56,808 research outputs found
Full electromagnetic Green's dyadic of spherically symmetric open optical systems and elimination of static modes from the resonant-state expansion
A general analytic form of the full 6 × 6 dyadic Green’s function of a spherically symmetric open optical system is presented, with an explicit solution provided for a homogeneous sphere in vacuum. Different spectral representations of the Green’s function are derived using the MittagLeffler theorem, and their convergence to the exact solution is analyzed, allowing us to select optimal representations. Based on them, more efficient versions of the resonant-state expansion (RSE) are formulated, with a particular focus on the static mode contribution, including versions of the RSE with a complete elimination of static modes. These general versions of the RSE, applicable to nonspherical optical systems, are verified and illustrated on exactly solvable examples of a dielectric sphere in vacuum with perturbations of its size and refractive index, demonstrating the same level of convergence to the exact solution for both transverse electric and transverse magnetic polarizations
More on Massive 3D Gravity
We explore the space of static solutions of the recently discovered
three-dimensional `New Massive Gravity' (NMG), allowing for either sign of the
Einstein-Hilbert term and a cosmological term parametrized by a dimensionless
constant . For we find black hole solutions asymptotic
(but not isometric) to the unique (anti) de Sitter vacuum, including extremal
black holes that interpolate between this vacuum and (a)dS. We
also investigate unitarity of linearized NMG in (a)dS vacua. We find unitary
theories for some dS vacua, but (bulk) unitarity in adS implies negative
central charge of the dual CFT, except for where the central charge
vanishes and the bulk gravitons are replaced by `massive photons'. A similar
phenomenon is found in the massless limit of NMG, for which the linearized
equations become equivalent to Maxwell's equations.Comment: 25 pages, 4 figures; v2: minor improvements and extensions,
references added; v3: version to appear in PR
Boundary Conditions and Quasilocal Energy in the Canonical Formulation of All 1+1 Models of Gravity
Within a first-order framework, we comprehensively examine the role played by
boundary conditions in the canonical formulation of a completely general
two-dimensional gravity model. Our analysis particularly elucidates the
perennial themes of mass and energy. The gravity models for which our arguments
are valid include theories with dynamical torsion and so-called generalized
dilaton theories (GDTs). Our analysis of the canonical action principle (i)
provides a rigorous correspondence between the most general first-order
two-dimensional Einstein-Cartan model (ECM) and GDT and (ii) allows us to
extract in a virtually simultaneous manner the ``true degrees of freedom'' for
both ECMs and GDTs. For all such models, the existence of an absolutely
conserved (in vacuo) quantity C is a generic feature, with (minus) C
corresponding to the black-hole mass parameter in the important special cases
of spherically symmetric four-dimensional general relativity and standard
two-dimensional dilaton gravity. The mass C also includes (minimally coupled)
matter into a ``universal mass function.'' We place particular emphasis on the
(quite general) class of models within GDT possessing a Minkowski-like
groundstate solution (allowing comparison between and the
Arnowitt-Deser-Misner mass for such models).Comment: REVTeX, 41 pages, 2 Postscript figures, 10 macro
Polyakov Loop Dynamics in the Center Symmetric Phase
A study of the center symmetric phase of SU(2) Yang Mills theory is
presented. Realization of the center symmetry is shown to result from
non-perturbative gauge fixing. Dictated by the center symmetry, this phase
exhibits already at the perturbative level confinement like properties. The
analysis is performed by investigating the dynamics of the Polyakov loops. The
ultralocality of these degrees of freedom implies significant changes in the
vacuum structure of the theory. General properties of the confined phase and of
the transition to the deconfined phase are discussed. Perturbation theory built
upon the vacuum of ultralocal Polyakov loops is presented and used to
calculate, via the Polyakov loop correlator, the static quark-antiquark
potential.Comment: 45 pages, LaTeX, 8 figure
Birkhoff's Theorem for Quasi-Metric Gravity
Working within the quasi-metric framework (QMF), it is examined if the
gravitational field exterior to an isolated, spherically symmetric body is
necessarily metrically static; or equivalently, whether or not Birkhoff's
theorem holds for quasi-metric gravity. It is found that it does; however the
proof is somewhat different from the general-relativistic case.Comment: 9 page
Entanglement negativity, Holography and Black holes
We investigate the application of our recent holographic entanglement
negativity conjecture for higher dimensional conformal field theories to
specific examples which serve as crucial consistency checks. In this context we
compute the holographic entanglement negativity for bipartite pure and finite
temperature mixed state configurations in -dimensional conformal field
theories dual to bulk pure geometry and -Schwarzschild
black holes respectively. It is observed that the holographic entanglement
negativity characterizes the distillable entanglement for the finite
temperature mixed states through the elimination of the thermal contributions.
Significantly our examples correctly reproduce universal features of the
entanglement negativity for corresponding two dimensional conformal field
theories, in higher dimensions.Comment: 32 pages, 3 figures, minor modification
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