3 research outputs found
Classical paradoxes of locality and their possible quantum resolutions in deformed special relativity
In deformed or doubly special relativity (DSR) the action of the lorentz
group on momentum eigenstates is deformed to preserve a maximal momenta or
minimal length, supposed equal to the Planck length. The classical and quantum
dynamics of a particle propagating in kappa-Minkowski spacetime is discussed in
order to examine an apparent paradox of locality which arises in the classical
dynamics. This is due to the fact that the Lorentz transformations of spacetime
positions of particles depend on their energies, so whether or not a local
event, defined by the coincidence of two or more particles, takes place appears
to depend on the frame of reference of the observer. Here it is proposed that
the paradox arises only in the classical picture, and may be resolved when the
quantum dynamics is taken into account. If so, the apparent paradoxes arise
because it is inconsistent to study physics in which Planck's constant is zero
but the Planck length is non-vanishing. This may be relevant for phenomenology
such as observations by FERMI, because at leading order there is both a direct
and a stochastic dependence of arrival time on energy, due to an additional
spreading of wavepackets.Comment: LaTeX, 28 pages, no figures, substantially revise
Cosmological tachyon from cubic string field theory
The classical dynamics of the tachyon scalar field of cubic string field
theory is considered on a cosmological background. Starting from a nonlocal
action with arbitrary tachyon potential, which encodes the bosonic and several
supersymmetric cases, we study the equations of motion in the Hamilton-Jacobi
formalism and with a generalized Friedmann equation, appliable in braneworld or
modified gravity models. The cases of cubic (bosonic) and quartic
(supersymmetric) tachyon potential in general relativity are automatically
included. We comment the validity of the slow-roll approximation, the stability
of the cosmological perturbations, and the relation between this tachyon and
the Dirac-Born-Infeld one.Comment: 20 pages JHEP style, 1 figure; v4: misprints corrected, matches the
published versio