3,162 research outputs found
Static plane symmetric relativistic fluids and empty repelling singular boundaries
We present a detailed analysis of the general exact solution of Einstein's
equation corresponding to a static and plane symmetric distribution of matter
with density proportional to pressure. We study the geodesics in it and we show
that this simple spacetime exhibits very curious properties. In particular, it
has a free of matter repelling singular boundary and all geodesics bounce off
it.Comment: 9 pages, 1 figure, accepted for publication in Classical and Quantum
Gravit
An alternative well-posedness property and static spacetimes with naked singularities
In the first part of this paper, we show that the Cauchy problem for wave
propagation in some static spacetimes presenting a singular time-like boundary
is well posed, if we only demand the waves to have finite energy, although no
boundary condition is required. This feature does not come from essential
self-adjointness, which is false in these cases, but from a different
phenomenon that we call the alternative well-posedness property, whose origin
is due to the degeneracy of the metric components near the boundary.
Beyond these examples, in the second part, we characterize the type of
degeneracy which leads to this phenomenon.Comment: 34 pages, 3 figures. Accepted for publication in Class. Quantum Gra
On gauge invariant regularization of fermion currents
We compare Schwinger and complex powers methods to construct regularized
fermion currents. We show that although both of them are gauge invariant they
not always yield the same result.Comment: 10 pages, 1 figur
Duality and bosonization in Schwinger-Keldysh formulation
We present a path-integral bosonization approach for systems out of
equilibrium based on a duality transformation of the original Dirac fermion
theory combined with the Schwinger-Keldysh time closed contour technique, to
handle the non-equilibrium situation. The duality approach to bosonization that
we present is valid for space-time dimensions leading for to
exact results. In this last case we present the bosonization rules for fermion
currents, calculate current-current correlation functions and establish the
connection between the fermionic and bosonic distribution functions in a
generic, nonequilibrium situation.Comment: 16 pages, 1 figur
The electromagnetic energy-momentum tensor
We clarify the relation between canonical and metric energy-momentum tensors.
In particular, we show that a natural definition arises from Noether's Theorem
which directly leads to a symmetric and gauge invariant tensor for
electromagnetic field theories on an arbitrary space-time of any dimension
Exotic galilean symmetry and the Hall effect
The ``Laughlin'' picture of the Fractional Quantum Hall effect can be derived
using the ``exotic'' model based on the two-fold centrally-extended planar
Galilei group. When coupled to a planar magnetic field of critical strength
determined by the extension parameters, the system becomes singular, and
``Faddeev-Jackiw'' reduction yields the ``Chern-Simons'' mechanics of Dunne,
Jackiw, and Trugenberger. The reduced system moves according to the Hall law.Comment: Talk given by P. A. Horvathy at the Joint APCTP- Nankai Symposium.
Tianjin (China), Oct.2001. To appear in the Proceedings, to be published by
Int. Journ. Mod. Phys. B. 7 pages, LaTex, IJMPB format. no figure
Dirac Operator on a disk with global boundary conditions
We compute the functional determinant for a Dirac operator in the presence of
an Abelian gauge field on a bidimensional disk, under global boundary
conditions of the type introduced by Atiyah-Patodi-Singer. We also discuss the
connection between our result and the index theorem.Comment: RevTeX, 11 pages. References adde
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