Extended scaling for ferromagnetic Ising models with zero-temperature transitions (2008)
Katzgraber, Helmut G., Campbell, I. A., Hartmann, A. K.
We study the second-moment correlation length and the reduced susceptibility of two ferromagnetic Ising models with zero-temperature ordering. By introducing a scaling variable motivated by...
Quantum annealing for problems with ground-state degeneracy (2008)
Matsuda, Yoshiki, Nishimori, Hidetoshi, Katzgraber, Helmut G
We study the performance of quantum annealing for systems with ground-state degeneracy by directly solving the Schr\"odinger equation for small systems and quantum Monte Carlo simulations for larger...
Ultrametricity and clustering of states in spin glasses: A one-dimensional view (2008)
Katzgraber, Helmut G., Hartmann, Alexander K.
We present results from Monte Carlo simulations to test for ultrametricity and clustering properties in spin-glass models. By using a one-dimensional Ising spin glass with random power-law...
Density of States and Critical Behavior of the Coulomb Glass (2008)
Surer, Brigitte, Katzgraber, Helmut G., Zimanyi, Gergely T., Allgood, Brandon A., Blatter, Gianni
We present zero-temperature simulations for the single-particle density of states of the Coulomb glass. Our results in three dimensions are consistent with the Efros and Shklovskii prediction for the...
ENCORE: An Extended Contractor Renormalization algorithm (2008)
Albuquerque, A. Fabricio, Katzgraber, Helmut G., Troyer, Matthias
Contractor Renormalization (CORE) is a real-space renormalization group method to derive effective Hamiltionians from microscopic models. The original CORE method is based on a real-space...
Evidence for universal scaling in the spin-glass phase (2008)
Jorg, Thomas, Katzgraber, Helmut G.
We perform Monte Carlo simulations of Ising spin-glass models in three and four dimensions, as well as of Migdal-Kadanoff spin glasses on a hierarchical lattice. Our results show strong evidence for...
New Insights from One-Dimensional Spin Glasses (2008)
Katzgraber, Helmut G., Hartmann, Alexander K., Young, A. P.
The concept of replica symmetry breaking found in the solution of the mean-field Sherrington-Kirkpatrick spin-glass model has been applied to a variety of problems in science ranging from biological...
Jorg, Thomas, Katzgraber, Helmut G.
We study the four-dimensional Ising spin glass with Gaussian and bond-diluted bimodal distributed interactions via large-scale Monte Carlo simulations and show via an extensive finite-size scaling...
Pelikan, Martin, Katzgraber, Helmut G., Kobe, Sigismund
This study focuses on the problem of finding ground states of random instances of the Sherrington-Kirkpatrick (SK) spin-glass model with Gaussian couplings. While the ground states of SK spin-glass...
Glasses - the unknown known Filmmaterial (2008)
Aufzeichnung der Veranstaltung im Auditorium Maximum der ETH Zürich, Montag, 5. Mai 2008
Behavior of Ising Spin Glasses in a Magnetic Field (2007)
Jorg, Thomas, Katzgraber, Helmut G., Krzakala, Florent
We study the existence of a spin-glass phase in a field using Monte Carlo simulations performed along a nontrivial path in the field--temperature plane that must cross any putative de...
Local field distributions in spin glasses (2007)
Boettcher, Stefan, Katzgraber, Helmut G., Sherrington, David
Numerical results for the local field distributions of a family of Ising spin-glass models are presented. In particular, the Edwards-Anderson model in dimensions two, three, and four is considered,...
Spin glasses and algorithm benchmarks: A one-dimensional view (2007)
Spin glasses are paradigmatic models that deliver concepts relevant for a variety of systems. However, rigorous analytical results are difficult to obtain for spin-glass models, in particular for...
Albuquerque, A. Fabricio, Katzgraber, Helmut G., Troyer, Matthias, Blatter, Gianni
We use a nonperturbative extended contractor renormalization (ENCORE) method for engineering quantum devices for the implementation of topologically protected quantum bits described by an effective...
Gils, Charlotte, Katzgraber, Helmut G., Troyer, Matthias
We study numerically a monodisperse model of interacting classical particles predicted to exhibit a static liquid-glass transition. Using a dynamical Monte Carlo method we show that the model does...
Finite versus zero-temperature hysteretic behavior of spin glasses: Experiment and theory (2007)
Katzgraber, Helmut G., Herisson, D., Oesth, M., Nordblad, Per, Ito, Atsuko, Katori, Hiroko Aruga
We present experimental results attempting to fingerprint nonanalyticities in the magnetization curves of spin glasses found by Katzgraber et al. [Phys. Rev. Lett. 89, 257202 (2002)] via...
Katzgraber, Helmut G., Wuertz, D., Blatter, G.
We numerically compute the helicity modulus of the three-dimensional gauge glass by Monte Carlo simulations. Because the average free energy is independent of a twist angle, it is expected that the...
Effective critical behavior of the two-dimensional Ising spin glass with bimodal interactions (2006)
Katzgraber, Helmut G., Lee, Lik Wee, Campbell, I. A.
Monte Carlo data of the two-dimensional Ising spin glass with bimodal interactions are presented with the aim of understanding the low-temperature physics of the model. An analysis of the specific...
Simulations of ultracold bosonic atoms in optical lattices with anharmonic traps (2006)
Gygi, Olivier, Katzgraber, Helmut G., Troyer, Matthias, Wessel, Stefan, Batrouni, G. George
We report results of quantum Monte Carlo simulations in the canonical and the grand-canonical ensemble of the two- and three-dimensional Bose-Hubbard model with quadratic and quartic confining...
Temperature and Disorder Chaos in Three-Dimensional Ising Spin Glasses (2006)
Katzgraber, Helmut G., Krzakala, Florent
We study the effects of small temperature as well as disorder perturbations on the equilibrium state of three-dimensional Ising spin glasses via an alternate scaling ansatz. By using Monte Carlo...
Critical behavior of the three- and ten-state short-range Potts glass: A Monte Carlo study (2006)
Lee, L. W., Katzgraber, Helmut G., Young, A. P.
We study the critical behavior of the short-range p-state Potts spin glass in three and four dimensions using Monte Carlo simulations. In three dimensions, for p = 3, a finite-size scaling analysis...
Simulations of ultracold bosonic atoms in optical lattices with anharmonic traps (2006)
Gygi, Olivier, Katzgraber, Helmut G., Troyer, Matthias, Wessel, Stefan, Batrouni, G. George
We report results of quantum Monte Carlo simulations in the canonical and the grand-canonical ensemble of the two- and three-dimensional Bose-Hubbard model with quadratic and quartic confining...
Koerner, Mathias, Katzgraber, Helmut G., Hartmann, Alexander K.
We propose a simple and general procedure based on a recently introduced approach that uses an importance-sampling Monte Carlo algorithm in the disorder to probe to high precision the tails of...
Universality in three-dimensional Ising spin glasses: A Monte Carlo study (2006)
Katzgraber, Helmut G., Koerner, Mathias, Young, A. P.
We study universality in three-dimensional Ising spin glasses by large-scale Monte Carlo simulations of the Edwards-Anderson Ising spin glass for several choices of bond distributions, with...
Feedback-optimized parallel tempering Monte Carlo (2006)
Katzgraber, Helmut G., Trebst, Simon, Huse, David A., Troyer, Matthias
We introduce an algorithm to systematically improve the efficiency of parallel tempering Monte Carlo simulations by optimizing the simulated temperature set. Our approach is closely related to a...
Simulations of ultracold bosonic atoms in optical lattices with anharmonic traps (2006)
Gygi, Olivier, Katzgraber, Helmut G., Troyer, Matthias, Wessel, Stefan, Batrouni, G. George
We report results of quantum Monte Carlo simulations in the canonical and the grand-canonical ensemble of the two- and three-dimensional Bose-Hubbard model with quadratic and quartic confining...
Simulations of ultracold bosonic atoms in optical lattices with anharmonic traps (2006)
Gygi, Olivier, Katzgraber, Helmut G., Troyer, Matthias, Wessel, Stefan, Batrouni, G. George
We report results of quantum Monte Carlo simulations in the canonical and the grand-canonical ensemble of the two- and three-dimensional Bose-Hubbard model with quadratic and quartic confining...
Katzgraber, Helmut G., Lee, L. W., Campbell, I. A.
A detailed analysis of Monte Carlo data on the two-dimensional Ising spin glass with bimodal interactions shows that the free energy of the model has a nontrivial scaling. In particular, we show by...
Ramping fermions in optical lattices across a Feshbach resonance (2005)
Katzgraber, Helmut G., Esposito, Aniello, Troyer, Matthias
We study the properties of ultracold Fermi gases in a three-dimensional optical lattice when crossing a Feshbach resonance. By using a zero-temperature formalism, we show that three-body processes...
Hysteretic memory effects in disordered magnets (2005)
Katzgraber, Helmut G., Zimanyi, Gergely T.
We study the return point as well as the complementary point memory effects numerically with paradigmatic models for random magnets and show that already simple systems with Ising spin symmetry can...
Precise finite-sample quantiles of the Jarque-Bera adjusted Lagrange multiplier test (2005)
Wuertz, Diethelm, Katzgraber, Helmut G.
It is well known that the finite-sample null distribution of the Jarque-Bera Lagrange Multiplier (LM) test for normality and its adjusted version (ALM) introduced by Urzua differ considerably from...
Overcoming system-size limitations in spin glasses (2005)
Katzgraber, Helmut G., Koerner, Mathias, Liers, Frauke, Hartmann, A. K.
In order to overcome the limitations of small system sizes in spin-glass simulations, we investigate the one-dimensional Ising spin chain with power-law interactions. The model has the advantage over...
Probing the Almeida-Thouless line away from the mean-field model (2005)
Katzgraber, Helmut G., Young, A. P.
Results of Monte Carlo simulations of the one-dimensional long-range Ising spin glass with power-law interactions in the presence of a (random) field are presented. By tuning the exponent of the...
Universality-class dependence of energy distributions in spin glasses (2005)
Katzgraber, Helmut G., Koerner, Mathias, Liers, Frauke, Juenger, Michael, Hartmann, A. K.
We study the probability distribution function of the ground-state energies of the disordered one-dimensional Ising spin chain with power-law interactions using a combination of parallel tempering...
Dynamical scaling in Ising and vector spin glasses (2005)
Katzgraber, Helmut G., Campbell, I. A.
We have studied numerically the dynamics of spin glasses with Ising and XY symmetry (gauge glass) in space dimensions 2, 3, and 4. The nonequilibrium spin-glass susceptibility and the nonequilibrium...
Correlation length of the two-dimensional Ising spin glass with bimodal interactions (2004)
Katzgraber, Helmut G., Lee, L. W.
We study the correlation length of the two-dimensional Edwards-Anderson Ising spin glass with bimodal interactions using a combination of parallel tempering Monte Carlo and a rejection-free cluster...
Absence of an Almeida-Thouless line in Three-Dimensional Spin Glasses (2004)
Young, A. P., Katzgraber, Helmut G.
We present results of Monte Carlo simulations of the three-dimensional Edwards-Anderson Ising spin glass in the presence of a (random) field. A finite-size scaling analysis of the correlation length...
Energy size effects of two-dimensional Ising spin glasses (2004)
Campbell, I. A., Hartmann, A. K., Katzgraber, Helmut G.
We analyze exact ground-state energies of two-dimensional Ising spin glasses with either Gaussian or bimodal nearest-neighbor interactions for large system sizes and for three types of boundary...
Correlation Length of the Two-Dimensional Ising Spin Glass with Gaussian Interactions (2004)
Katzgraber, Helmut G., Lee, L. W., Young, A. P.
We study the correlation length of the two-dimensional Ising spin glass with a Gaussian distribution of interactions, using an efficient Monte Carlo algorithm proposed by Houdayer, that allows larger...
Critical properties of the three- and four-dimensional gauge glass (2003)
Katzgraber, Helmut G., Campbell, I. A.
The gauge glass in dimensions 3 and 4 is studied using a variety of numerical methods, in order to obtain accurate and reliable values for the critical parameters. Detailed comparisons are made of...
Size dependence of the internal energy in Ising and vector spin glasses (2003)
Katzgraber, Helmut G., Campbell, I. A.
We study numerically the scaling correction to the internal energy per spin as a function of system size and temperature in a variety of Ising and vector spin glasses. From a standard scaling...
Katzgraber, Helmut G., Young, A. P.
Results are presented for the geometry of low-energy excitations in the one-dimensional Ising spin chain with power-law interactions, in which the model parameters are chosen to yield a finite...
Fingerprinting Hysteresis (2003)
Katzgraber, Helmut G., Friedman, Gary, Zimanyi, G. T.
We test the predictive power of first-oder reversal curve (FORC) diagrams using simulations of random magnets. In particular, we compute a histogram of the switching fields of the underlying...
On the existence of a finite-temperature transition in the two-dimensional gauge glass (2003)
Results from Monte Carlo simulations of the two-dimensional gauge glass supporting a zero-temperature transition are presented. A finite-size scaling analysis of the correlation length shows that the...
Numerical studies of the 2 and 3D gauge glass at low temperature (2003)
We report results from Monte Carlo simulations of the two- and three-dimensional gauge glass at low temperature using parallel tempering Monte Carlo. In two dimensions, we find strong evidence for a...
International Journal of Modern Physics C (2002)
J. J. Moreno, Helmut G. Katzgraber, Alexander K. Hartmann
this paper. For easy problems one can apply exact algorithms to study large systems. But for hard problems no fast algorithms are available. Thus, very often heuristics and approximation methods are...
Numerical studies of the two- and three-dimensional gauge glass at low temperature (2002)
Katzgraber, Helmut G., Young, A. P.
We present results from Monte Carlo simulations of the two- and three-dimensional gauge glass at low temperature using the parallel tempering Monte Carlo method. Our results in two dimensions...
Monte Carlo Simulations of Vector Spin Glasses at Low Temperatures (2002)
In this paper I report results for simulations of the three-dimensional gauge glass and the four-dimensional XY spin glass using the parallel tempering Monte Carlo method at low temperatures for...
Katzgraber, Helmut G., Young, A. P.
We present results of Monte Carlo simulations, using parallel tempering, on the three- and four-dimensional Edwards-Anderson Ising spin glass with Gaussian couplings at low temperatures with free...
Monte Carlo simulations of the four-dimensional XY spin glass at low temperatures (2001)
Katzgraber, Helmut G., Young, A. P.
We report results for simulations of the four-dimensional XY spin glass using the parallel tempering Monte Carlo method at low temperatures for moderate sizes. Our results are qualitatively...
Nature of the Spin-glass State in the Three-dimensional Gauge Glass (2001)
Katzgraber, Helmut G., Young, A. P.
We present results from simulations of the gauge glass model in three dimensions using the parallel tempering Monte Carlo technique. Critical fluctuations should not affect the data since we...
Nature of the spin-glass state as seen from low-temperature Monte Carlo simulations / (2001)
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Monte Carlo Simulations of Spin Glasses at Low Temperatures (2000)
Katzgraber, Helmut G., Palassini, Matteo, Young, A. P.
We report the results of Monte Carlo simulations on several spin glass models at low temperatures. By using the parallel tempering (Exchange Monte Carlo) technique we are able to equilibrate down to...