590 research outputs found
A Five Dimensional Perspective on Many Particles in the Snyder basis of Double Special Relativity
After a brief summary of Double Special Relativity (DSR), we concentrate on a
five dimensional procedure, which consistently introduce coordinates and
momenta in the corresponding four-dimensional phase space, via a Hamiltonian
approach. For the one particle case, the starting point is a de Sitter momentum
space in five dimensions, with an additional constraint selected to recover the
mass shell condition in four dimensions. Different basis of DSR can be
recovered by selecting specific gauges to define the reduced four dimensional
degrees of freedom. This is shown for the Snyder basis in the one particle
case. We generalize the method to the many particles case and apply it again to
this basis. We show that the energy and momentum of the system, given by the
dynamical variables that are generators of translations in space and time and
which close the Poincar\'e algebra, are additive magnitudes. From this it
results that the rest energy (mass) of a composite object does not have an
upper limit, as opposed to a single component particle which does.Comment: 12 pages, no figures, AIP Conf. Pro
Duality for massive spin two theories in arbitrary dimensions
Using the parent Lagrangian approach we construct a dual formulation, in the
sense originally proposed by Curtright and Freund, of a massive spin two
Fierz-Pauli theory in arbitrary dimensions . This is achieved in terms of a
mixed symmetry tensor , without the need of
auxiliary fields. The relation of this method with an alternative formulation
based on a gauge symmetry principle proposed by Zinoviev is elucidated. We show
that the latter formulation in four dimensions, with a given gauge fixing
together with a definite sequence of auxiliary fields elimination via their
equations of motion, leads to the parent Lagrangian already considered by West
completed by a Fierz-Pauli mass term, which in turns yields the
Curtright-Freund action. This motivates our generalization to arbitrary
dimensions leading to the corresponding extension of the four dimensional
result. We identify the transverse true degrees of freedom of the dual theory
and verify that their number is in accordance with those of the massive
Fierz-Pauli field.Comment: 14 pages, no figures, revtex 4. Some new comments and explanations
have been added and the notation homogeneize
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Reality and causality in quantum gravity modified electrodynamics
We present a general description of the propagation properties of quantum
gravity modified electrodynamics characterized by constitutive relations up to
second order in the correction parameter. The effective description corresponds
to an electrodynamics in a dispersive and absorptive non-local medium, where
the Green functions and the refraction indices can be explicitly calculated.
The reality of the electromagnetic field together with the requirement of
causal propagation in a given referrence frame leads to restrictions in the
form of such refraction indices. In particular, absorption must be present in
all cases and, contrary to the usual assumption, it is the dominant aspect in
those effective models which exhibit linear effects in the correction parameter
not related to birefringence. In such a situation absorption is linear while
propagation is quadratical in the correction parameter.Comment: 15 pages, LaTex, minor changes to clarify some points, version
accepted for publicatio
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