843 research outputs found
Bound-State Variational Wave Equation For Fermion Systems In QED
We present a formulation of the Hamiltonian variational method for QED which
enables the derivation of relativistic few-fermion wave equation that can
account, at least in principle, for interactions to any order of the coupling
constant. We derive a relativistic two-fermion wave equation using this
approach. The interaction kernel of the equation is shown to be the generalized
invariant M-matrix including all orders of Feynman diagrams. The result is
obtained rigorously from the underlying QFT for arbitrary mass ratio of the two
fermions. Our approach is based on three key points: a reformulation of QED,
the variational method, and adiabatic hypothesis. As an application we
calculate the one-loop contribution of radiative corrections to the two-fermion
binding energy for singlet states with arbitrary principal quantum number ,
and . Our calculations are carried out in the explicitly covariant
Feynman gauge.Comment: 26 page
Nonsymmetric Gravitational Theory
A new version of nonsymmetric gravitational theory is presented. The field
equations are expanded about the Minkowski metric, giving in lowest order the
linear Einstein field equations and massive Proca field equations for the
antisymmetric field . An expansion about an arbitrary Einstein
background metric yields massive Proca field equations with couplings to only
physical modes. It follows that the new version of NGT is free of ghost poles,
tachyons and higher-order poles and there are no problems with asymptotic
boundary conditions. A static spherically symmetric solution of the field
equations in the short-range approximation is everywhere regular and does not
contain a black hole event horizon.Comment: 11 pages plain TeX. TeX macrofile included. Corrections in formula
Conditional probabilities in Ponzano-Regge minisuperspace
We examine the Hartle-Hawking no-boundary initial state for the Ponzano-Regge
formulation of gravity in three dimensions. We consider the behavior of
conditional probabilities and expectation values for geometrical quantities in
this initial state for a simple minisuperspace model consisting of a
two-parameter set of anisotropic geometries on a 2-sphere boundary. We find
dependence on the cutoff used in the construction of Ponzano-Regge amplitudes
for expectation values of edge lengths. However, these expectation values are
cutoff independent when computed in certain, but not all, conditional
probability distributions. Conditions that yield cutoff independent expectation
values are those that constrain the boundary geometry to a finite range of edge
lengths. We argue that such conditions have a correspondence to fixing a range
of local time, as classically associated with the area of a surface for
spatially closed cosmologies. Thus these results may hint at how classical
spacetime emerges from quantum amplitudes.Comment: 26 pages including 10 figures, some reorganization in the
presentation of results, expanded discussion of results in the context of 2+1
gravity in the Witten variables, 3 new reference
Resolving Curvature Singularities in Holomorphic Gravity
We formulate holomorphic theory of gravity and study how the holomorphy
symmetry alters the two most important singular solutions of general
relativity: black holes and cosmology. We show that typical observers (freely)
falling into a holomorphic black hole do not encounter a curvature singularity.
Likewise, typical observers do not experience Big Bang singularity. Unlike
Hermitian gravity \cite{MantzHermitianGravity}, Holomorphic gravity does not
respect the reciprocity symmetry and thus it is mainly a toy model for a
gravity theory formulated on complex space-times. Yet it is a model that
deserves a closer investigation since in many aspects it resembles Hermitian
gravity and yet calculations are simpler. We have indications that holomorphic
gravity reduces to the laws of general relativity correctly at large distance
scales.Comment: 14 pages, 7 figure
Quantum corrections to the entropy of charged rotating black holes
Hawking radiation from a black hole can be viewed as quantum tunneling of
particles through the event horizon. Using this approach we provide a general
framework for studying corrections to the entropy of black holes beyond
semiclassical approximations. Applying the properties of exact differentials
for three variables to the first law thermodynamics, we study charged rotating
black holes and explicitly work out the corrections to entropy and horizon area
for the Kerr-Newman and charged rotating BTZ black holes. It is shown that the
results for other geometries like the Schwarzschild, Reissner-Nordstr\"{o}m and
anti-de Sitter Schwarzschild spacetimes follow easily
Two-dimensional dS/CFT correspondence
We investigate de Sitter/conformal field theory (dS/CFT) correspondence in
two dimensions. We define the conserved mass of de Sitter spacetime and
formulate the correspondence along the lines of anti-de Sitter/conformal field
theory duality. Asymptotic symmetry group, mass, and central charge of de
Sitter spacetime are equal to those of anti-de Sitter spacetime. The entropy of
two-dimensional de Sitter spacetime is evaluated by applying Cardy formula. We
calculate the boundary correlators induced by the propagation of the dilaton in
two-dimensional de Sitter space. Although the dilaton is a tachyonic
perturbation in the bulk, boundary conformal correlators have positive
dimension.Comment: 18 pages, Latex fil
Nonholonomic Ricci Flows, Exact Solutions in Gravity, and Symmetric and Nonsymmetric Metrics
We provide a proof that nonholonomically constrained Ricci flows of (pseudo)
Riemannian metrics positively result into nonsymmetric metrics (as explicit
examples, we consider flows of some physically valuable exact solutions in
general relativity). There are constructed and analyzed three classes of
solutions of Ricci flow evolution equations defining nonholonomic deformations
of Taub NUT, Schwarzschild, solitonic and pp--wave symmetric metrics into
nonsymmetric ones.Comment: latex2e, 12pt, 40 pages, version 2 with minor modifications, to be
published in Int. J. Theor. Phy
Electromagnetic Polarization Effects due to Axion Photon Mixing
We investigate the effect of axions on the polarization of electromagnetic
waves as they propagate through astronomical distances. We analyze the change
in the dispersion of the electromagnetic wave due to its mixing with axions. We
find that this leads to a shift in polarization and turns out to be the
dominant effect for a wide range of frequencies. We analyze whether this effect
or the decay of photons into axions can explain the large scale anisotropies
which have been observed in the polarizations of quasars and radio galaxies. We
also comment on the possibility that the axion-photon mixing can explain the
dimming of distant supernovae.Comment: 18 pages, 1 figur
Chiral-symmetry restoration in the linear sigma model at nonzero temperature and baryon density
We study the chiral phase transition in the linear sigma model with 2 quark
flavors and colors. One-loop calculations predict a first-order phase
transition at both and . We also discuss the phase diagram
and make a comparison with a thermal parametrization of existing heavy-ion
experimental data.Comment: 12 pages, 6 ps-figures, LaTe
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