111 research outputs found
High-Resolution Scalar Quantization with RĂ©nyi Entropy Constraint
We consider optimal scalar quantization with th power distortion and constrained R\'enyi entropy of order . For sources with absolutely continuous distributions the high rate asymptotics of the quantizer distortion has long been known for (fixed-rate quantization) and (entropy-constrained quantization). These results have recently been extended to quantization with R\'enyi entropy constraint of order . Here we consider the more challenging case and for a large class of absolutely continuous source distributions we determine the sharp asymptotics of the optimal quantization distortion. The achievability proof is based on finding (asymptotically) optimal quantizers via the companding approach, and is thus constructive
Information Extraction Under Privacy Constraints
A privacy-constrained information extraction problem is considered where for
a pair of correlated discrete random variables governed by a given
joint distribution, an agent observes and wants to convey to a potentially
public user as much information about as possible without compromising the
amount of information revealed about . To this end, the so-called {\em
rate-privacy function} is introduced to quantify the maximal amount of
information (measured in terms of mutual information) that can be extracted
from under a privacy constraint between and the extracted information,
where privacy is measured using either mutual information or maximal
correlation. Properties of the rate-privacy function are analyzed and
information-theoretic and estimation-theoretic interpretations of it are
presented for both the mutual information and maximal correlation privacy
measures. It is also shown that the rate-privacy function admits a closed-form
expression for a large family of joint distributions of . Finally, the
rate-privacy function under the mutual information privacy measure is
considered for the case where has a joint probability density function
by studying the problem where the extracted information is a uniform
quantization of corrupted by additive Gaussian noise. The asymptotic
behavior of the rate-privacy function is studied as the quantization resolution
grows without bound and it is observed that not all of the properties of the
rate-privacy function carry over from the discrete to the continuous case.Comment: 55 pages, 6 figures. Improved the organization and added detailed
literature revie
Progress in Group Field Theory and Related Quantum Gravity Formalisms
Following the fundamental insights from quantum mechanics and general relativity, geometry itself should have a quantum description; the search for a complete understanding of this description is what drives the field of quantum gravity. Group field theory is an ambitious framework in which theories of quantum geometry are formulated, incorporating successful ideas from the fields of matrix models, ten-sor models, spin foam models and loop quantum gravity, as well as from the broader areas of quantum field theory and mathematical physics. This special issue collects recent work in group field theory and these related approaches, as well as other neighbouring fields (e.g., cosmology, quantum information and quantum foundations, statistical physics) to the extent that these are directly relevant to quantum gravity research
Holographic entanglement in group field theory
This work is meant as a review summary of a series of recent results concerning the derivation of a holographic entanglement entropy formula for generic open spin network states in the group field theory (GFT) approach to quantum gravity. The statistical group-field computation of the RĂ©nyi entropy for a bipartite network state for a simple interacting GFT is reviewed, within a recently proposed dictionary between group field theories and random tensor networks, and with an emphasis on the problem of a consistent characterisation of the entanglement entropy in the GFT second quantisation formalism
Radial coordinates for defect CFTs
We study the two-point function of local operators in the presence of a
defect in a generic conformal field theory. We define two pairs of cross
ratios, which are convenient in the analysis of the OPE in the bulk and defect
channel respectively. The new coordinates have a simple geometric
interpretation, which can be exploited to efficiently compute conformal blocks
in a power expansion. We illustrate this fact in the case of scalar external
operators. We also elucidate the convergence properties of the bulk and defect
OPE decompositions of the two-point function. In particular, we remark that the
expansion of the two-point function in powers of the new cross ratios converges
everywhere, a property not shared by the cross ratios customarily used in
defect CFT. We comment on the crucial relevance of this fact for the numerical
bootstrap.Comment: Matches journal version; the attached mathematica file (Bulk CB.nb +
rec.txt) computes the conformal blocks in the bulk channe
Cosmological Inflation, Dark Matter and Dark Energy
Various cosmological observations support not only cosmological inflation in the early universe, which is also known as exponential cosmic expansion, but also that the expansion of the late-time universe is accelerating. To explain this phenomenon, the existence of dark energy is proposed. In addition, according to the rotation curve of galaxies, the existence of dark matter, which does not shine, is also suggested. If primordial gravitational waves are detected in the future, the mechanism for realizing inflation can be revealed. Moreover, there exist two main candidates for dark matter. The first is a new particle, the existence of which is predicted in particle physics. The second is an astrophysical object which is not found by electromagnetic waves. Furthermore, there are two representative approaches to account for the accelerated expansion of the current universe. One is to assume the unknown dark energy in general relativity. The other is to extend the gravity theory to large scales. Investigation of the origins of inflation, dark matter, and dark energy is one of the most fundamental problems in modern physics and cosmology. The purpose of this book is to explore the physics and cosmology of inflation, dark matter, and dark energy
Transform coding with backwards adaptive updates
The KarhunenâLoĂšve transform (KLT) is optimal for trans- form coding of a Gaussian source. This is established for all scale-invariant quantizers, generalizing previous results. A backward adaptive technique for combating the data dependence of the KLT is proposed and analyzed. When the adapted transform converges to a KLT, the scheme is universal among transform coders. A variety of convergence results are proven
Quantum Hypothesis Testing and Non-Equilibrium Statistical Mechanics
We extend the mathematical theory of quantum hypothesis testing to the
general -algebraic setting and explore its relation with recent
developments in non-equilibrium quantum statistical mechanics. In particular,
we relate the large deviation principle for the full counting statistics of
entropy flow to quantum hypothesis testing of the arrow of time.Comment: 60 page
Eigenvalue Distributions of Reduced Density Matrices
Given a random quantum state of multiple distinguishable or indistinguishable
particles, we provide an effective method, rooted in symplectic geometry, to
compute the joint probability distribution of the eigenvalues of its one-body
reduced density matrices. As a corollary, by taking the distribution's support,
which is a convex moment polytope, we recover a complete solution to the
one-body quantum marginal problem. We obtain the probability distribution by
reducing to the corresponding distribution of diagonal entries (i.e., to the
quantitative version of a classical marginal problem), which is then determined
algorithmically. This reduction applies more generally to symplectic geometry,
relating invariant measures for the coadjoint action of a compact Lie group to
their projections onto a Cartan subalgebra, and can also be quantized to
provide an efficient algorithm for computing bounded height Kronecker and
plethysm coefficients.Comment: 51 pages, 7 figure
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