279 research outputs found
A 3-3-1 model with low scale seesaw mechanisms
We construct a viable 3-3-1 model with two scalar triplets,
extended fermion and scalar spectrum, based on the family symmetry
and other auxiliary cyclic symmetries, whose spontaneous breaking yields the
observed pattern of SM fermion mass spectrum and fermionic mixing parameters.
In our model the SM quarks lighter than the top quark, get their masses from a
low scale Universal seesaw mechanism, the SM charged lepton masses are produced
by a Froggatt-Nielsen mechanism and the small light active neutrino masses are
generated from an inverse seesaw mechanism. The model is consistent with the
low energy SM fermion flavor data and successfully accommodates the current
Higgs diphoton decay rate and predicts charged lepton flavor violating decays
within the reach of the forthcoming experiments.Comment: 24 pages, 4 figures. Published versio
Gauge fixing in higher derivative field theories
Higher Derivative (HD) Field Theories can be transformed into second order
equivalent theories with a direct particle interpretation. In a simple model
involving abelian gauge symmetries we examine the fate of the possible gauge
fixings throughout this process. This example is a useful test bed for HD
theories of gravity and provides a nice intuitive interpretation of the "third
ghost" occurring there and in HD gauge theories when a HD gauge fixing is
adopted.Comment: 16 pages, Latex,( Preprint imaff 93/10
Inner products of resonance solutions in 1-D quantum barriers
The properties of a prescription for the inner products of the resonance
(Gamow states), scattering (Dirac kets), and bound states for 1-dimensional
quantum barriers are worked out. The divergent asypmtotic behaviour of the
Gamow states is regularized using a Gaussian convergence factor first
introduced by Zel'dovich. With this prescription, most of these states (with
discrete complex energies) are found to be orthogonal to each other, to the
bound states, and to the Dirac kets, except when they are neighbors, in which
case the inner product is divergent. Therefore, as it happens for the continuum
scattering states, the norm of the resonant ones remains non-calculable. Thus,
they exhibit properties half way between the (continuum real) Dirac-delta
orthogonality and the (discrete real) Kronecker-delta orthogonality of the
bound states.Comment: 13 pages, 2 figure
Gauge Fixing in Higher Derivative Gravity
Linearized four-derivative gravity with a general gauge fixing term is
considered. By a Legendre transform and a suitable diagonalization procedure it
is cast into a second-order equivalent form where the nature of the physical
degrees of freedom, the gauge ghosts, the Weyl ghosts, and the intriguing
"third ghosts", characteristic to higher-derivative theories, is made explicit.
The symmetries of the theory and the structure of the compensating
Faddeev-Popov ghost sector exhibit non-trivial peculiarities.Comment: 21 pages, LaTe
Dynamical variables in Gauge-Translational Gravity
Assuming that the natural gauge group of gravity is given by the group of
isometries of a given space, for a maximally symmetric space we derive a model
in which gravity is essentially a gauge theory of translations. Starting from
first principles we verify that a nonlinear realization of the symmetry
provides the general structure of this gauge theory, leading to a simple choice
of dynamical variables of the gravity field corresponding, at first order, to a
diagonal matrix, whereas the non-diagonal elements contribute only to higher
orders.Comment: 15 page
Nonlinear gauge realization of spacetime symmetries including translations
We present a general scheme for the nonlinear gauge realizations of space-time groups on coset spaces of the groups considered. In order to show the relevance of the method for the rigorous treatment of the translations in gravitational gauge theories, we apply it in particular to the affine group. This is an illustration of the family of spacetime symmetries having the form of a semidirect product H ⊗ T, where H is the stability subgroup and T are the translations. The translational component of the connection behaves like a true tensor under H when coset realizations are involved. c Plenum Publishing CorporationPeer Reviewe
Exact Renormalization Group and Running Newtonian Coupling in Higher Derivative Gravity
We discuss exact renormalization group (RG) in -gravity using effective
average action formalism. The truncated evolution equation for such a theory on
De Sitter background leads to the system of nonperturbative RG equations for
cosmological and gravitational coupling constants. Approximate solution of
these RG equations shows the appearence of antiscreening and screening
behaviour of Newtonian coupling what depends on higher derivative coupling
constants.Comment: Latex file, 9 page
Non-Linear Affine Embedding of the Dirac Field from the Multiplicity-Free SL(4,R) Unirreps
The correspondence between the linear multiplicity-free unirreps of SL(4, R)
studied by Ne'eman and {\~{S}}ija{\~{c}}ki and the non-linear realizations of
the affine group is worked out. The results obtained clarify the inclusion of
spinorial fields in a non-linear affine gauge theory of gravitation.Comment: 13 pages, plain TeX, macros include
Weak Lensing, Shear and the Cosmic Virial Theorem in a Model with a Scale-Dependent Gravitational Coupling
It is argued that, in models where the gravitational coupling is
scale-dependent, predictions concerning weak gravitational lensing and shear
are essentially similar to the ones derived from General Relativity. This is
consistent with recent negative results of observations of the MS1224, CL2218
and A1689 systems aimimg to infer from those methods the presence of dark
matter. It is shown, however, that the situation is quite different when an
analysis based on the Cosmic Virial Theorem is concerned.Comment: Footnote and references added. Version to in Gen. Relativity and
Gravitation Vol. 29 (1997
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