7,790 research outputs found
Particle-dependent deformations of Lorentz symmetry
I here investigate what is arguably the most significant residual challenge
for the proposal of phenomenologically viable "DSR deformations" of
relativistic kinematics, which concerns the description of composite particles,
such as atoms. In some approaches to the formalization of possible scenarios
for DSR-deformation of Lorentz symmetry it emerges that composite particles
should have relativistic properties different from the ones of their
constituent "fundamental particles", but these previous results provided no
clue as to how the mismatch of relativistic properties could be consistently
implemented. I show that it is possible to implement a fully consistent
DSR-relativistic description of kinematics endowing different types of
particles with suitably different deformed-Lorentz-symmetry properties. I also
contemplate the possibility that some types of particles (or macroscopic
bodies) behave according to completely undeformed special relativity, which in
particular might apply to the DSR description of the macroscopic bodies that
constitute measuring devices ("observers"). The formalization is also
applicable to cases where different fundamental particles have different
relativistic properties, leading to a type of phenomenology which I illustrate
by considering possible applications to the ongoing analyses of the
"Lorentz-symmetry anomaly" that was recently tentatively reported by the OPERA
collaboration. Some of the new elements here introduced in the formulation of
relativistic kinematics appear to also provide the starting point for the
development of a correspondingly novel mathematical formulation of
spacetime-symmetry algebras.Comment: v2: added one more example of conservation law for interactions
involving particles with different relativistic propertie
Kinematical solution of the UHE-cosmic-ray puzzle without a preferred class of inertial observers
Among the possible explanations for the puzzling observations of cosmic rays
above the GZK cutoff there is growing interest in the ones that represent
kinematical solutions, based either on general formulations of particle physics
with small violations of Lorentz symmetry or on a quantum-gravity-motivated
scheme for the breakup of Lorentz symmetry. An unappealing aspect of these
cosmic-ray-puzzle solutions is that they require the existence of a preferred
class of inertial observers. Here I propose a new kinematical solution of the
cosmic-ray puzzle, which does not require the existence of a preferred class of
inertial observers. My proposal is a new example of a type of relativistic
theories, the so-called "doubly-special-relativity" theories, which have
already been studied extensively over the last two years. The core ingredient
of the proposal is a deformation of Lorentz transformations in which also the
Planck scale (in addition to the speed-of-light scale ) is described
as an invariant. Just like the introduction of the invariant requires a
deformation of the Galileian transformations into the Lorentz transformations,
the introduction of the invariant requires a deformation of the Lorentz
transformations, but there is no special class of inertial observers. The
Pierre Auger Observatory and the GLAST space telescope should play a key role
in future developments of these investigations. I also emphasize that the
doubly-special-relativity theory here proposed, besides being the first one to
provide a solution for the cosmic-ray puzzle, is also the first one in which a
natural description of macroscopic bodies is achieved, and may find
applications in the context of a recently-proposed dark-energy scenario.Comment: LaTex (revtex), 9 page
General Very Special Relativity is Finsler Geometry
We ask whether Cohen and Glashow's Very Special Relativity model for Lorentz
violation might be modified, perhaps by quantum corrections, possibly producing
a curved spacetime with a cosmological constant. We show that its symmetry
group ISIM(2) does admit a 2-parameter family of continuous deformations, but
none of these give rise to non-commutative translations analogous to those of
the de Sitter deformation of the Poincar\'e group: spacetime remains flat. Only
a 1-parameter family DISIM_b(2) of deformations of SIM(2) is physically
acceptable. Since this could arise through quantum corrections, its
implications for tests of Lorentz violations via the Cohen-Glashow proposal
should be taken into account. The Lorentz-violating point particle action
invariant under DISIM_b(2) is of Finsler type, for which the line element is
homogeneous of degree 1 in displacements, but anisotropic. We derive
DISIM_b(2)-invariant wave equations for particles of spins 0, 1/2 and 1. The
experimental bound, , raises the question ``Why is the
dimensionless constant so small in Very Special Relativity?''Comment: 4 pages, minor corrections, references adde
Is Nothing Sacred? Vacuum Energy, Supersymmetry and Lorentz Breaking from Recoiling D branes
Classical superstring vacua have zero vacuum energy and are supersymmetric
and Lorentz-invariant. We argue that all these properties may be destroyed when
quantum aspects of the interactions between particles and non-perturbative
vacuum fluctuations are considered. A toy calculation of string/D-brane
interactions using a world-sheet approach indicates that quantum recoil effects
- reflecting the gravitational back-reaction on space-time foam due to the
propagation of energetic particles - induce non-zero vacuum energy that is
linked to supersymmetry breaking and breaks Lorentz invariance. This model of
space-time foam also suggests the appearance of microscopic event horizons.Comment: 28 pages LaTeX, 5 eps figures, talk presented by DVN at 4th
International Symposium On Sources And Detection Of Dark Matter In The
Universe (DM 2000), Marina del Rey, California, 20-23 Feb 200
OPERA neutrinos and relativity
In a recent study, Cohen and Glashow argue that superluminal neutrinos of the
type recently reported by OPERA should be affected by anomalous Cherenkov-like
processes. This causes them to loose much of their energy before reaching the
OPERA detectors. Related concerns were reported also by Gonzalez-Mestres and Bi
et. al., who argued that pions cannot decay to superluminal neutrinos over part
of the energy range studied by OPERA. We observe here that these arguments are
set within a framework in which Lorentz symmetry is broken, by the presence of
a preferred frame. We further show that these anomalous processes are forbidden
if Lorentz symmetry is instead "deformed", preserving the relativity of
inertial frames. These deformations add non-linear terms to energy momentum
relations, conservation laws and Lorentz transformations in a way that is
consistent with the relativity of inertial observers.Comment: 5 pages, some citations added; in v3 a footnote added and minor
changes in the text made, the final version to appear in MPL
Deforming the Maxwell-Sim Algebra
The Maxwell alegbra is a non-central extension of the Poincar\'e algebra, in
which the momentum generators no longer commute, but satisfy
. The charges commute with the momenta,
and transform tensorially under the action of the angular momentum generators.
If one constructs an action for a massive particle, invariant under these
symmetries, one finds that it satisfies the equations of motion of a charged
particle interacting with a constant electromagnetic field via the Lorentz
force. In this paper, we explore the analogous constructions where one starts
instead with the ISim subalgebra of Poincar\'e, this being the symmetry algebra
of Very Special Relativity. It admits an analogous non-central extension, and
we find that a particle action invariant under this Maxwell-Sim algebra again
describes a particle subject to the ordinary Lorentz force. One can also deform
the ISim algebra to DISim, where is a non-trivial dimensionless
parameter. We find that the motion described by an action invariant under the
corresponding Maxwell-DISim algebra is that of a particle interacting via a
Finslerian modification of the Lorentz force.Comment: Appendix on Lifshitz and Schrodinger algebras adde
Planck-scale deformation of Lorentz symmetry as a solution to the UHECR and the TeV- paradoxes
One of the most puzzling current experimental physics paradoxes is the
arrival on Earth of Ultra High Energy Cosmic Rays with energies above the GZK
threshold. The recent observation of 20TeV photons from Mk 501 is another
somewhat similar paradox. Several models have been proposed for the UHECR
paradox. No solution has yet been proposed for the TeV- paradox.
Remarkably, the drastic assumption of a violation of ordinary Lorentz
invariance would resolve both paradoxes. We present a formalism for the
description of the type of Lorentz-invariance deformation (LID) that could be
induced by non-trivial short-distance structure of space-time, and we show that
this formalism is well suited for comparison of experimental data with LID
predictions. We use the UHECR and TeV- data, as well as bounds on
time-of-flight differences between photons of different energies, to constrain
the LID parameter space. A model with only two parameters, an energy scale and
a dimensionless parameter characterizing the functional dependence on the
energy scale, is shown to be sufficient to solve both the UHECR and the
TeV- threshold anomalies while satisfying the time-of-flight bounds.
The allowed region of the two-parameter space is relatively small, but,
remarkably, it fits perfectly the expectations of the quantum-gravity-motivated
space-time models known to support such deformations of Lorentz invariance:
integer value of the dimensionless parameter and characteristic energy scale
constrained to a narrow interval in the neighborhood of the Planck scale.Comment: LaTex (epsfig), 20 pages, 3 figure
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