102 research outputs found

### When does the Hawking into Unruh mapping for global embeddings work?

We discuss for which smooth global embeddings of a metric into a Minkowskian
spacetime the Hawking into Unruh mapping takes place. There is a series of
examples of global embeddings into the Minkowskian spacetime (GEMS) with such
mapping for physically interesting metrics. These examples use Fronsdal-type
embeddings for which timelines are hyperbolas. In the present work we show that
for some new embeddings (non Fronsdal-type) of the Schwarzschild and
Reissner-Nordstrom metrics there is no mapping. We give also the examples of
hyperbolic and non hyperbolic type embeddings for the de Sitter metric for
which there is no mapping. For the Minkowski metric where there is no Hawking
radiation we consider a non trivial embedding with hyperbolic timelines, hence
in the ambient space the Unruh effect takes place, and it follows that there is
no mapping too. The considered examples show that the meaning of the Hawking
into Unruh mapping for global embeddings remains still insufficiently clear and
requires further investigations.Comment: LaTeX, 10 pages. This is extended version of the pape

### Gravity as a field theory in flat space-time

We propose a formulation of gravity theory in the form of a field theory in a
flat space-time with a number of dimensions greater than four. Configurations
of the field under consideration describe the splitting of this space-time into
a system of mutually noninteracting four-dimensional surfaces. Each of these
surfaces can be considered our four-dimensional space-time. If the theory
equations of motion are satisfied, then each surface satisfies the
Regge-Teitelboim equations, whose solutions, in particular, are solutions of
the Einstein equations. Matter fields then satisfy the standard equations, and
their excitations propagate only along the surfaces. The formulation of the
gravity theory under consideration could be useful in attempts to quantize it.Comment: LaTeX, 11 page

### Calculation of the Mass Spectrum of QED-2 in Light-Front Coordinates

With the aim of a further investigation of the nonperturbative Hamiltonian
approach in gauge field theories, the mass spectrum of QED-2 is calculated
numerically by using the corrected Hamiltonian that was constructed previously
for this theory on the light front. The calculations are performed for a wide
range of the ratio of the fermion mass to the fermion charge at all values of
the parameter \hat\theta related to the vacuum angle \theta. The results
obtained in this way are compared with the results of known numerical
calculations on a lattice in Lorentz coordinates. A method is proposed for
extrapolating the values obtained within the infrared-regularized theory to the
limit where the regularization is removed. The resulting spectrum agrees well
with the known results in the case of \theta=0; in the case of \theta=\pi,
there is agreement at small values of the fermion mass (below the
phase-transition point).Comment: LaTex 2.09, 20 pages, 7 figures. New improved expression for the
effective LF Hamiltonian was adde

- â€¦