MEMORIAL TRIBUTE TO MANFRED L. RISTIG (1935–2011)

2013 ◽  
Vol 27 (29) ◽  
pp. 1347003
Author(s):  
JOHN W. CLARK
Keyword(s):  
Matrix Theory ◽  
Microscopic Theory ◽  
Quantum Fluids ◽  
Strong Interactions ◽  
Many Body ◽  
Exchange Effects ◽  
Nuclear Systems ◽  
Hypernetted Chain ◽  
Many Body Systems ◽  
Density Matrix Theory

Manfred Ristig was a leading contributor to the advancement of microscopic theory of strongly interacting quantum many-body systems for over four decades. This retrospective on his life and scientific career pays tribute to his pivotal role in the development of correlated wavefunction approaches to quantitative ab initio description of quantum fluids, nuclear systems and condensed matter more generally. Highlights include his contributions to the formulation of Fermi hypernetted chain theory and correlated density matrix theory. Special attention is given to Ristig's seminal work of recent years, which has yielded rich insights into the interplay of exchange effects (arising from quantum statistics) and the strong interactions between constituent bosons or fermions.

Spin-Polarized Quantum Fluids and Solids

MRS Bulletin ◽  
1993 ◽  
Vol 18 (8) ◽  
pp. 38-43
Author(s):  
Kevin S. Bedell ◽  
Isaac F. Silvera ◽  
Neil S. Sullivan
Keyword(s):  
Magnetic Ordering ◽  
Quantum Fluids ◽  
Einstein Condensation ◽  
Many Body ◽  
Spin Polarized ◽  
Many Body Systems ◽  
The Rich ◽  
Bose Einstein ◽  
Physical Phenomena

The spin-polarized phases of the quantum fluids and solids, liquid 3He, solid 3He, and spin-aligned hydrogen have generated considerable excitement over the past fifteen years. The introduction of high magnetic fields (B ∼ 10–30 T) in conjunction with low temperatures (T ≲ 100 mK) has given rise to opportunities for exploring some of the new phases predicted for these materials. There is a broad range of physical phenomena that can be accessed in this regime of parameter space—unconventional superfluidity, unusual magnetic ordering, Bose-Einstein condensation and Kosterlitz-Thouless transitions, to name a few. This is most surprising since this plethora of complicated states of matter are present in some of the most uncomplicated materials. The rich variety of phases found in these materials are all examples of collective phenomena of quantum many-body systems, and they serve as prototypes for developing an understanding of magnetism and order/disorder processes in other systems, and for the design and characterization of new materials.

scholarly journals Landau–Zener Effect in Superfluid Nuclear Systems

2003 ◽  
Vol 18 (26) ◽  
pp. 1809-1817 ◽  
Author(s):  
M. Mirea
Keyword(s):  
Equations Of Motion ◽  
Deformation Energy ◽  
Cluster Decay ◽  
Many Body ◽  
Spectroscopic Factors ◽  
Nuclear Systems ◽  
Particle Level ◽  
Many Body Systems ◽  
Experimental Ratio ◽  
Good Agreement

The Landau–Zener effect is generalized for many-body systems with pairing residual interactions. The microscopic equations of motion are obtained and the 14C decay of 223Ra spectroscopic factors are deduced. An asymmetric nuclear shape parametrization given by two intersected spheres is used. The single particle level scheme is determined in the frame of the superasymmetric two-center shell model. The deformation energy is computed in the microscopic–macroscopic approximation. The penetrabilities are obtained within the WKB approximation. The fine structure of the cluster decay analyzed in the frame of this formalism gives a very good agreement with the experimental ratio of partial half-lives for transition to the first excited state and to the ground state.

Prospective Merger Between Car-Parrinello and Lattice Boltzmann Methods for Quantum Many-Body Simulations

2011 ◽  
Vol 9 (5) ◽  
pp. 1137-1151 ◽  
Author(s):  
Sauro Succi ◽  
Silvia Palpacelli
Keyword(s):  
Molecular Dynamics ◽  
Computational Efficiency ◽  
Lattice Boltzmann ◽  
Quantum Fluids ◽  
Ab Initio Molecular Dynamics ◽  
Many Body ◽  
Lattice Boltzmann Methods ◽  
Quantum Simulations ◽  
Speed Up ◽  
Many Body Systems

AbstractFormal analogies between the Car-Parrinello (CP) ab-initio molecular dynamics for quantum many-body systems, and the Lattice Boltzmann (LB) method for classical and quantum fluids, are pointed out. A theoretical scenario, whereby the quantum LB would be coupled to the CP framework to speed-up many-body quantum simulations, is also discussed, together with accompanying considerations on the computational efficiency of the prospective CP-LB scheme.

scholarly journals Spin-imbalance in a 2D Fermi-Hubbard system

Science ◽  
2017 ◽  
Vol 357 (6358) ◽  
pp. 1385-1388 ◽  
Author(s):  
Peter T. Brown ◽  
Debayan Mitra ◽  
Elmer Guardado-Sanchez ◽  
Peter Schauß ◽  
Stanimir S. Kondov ◽  
...  
Keyword(s):  
Hubbard Model ◽  
Metallic Phase ◽  
Strong Interactions ◽  
Temperature Phase ◽  
Strongly Correlated ◽  
Many Body ◽  
Open Questions ◽  
Antiferromagnetic Correlations ◽  
Strongly Correlated Fermions ◽  
Many Body Systems

The interplay of strong interactions and magnetic fields gives rise to unusual forms of superconductivity and magnetism in quantum many-body systems. Here, we present an experimental study of the two-dimensional Fermi-Hubbard model—a paradigm for strongly correlated fermions on a lattice—in the presence of a Zeeman field and varying doping. Using site-resolved measurements, we revealed anisotropic antiferromagnetic correlations, a precursor to long-range canted order. We observed nonmonotonic behavior of the local polarization with doping for strong interactions, which we attribute to the evolution from an antiferromagnetic insulator to a metallic phase. Our results pave the way to experimentally mapping the low-temperature phase diagram of the Fermi-Hubbard model as a function of both doping and spin polarization, for which many open questions remain.

Correlated density matrix theory of normal quantum fluids

1992 ◽  
Vol 218 (1) ◽  
pp. 160-196 ◽  
Author(s):  
G Senger ◽  
M.L Ristig ◽  
C.E Campbell ◽  
J.W Clark
Keyword(s):  
Density Matrix ◽  
Matrix Theory ◽  
Quantum Fluids ◽  
Density Matrix Theory

scholarly journals Random matrix theory of the isospectral twirling

2021 ◽  
Vol 10 (3) ◽  
Author(s):  
Salvatore Francesco Emanuele Oliviero ◽  
Lorenzo Leone ◽  
Francesco Caravelli ◽  
Alioscia Hamma
Keyword(s):  
Mutual Information ◽  
Random Matrix Theory ◽  
Random Matrix ◽  
Quantum Dynamics ◽  
Matrix Theory ◽  
Probability Distributions ◽  
Equilibrium States ◽  
Many Body ◽  
Many Body Systems ◽  
Integrable Dynamics

We present a systematic construction of probes into the dynamics of isospectral ensembles of Hamiltonians by the notion of Isospectral twirling, expanding the scopes and methods of ref. [1]. The relevant ensembles of Hamiltonians are those defined by salient spectral probability distributions. The Gaussian Unitary Ensembles (GUE) describes a class of quantum chaotic Hamiltonians, while spectra corresponding to the Poisson and Gaussian Diagonal Ensemble (GDE) describe non chaotic, integrable dynamics. We compute the Isospectral twirling of several classes of important quantities in the analysis of quantum many-body systems: Frame potentials, Loschmidt Echos, OTOCs, Entanglement, Tripartite mutual information, coherence, distance to equilibrium states, work in quantum batteries and extension to CP-maps. Moreover, we perform averages in these ensembles by random matrix theory and show how these quantities clearly separate chaotic quantum dynamics from non chaotic ones.

scholarly journals Spectral decoupling in many-body quantum chaos

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Jordan Cotler ◽  
Nicholas Hunter-Jones
Keyword(s):  
Random Matrix Theory ◽  
Random Matrix ◽  
Correlation Functions ◽  
Quantum Chaos ◽  
Matrix Theory ◽  
Energy Eigenvalue ◽  
Time Dependent ◽  
Late Time ◽  
Many Body ◽  
Many Body Systems

Abstract We argue that in a large class of disordered quantum many-body systems, the late time dynamics of time-dependent correlation functions is captured by random matrix theory, specifically the energy eigenvalue statistics of the corresponding ensemble of disordered Hamiltonians. We find that late time correlation functions approximately factorize into a time-dependent piece, which only depends on spectral statistics of the Hamiltonian ensemble, and a time-independent piece, which only depends on the data of the constituent operators of the correlation function. We call this phenomenon “spectral decoupling”, which signifies a dynamical onset of random matrix theory in correlation functions. A key diagnostic of spectral decoupling is k-invariance, which we refine and study in detail. Particular emphasis is placed on the role of symmetries, and connections between k-invariance, scrambling, and OTOCs. Disordered Pauli spin systems, as well as the SYK model and its variants, provide a rich source of disordered quantum many-body systems with varied symmetries, and we study k-invariance in these models with a combination of analytics and numerics.

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