an equilibrium, and what is the nature of an eventual equilibrium state? Another reason is that a large number of exotic quantum phenomena, hitherto only predicted or known theoretically, have been realised in the lab, which allows…
Find out more »June 2017
Thomas Seligman: Conduction in realistic graphene related nano-structures: Tight bindng, Microwave experiments and outlook to many-body calculations
We present recent microwave experiments and corresponding tight binding calculations for acetylene and carbon nano-strips. In particular we focus on band gaps near the Dirac point and its sensitivity to the details of the connections. Finally we shall briefly discuss the perspectives of making effective many-body calculations by extending the techniques developed for the extension DFT-based programs to transport. * Thomas Seligman, Centro Internacional de Ciencias, Cuernavaca
Find out more »July 2017
Szabolcs Vajna: Replica resummation of the Baker-Campbell-Hausdorff series
We developed a novel perturbative expansion for the effective Hamiltonian governing the dynamics of periodically kicked systems in the small parameter of the kick strength. The expansion is based on the replica trick, and is formally equivalent to the infinite resummation of the Baker-Campbell-Hausdorff series in the non-kicked Hamiltonian, while taking finite order terms in the kicks. As an application of the replica expansion, we study the heating properties of a periodically kicked spin chain. We demonstrate that even away…
Find out more »Mohammad Ali Rajabpour: Formation probabilities, Post-measurement entanglement entropy and Casimir effect
I will first introduce formation probability as a quantity which can determine the universality class of a quantum critical system. In other words, by calculating this quantity one can find the central charge and critical exponents of a quantum system and determine the universality class uniquely. I will show that calculating this quantity boils down to finding Casimir energy of two needles. Then using boundary conformal field theory (BCFT) techniques we find exact results for the formation probabilities. Numerical results…
Find out more »August 2017
J. M. P. Carmelo: One-electron spectral functions of low-dimensional systems accounting for finite-range interactions
A transformation that accounts for the universality found in Ref. concerning the finite energy behavior of dynamical correlation functions of both integrable and non-integrable 1D correlated systems is used to generate from the pseudo-fermion dynamical theory of the integrable 1D Hubbard model a corresponding renormalized theory with additional electron finite-range interactions . The obtained renormalized theory is used to describe the experimental spectral lines in the angle resolved photoemission spectroscopy of the 1D quantum line defects in the 2D van…
Find out more »October 2017
Marin Bukov: The Phases of Quantum Control
The ability to prepare a physical system in a desired quantum state is central to many areas of physics such as nuclear magnetic resonance, cold atoms, and quantum computing. Preparing states quickly and with high fidelity remains a formidable challenge. In this work we implement cutting-edge Reinforcement Learning (RL) techniques to find short, high-fidelity driving protocols from an initial to a target state in non-integrable single-particle and many-body quantum spin systems. The quantum state preparation problem, viewed as an optimization…
Find out more »November 2017
Silvia Pappalardi: Scrambling and entanglements spreading in long-range spin chains
Out of Time Ordered Correlators (OTOCs) have been suggested as a probe of scrambling (generically referred as the delocalization of quantum information) and as a measure of chaos in quantum many-body systems. We explore scrambling in connection to entanglement dynamics in generic long-range systems, and in particular in the infinite-range Ising model. We study both bipartite and multipartite entanglement dynamics and we compare the results with the OTOCs of collective spin operators. We argue that scrambling and entanglement growth are two…
Find out more »Carlos Pineda: Generic features of temporal evolution in hierarchical systems
Many complex systems are hierarchical in nature; social groups, economic andbiological ecosystems, transportation infrastructures, languages, they alldevelop hierarchies of their constitutive elements that emerge from networkedinteractions within the system and with the external world. These hierarchieschange in time according to system-dependent mechanisms of interaction, such asselection in evolutionary biology, or rules of performance in human sports, andreflect the relevance or ability of the element in performing a function in thesystem. However, it is still unclear whether the temporal evolution ofhierarchies…
Find out more »Marko Robnik: Application of the WKB method in 1D linear and nonlinear time-dependent oscillators
The WKB method is an important analytic tool for solving numerous problems in mathematical physics of 1D systems, for example the stationary (time-independent) Schrödinger equation in one dimension, or the classical dynamics of one-dimensional time-dependent (nonautonomous) Hamilton oscillators. I shall review the standard WKB method including the exact explicit solutions to all orders, published by Rob- nik and Romanovski (2000), and applied in a series of papers. Among other results we have shown that the application of the method in…
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