11 research outputs found
A new spin-2 self-dual model in
There are three self-dual models of massive particles of helicity +2 (or -2)
in . Each model is of first, second, and third-order in derivatives.
Here we derive a new self-dual model of fourth-order, \cL {SD}^{(4)}, which
follows from the third-order model (linearized topologically massive gravity)
via Noether embedment of the linearized Weyl symmetry. In fact, each self-dual
model can be obtained from the previous one \cL {SD}^{(i)} \to \cL
{SD}^{(i+1)}, i=1,2,3 by the Noether embedment of an appropriate gauge
symmetry, culminating in \cL {SD}^{(4)}. The new model may be identified with
the linearized version of \cL {HDTMG} = \epsilon^{\mu\nu\rho}
\Gamma_{\mu\gamma}^\epsilon (\p_\nu\Gamma_{\epsilon\rho}^\gamma +
(2/3)\Gamma_{\nu\delta}^\gamma \Gamma_{\rho\epsilon}^\delta) /8 m +
\sqrt{-g}(R_{\mu\nu} R^{\nu\mu} - 3 R^2/8) /2 m^2 . We also construct a master
action relating the third-order self-dual model to \cL {SD}^{(4)} by means of
a mixing term with no particle content which assures spectrum equivalence of
\cL {SD}^{(4)} to other lower-order self-dual models despite its pure higher
derivative nature and the absence of the Einstein-Hilbert action. The relevant
degrees of freedom of \cL {SD}^{(4)} are encoded in a rank-two tensor which
is symmetric, traceless and transverse due to trivial (non-dynamic) identities,
contrary to other spin-2 self-dual models. We also show that the Noether
embedment of the Fierz-Pauli theory leads to the new massive gravity of
Bergshoeff, Hohm and Townsend.Comment: 14 pages, no figures, typos fixed, reference (19) modifie
On the influence of a Coulomb-like potential induced by the Lorentz symmetry breaking effects on the Harmonic Oscillator
In this work, we obtain bound states for a nonrelativistic spin-half neutral
particle under the influence of a Coulomb-like potential induced by the Lorentz
symmetry breaking effects. We present a new possible scenario of studying the
Lorentz symmetry breaking effects on a nonrelativistic quantum system defined
by a fixed space-like vector field parallel to the radial direction interacting
with a uniform magnetic field along the z-axis. Furthermore, we also discuss
the influence of a Coulomb-like potential induced by Lorentz symmetry violation
effects on the two-dimensional harmonic oscillator.Comment: 14 pages, no figure, this work has been accepted for publication in
The European Physical Journal Plu
Consistency analysis of a nonbirefringent Lorentz-violating planar model
In this work analyze the physical consistency of a nonbirefringent
Lorentz-violating planar model via the analysis of the pole structure of its
Feynman propagators. The nonbirefringent planar model, obtained from the
dimensional reduction of the CPT-even gauge sector of the standard model
extension, is composed of a gauge and a scalar fields, being affected by
Lorentz-violating (LIV) coefficients encoded in the symmetric tensor
. The propagator of the gauge field is explicitly evaluated
and expressed in terms of linear independent symmetric tensors, presenting only
one physical mode. The same holds for the scalar propagator. A consistency
analysis is performed based on the poles of the propagators. The isotropic
parity-even sector is stable, causal and unitary mode for .
On the other hand, the anisotropic sector is stable and unitary but in general
noncausal. Finally, it is shown that this planar model interacting with a
Higgs field supports compactlike vortex configurations.Comment: 11 pages, revtex style, final revised versio
Stationary solutions for the parity-even sector of the CPT-even and Lorentz-covariance-violating term of the standard model extension
In this work, we focus on some properties of the parity-even sector of the
CPT-even electrodynamics of the standard model extension. We analyze how the
six non-birefringent terms belonging to this sector modify the static and
stationary classical solutions of the usual Maxwell theory. We observe that the
parity-even terms do not couple the electric and magnetic sectors (at least in
the stationary regime). The Green's method is used to obtain solutions for the
field strengths E and B at first order in the Lorentz- covariance-violating
parameters. Explicit solutions are attained for point-like and spatially
extended sources, for which a dipolar expansion is achieved. Finally, it is
presented an Earth-based experiment that can lead (in principle) to an upper
bound on the anisotropic coefficients as stringent as
Comment: 8 pages, revtex style, revised published version, to appear in EPJC
(2009
Naturalness and theoretical constraints on the Higgs boson mass
Arbitrary regularization dependent parameters in Quantum Field Theory are
usually fixed on symmetry or phenomenology grounds. We verify that the
quadratically divergent behavior responsible for the lack of naturalness in the
Standard Model (SM) is intrinsically arbitrary and regularization dependent.
While quadratic divergences are welcome for instance in effective models of low
energy QCD, they pose a problem in the SM treated as an effective theory in the
Higgs sector. Being the very existence of quadratic divergences a matter of
debate, a plausible scenario is to search for a symmetry requirement that could
fix the arbitrary coefficient of the leading quadratic behavior to the Higgs
boson mass to zero. We show that this is possible employing consistency of
scale symmetry breaking by quantum corrections. Besides eliminating a
fine-tuning problem and restoring validity of perturbation theory, this
requirement allows to construct bounds for the Higgs boson mass in terms of
(where is the renormalized Higgs mass and
is the 1-loop Higgs mass correction). Whereas
(perturbative regime) in this scenario allows the Higgs boson mass around the
current accepted value, the inclusion of the quadratic divergence demands
arbitrarily large to reach that experimental value.Comment: 6 pages, 4 figure