scholarly journals DMRG investigation of constrained models: from quantum dimer and quantum loop ladders to hard-boson and Fibonacci anyon chains

2019 ◽  
Vol 6 (3) ◽  
Author(s):  
Natalia Chepiga ◽  
Frédéric Mila
Keyword(s):  
Model Building ◽  
Fibonacci Number ◽  
Complete Analysis ◽  
Loop Model ◽  
Boundary Field ◽  
Conformal Field ◽  
Density Matrix Renormalization ◽  
Early Results ◽  
Boson Model ◽  
Constrained Models

Motivated by the presence of Ising transitions that take place entirely in the singlet sector of frustrated spin-1/2 ladders and spin-1 chains, we study two types of effective dimer models on ladders, a quantum dimer model and a quantum loop model. Building on the constraints imposed on the dimers, we develop a Density Matrix Renormalization Group algorithm that takes full advantage of the relatively small Hilbert space that only grows as Fibonacci number. We further show that both models can be mapped rigorously onto a hard-boson model first studied by Fendley, Sengupta and Sachdev [Phys. Rev. B 69, 075106 (2004)], and combining early results with recent results obtained with the present algorithm on this hard-boson model, we discuss the full phase diagram of these quantum dimer and quantum loop models, with special emphasis on the phase transitions. In particular, using conformal field theory, we fully characterize the Ising transition and the tricritical Ising end point, with a complete analysis of the boundary-field correspondence for the tricritical Ising point including partially polarized edges. Finally, we show that the Fibonacci anyon chain is exactly equivalent to special critical points of these models.

CONFORMAL FIELD THEORIES ON SURFACES WITH BOUNDARIES AND CROSSCAPS

1989 ◽  
Vol 04 (02) ◽  
pp. 161-168 ◽  
Author(s):  
TETSUYA ONOGI ◽  
NOBUYUKI ISHIBASHI
Keyword(s):  
Crucial Role ◽  
Model Building ◽  
Open String ◽  
Theory Model ◽  
Field Theories ◽  
Partition Functions ◽  
Conformal Field Theories ◽  
Modular Invariant ◽  
Conformal Field ◽  
Loop Channel

We classify the possible operator contents of the minimal conformal field theories when boundaries and crosscaps are present by imposing loop channel-tree channel duality conditions. These are the open string analogues of modular invariant partition functions, which play a crucial role in string theory model building.

scholarly journals Ground state entanglement in quantum spin chains

2004 ◽  
Vol 4 (1) ◽  
pp. 48-92 ◽  
Author(s):  
J.I. Latorre ◽  
E. Rico ◽  
G. Vidal
Keyword(s):  
Renormalization Group ◽  
Ground State ◽  
Quantum Phase Transitions ◽  
Conformal Symmetry ◽  
Mass Scale ◽  
Quantum Spin ◽  
Density Matrix Renormalization Group ◽  
Quantum Spin Chains ◽  
Conformal Field ◽  
Density Matrix Renormalization

A microscopic calculation of ground state entanglement for the XY and Heisenberg models shows the emergence of universal scaling behavior at quantum phase transitions. Entanglement is thus controlled by conformal symmetry. Away from the critical point, entanglement gets saturated by a mass scale. Results borrowed from conformal field theory imply irreversibility of entanglement loss along renormalization group trajectories. Entanglement does not saturate in higher dimensions which appears to limit the success of the density matrix renormalization group technique. A possible connection between majorization and renormalization group irreversibility emerges from our numerical analysis.

A New Wave of Illumination -ISS OBC Acquisition in the Columbus Basin

2014 ◽  
Author(s):  
T.. Rampersad ◽  
A.. Cegna ◽  
C Steiner ◽  
J.. Kommedal
Keyword(s):  
Model Building ◽  
Waveform Inversion ◽  
Velocity Model ◽  
Shallow Gas ◽  
Velocity Model Building ◽  
Spot Detection ◽  
Early Results ◽  
Seismic Acquisition ◽  
Streamer Data ◽  
Spatial Positioning

Abstract The Independent Simultaneous Source (ISS) seismic acquisition in the southern Columbus Basin conducted by WesternGeco for BPTT is in the early stages of seismic processing. Early results are already revealing improved imaging and structural interpretations. Improvements in imaging and depth conversion are compelling, largely the result of full azimuths, longer azimuths, higher fold, lower frequency content and P/Z recording. Because of these factors the resultant OBC data leads to improved velocity model building utilizing BP's Full Waveform Inversion, FWI, techniques. In a field wide comparison done in the southern part of the basin the OBC image provided marked increases in the following over the heritage streamer data; Fault clarity, where reflector terminations and linkages are much clearer.Reflector continuity, especially in the deeper (greater than 12,000 ft. depths). This improvement seen throughout the dataset is most noticeable below shallow gas accumulations and in areas next to platforms previously only covered by lower fold data. Seismic sequences are also now more interpretable.Flat-spot detection where previous identification was unknown.Early results also point to improved spatial positioning of reflectors under shallow gas accumulations and, in the depth migrated volumes, the removal of the sag due to incorrect velocity fields. This paper illustrates comparisons in the Columbus Basin between the new OBC data and heritage streamer data in support of the above claims of improved image and depth positioning.

Statistical Field Theory

2020 ◽  
Author(s):  
Giuseppe Mussardo
Keyword(s):  
Field Theory ◽  
Form Factors ◽  
Theoretical Physics ◽  
Quantum Field Theories ◽  
Boundary Field ◽  
Conformal Field ◽  
Statistical Field ◽  
Statistical Field Theory ◽  
Substantial Progress ◽  
Theoretical Physicist

This book is an introduction to statistical field theory, which is an important subject within theoretical physics and a field that has seen substantial progress in recent years. The book covers fundamental topics in great detail and includes areas like conformal field theory, quantum integrability, S-matrices, braiding groups, Bethe ansatz, renormalization groups, Majorana fermions, form factors, the truncated conformal space approach and boundary field theory. It also provides an introduction to lattice statistical models. Many topics are discussed at a fairly advanced level but via a pedagogical approach. In particular, the book presents in a clear way non-perturbative methods of quantum field theories that have become decisive tools in many different areas of statistical and condensed matter physics, and which are currently an essential foundation of the working knowledge of a modern theoretical physicist.

scholarly journals Bounds on Regge growth of flat space scattering from bounds on chaos

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Deeksha Chandorkar ◽  
Subham Dutta Chowdhury ◽  
Suman Kundu ◽  
Shiraz Minwalla
Keyword(s):  
Field Theory ◽  
Conformal Field Theory ◽  
Flat Space ◽  
Gauge Fields ◽  
Point Singularity ◽  
Boundary Field ◽  
Conformal Field ◽  
S Matrix ◽  
Regge Limit ◽  
Conserved Currents

Abstract We study four-point functions of scalars, conserved currents, and stress tensors in a conformal field theory, generated by a local contact term in the bulk dual description, in two different causal configurations. The first of these is the standard Regge configuration in which the chaos bound applies. The second is the ‘causally scattering configuration’ in which the correlator develops a bulk point singularity. We find an expression for the coefficient of the bulk point singularity in terms of the bulk S matrix of the bulk dual metric, gauge fields and scalars, and use it to determine the Regge scaling of the correlator on the causally scattering sheet in terms of the Regge growth of this S matrix. We then demonstrate that the Regge scaling on this sheet is governed by the same power as in the standard Regge configuration, and so is constrained by the chaos bound, which turns out to be violated unless the bulk flat space S matrix grows no faster than s2 in the Regge limit. It follows that in the context of the AdS/CFT correspondence, the chaos bound applied to the boundary field theory implies that the S matrices of the dual bulk scalars, gauge fields, and gravitons obey the Classical Regge Growth (CRG) conjecture.

scholarly journals Entanglement spreading after local fermionic excitations in the XXZ chain

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Matthias Gruber ◽  
Viktor Eisler
Keyword(s):  
Spectral Weight ◽  
Majorana Fermion ◽  
Density Matrix Renormalization Group ◽  
Initial State ◽  
Conformal Field ◽  
Multiplicative Factor ◽  
Density Matrix Renormalization ◽  
Liquid Theory ◽  
Xxz Chain ◽  
Theory Framework

We study the spreading of entanglement produced by the time evolution of a local fermionic excitation created above the ground state of the XXZ chain. The resulting entropy profiles are investigated via density-matrix renormalization group calculations, and compared to a quasiparticle ansatz. In particular, we assume that the entanglement is dominantly carried by spinon excitations traveling at different velocities, and the entropy profile is reproduced by a probabilistic expression involving the density fraction of the spinons reaching the subsystem. The ansatz works well in the gapless phase for moderate values of the XXZ anisotropy, eventually deteriorating as other types of quasiparticle excitations gain spectral weight. Furthermore, if the initial state is excited by a local Majorana fermion, we observe a nontrivial rescaling of the entropy profiles. This effect is further investigated in a conformal field theory framework, carrying out calculations for the Luttinger liquid theory. Finally, we also consider excitations creating an antiferromagnetic domain wall in the gapped phase of the chain, and find again a modified quasiparticle ansatz with a multiplicative factor.

scholarly journals Modular Hamiltonians in flat holography and (W)AdS/WCFT

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Luis Apolo ◽  
Hongliang Jiang ◽  
Wei Song ◽  
Yuan Zhong
Keyword(s):  
Quantum Gravity ◽  
Entanglement Entropy ◽  
Three Dimensional ◽  
Neumann Boundary ◽  
Field Theories ◽  
Covariant Formulation ◽  
Boundary Field ◽  
Conformal Field ◽  
Holographic Duals ◽  
Holographic Description

Abstract We study several aspects of holographic entanglement in two models known as flat3/BMSFT and (W)AdS3/WCFT. These are two examples of holography beyond AdS/CFT where the boundary field theories are not Lorentz invariant but still feature an infinite set of local symmetries. In the first example, BMS-invariant field theories (BMSFTs) are conjectured to provide a holographic description of quantum gravity in asymptotically flat three-dimensional spacetimes; while in the second example, warped conformal field theories (WCFTs) are proposed to describe quantum gravity in warped AdS3 or AdS3 backgrounds with Dirichlet-Neumann boundary conditions. In particular, we derive the modular Hamiltonian for single intervals in both BMSFTs and WCFTs and find the holographic duals in the bulk using the covariant formulation of gravitational charges. We also extend the first law of entanglement entropy to these models of non-AdS holography and discuss the bound on “modular chaos” introduced recently in the context of the AdS/CFT correspondence.

Clinical Update: Assessing Maximum Medical Improvement in Carpal Tunnel Syndrome

2003 ◽  
Vol 8 (4) ◽  
pp. 4-5
Author(s):  
Christopher R. Brigham ◽  
James B. Talmage
Keyword(s):  
Carpal Tunnel Syndrome ◽  
Carpal Tunnel ◽  
Proper Time ◽  
Carpal Tunnel Release ◽  
Hand Function ◽  
Factors Affecting ◽  
Early Results ◽  
Medical Evaluation ◽  
Nerve Recovery ◽  
Tunnel Syndrome

Abstract Permanent impairment cannot be assessed until the patient is at maximum medical improvement (MMI), but the proper time to test following carpal tunnel release often is not clear. The AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) states: “Factors affecting nerve recovery in compression lesions include nerve fiber pathology, level of injury, duration of injury, and status of end organs,” but age is not prognostic. The AMA Guides clarifies: “High axonotmesis lesions may take 1 to 2 years for maximum recovery, whereas even lesions at the wrist may take 6 to 9 months for maximal recovery of nerve function.” The authors review 3 studies that followed patients’ long-term recovery of hand function after open carpal tunnel release surgery and found that estimates of MMI ranged from 25 weeks to 24 months (for “significant improvement”) to 18 to 24 months. The authors suggest that if the early results of surgery suggest a patient's improvement in the activities of daily living (ADL) and an examination shows few or no symptoms, the result can be assessed early. If major symptoms and ADL problems persist, the examiner should wait at least 6 to 12 months, until symptoms appear to stop improving. A patient with carpal tunnel syndrome who declines a release can be rated for impairment, and, as appropriate, the physician may wish to make a written note of this in the medical evaluation report.

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