Topic: 
Quantum Simulation of Abelian and nonAbelian Gauge Theories 
Date: 
23.04.18 
Time: 
16:15 
Place: 
H6 
Guest: 

Bern University 

Abstract: 
Besides Quantum Chromodynamics (QCD) in particle physics, strongly coupled gauge theories arise, for example, in the condensed matter physics of spin liquids, or in the quantum information theory of Kitaev's toric code, which is a Z(2) lattice gauge theory. Numerical simulations of gauge theories on classical computers, in particular, at high fermion density or in outofequilibrium situations, suffer from severe sign problems that prevent the importance sampling underlying Monte Carlo calculations. Quantum simulators are accurately controllable quantum devices that mimic other quantum systems. They do not suffer from sign problems, because their hardware is intrinsically quantum mechanical. Recently, trapped ions, following a laserdriven stroboscopic discrete time evolution through a sequence of quantum gate operations, have been used as a digital quantum simulator for particleantiparticle pair creation in Quantum Electrodynamics. Analog quantum simulators, on the other hand, follow the continuous timeevolution of a tunable model Hamiltonian. Using ultracold atoms in optical lattices, analog quantum simulators have been designed for Abelian and nonAbelian lattice gauge theories. Their experimental realization is a challenge for the foreseeable future, which holds the promise to access the realtime dynamics of string breaking, the outofequilibrium decay of a false vacuum, or the evolution of a chiral condensate after a quench, from first principles. Quantum link models which realize gauge theories including QCD not with classical fields but with discrete quantum degrees of freedom, are ideally suited for implementation in quantum matter. For example, alkalineearth atoms, whose nuclear spin represents an SU(N) degree of freedom, naturally embody fermionic constituents of gluons. CP(N1) models, which are toy models for QCD, can be quantum simulated in a similar way via SU(N) quantum spin ladders. 
Contact person: 
Topic: 
Complex Langevin simulations of a finite density matrix model for QCD 
Date: 
12.04.18 
Time: 
14:15 
Place: 
D6135 
Guest: 
Savvas Zafeiropoulos 
Univ. Heidelberg 

Abstract: 
We study the Stephanov model, which is an RMT model for QCD at finite density, using the Complex Langevin algorithm. The Langevin algorithm (Stochastic Quantization) is not based on Markov Chain Monte Carlo methods and consequently does not suffer from the infamous sign problem that hampers studies at finite baryon density. Naive implementation of the algorithm shows convergence towards the phase quenched or quenched theory rather than to the intended theory with dynamical quarks. A detailed analysis of this issue and a potential resolution of the failure of this algorithm are discussed. We study the effect of gauge cooli! ng on the Dirac eigenvalue distribution and time evolution of the norm for various cooling norms, which were specifically designed to remove the pathologies of the complex Langevin evolution. The cooling is further supplemented with a shifted representation for the random matrices. Additionally, we study the newly proposed deformation technique and a novel form of reweighting. 
Contact person: 
Topic: 
High Spin Cycles: Topping the Spin Record for a Single Molecule verging on Quantum Criticality 
Date: 
26.04.18 
Time: 
14:15 
Place: 
D5153 
Guest: 
Jürgen Schnack 
Universität Bielefeld 

Abstract: 

Contact person: 
Topic: 
Eigenvectorrelated correlation functions and their connection with generalized chiral random matrix ensembles with a source 
Date: 
11.01.18 
Time: 
16:00 
Place: 
D5153 
Guest: 
Jacek Grela 
LPTMS Université ParisSud 

Abstract: 
We will introduce eigenvectorrelated correlation functions, discuss briefly their significance in dynamical Ginibre ensemble [1,2] and present asymptotic results in the large matrix size limit. Motivated by recent work [3] on joint eigenvectoreigenvalue correlation function valid for finite matrix size N in the complex and real Ginibre Ensembles, we study integrable structure of a certain generalized chiral Gaussian Unitary Ensemble with a source [4]. This model can be also interpreted as a deformation of the complex Ginibre Ensemble with an external source with additional determinant term. We present compact formulas for the characteristic polynomial, inverse characteristic polynomial and the kernel. In the case of a special source, we calculate asymptotics in the joint "bulkedge" regime of all aforementioned objects and show their Besseltype behaviour. References: [1] ''Dysonian dynamics of the Ginibre ensemble'', Z. Burda, J. Grela, M. A. Nowak, W. Tarnowski, P. Warcho?, Phys. Rev. Lett. 113, 104102 (2014) [2] ''Unveiling the significance of eigenvectors in diffusing nonhermitian matrices by identifying the underlying Burgers dynamics'', Z. Burda, J. Grela, M. A. Nowak, W. Tarnowski, P. Warcho?, Nucl. Phys. B 897, 421 (2015) [3] ''On statistics of biorthogonal eigenvectors in real and complex Ginibre ensembles: combining partial Schur decomposition with supersymmetry'', Y. V. Fyodorov, arXiv:1710.04699 [4] ''On characteristic polynomials for a generalized chiral random matrix ensemble with a source", Y. V. Fyodorov, J. Grela, E. Strahov, arXiv:1711.07061 
Contact person: 
Topic: 
tba 
Date: 
02.05.18 
Time: 
16:15 
Place: 
V3201 
Guest: 
Paulino Monroy Castillero 
Cuernavaca 

Abstract: 

Contact person: 