25 research outputs found
Cosmology with non-minimal scalar field: graceful entrance into inflation
We propose a scenario of the beginning of inflation in which the non-vacuum
value of the scalar field that drives inflation develops dynamically due to the
non-minimal coupling to gravity. In this scenario, inflation emerges as an
intermediate stage of the evolution of the Universe, well after the Planck
epoch, from a fairly general initial state.Comment: LaTeX, uses axodraw style, 7 pages, 1 ps-figur
Neutrino masses from nonstandard supersymmetry breaking terms
Naturally small Majorana neutrino masses arise from nonstandard supersymmetry
breaking terms. This mechanism works in the minimal supersymmetric framework
and does not require extra particles or new mass scales. It could also be
responsible for proton decay even in the absence of Grand Unification.Comment: 7 pages, 3 eps figures; important note on baryon number violation
added; small editorial changes mad
Zeros of tree amplitudes at rest and symmetries of mechanical systems
We consider the tree amplitudes of production of scalar particles by
particles of another kind, where both initial and final particles are at
rest and on mass shell, in a model of two scalar fields with symmetric
interaction and unequal masses. We find that these amplitudes are zero except
for the lowest possible and , and that the cancellation of the
corresponding Feynman graphs occurs due to a special symmetry of the classical
mechanical counterpart of this theory. This feature is rather general and is
inherent in various other scalar field theories.Comment: 11 pages Preprint INR-830/93, August 199
Three generations on a local vortex in extra dimensions
We develop an approach to the origin of three generations of the Standard
Model fermions from one generation in a higher-dimensional theory, where
four-dimensional fermions appear as zero modes trapped in the core of a
topological defect, and the hierarchy of masses and mixings is produced by wave
function overlaps in extra dimensions. We present a model with unbroken U(1)
symmetry where three zero modes appear on an Abrikosov-Nielsen-Olesen vortex
due to nontrivial scalar--fermion interactions.Comment: 8 pages, no figure
On the nullification of threshold amplitudes
The nullification of threshold amplitudes is considered within the
conventional framework of quantum field theory. The relevant Ward identities
for the reduced theory are derived both on path-integral and diagrammatic
levels. They are then used to prove the vanishing of tree-graph threshold
amplitudes.Comment: 16 page
Non-renormalization of induced charges and constraints on strongly coupled theories
It is shown that global fermionic charges induced in vacuum by slowly
varying, topologically non-trivial background scalar fields are not
renormalized provided that expansion in momenta of background fields is valid.
This suggests that strongly coupled theories obey induced charge matching
conditions which are analogous, but generally not equivalent, to 't Hooft
anomaly matching conditions. We give a few examples of induced charge matching.
In particular, the corresponding constraints in softly broken supersymmetric
QCD suggest non-trivial low energy mass pattern, in full accord with the
results of direct analyses.Comment: 19 pages, LaTeX, two PS figures; Submitted to special issue of Phys.
Reports dedicated to 70th birthday of L.B.Oku
Flowing to four dimensions
We analyze the properties of a model with four-dimensional brane-localized
Higgs type potential of a six dimensional scalar field satisfying the Dirichlet
boundary condition on the boundary of a transverse two-dimensional compact
space. The regularization of the localized couplings generates classical
renormalization group running. A tachyonic mass parameter grows in the
infrared, in analogy with the QCD gauge coupling in four dimensions. We find a
phase transition at a critical value of the bare mass parameter such that the
running mass parameter becomes large in the infrared precisely at the
compactification scale. Below the critical coupling, the theory is in symmetric
phase, whereas above it spontaneous symmetry breaking occurs. Close to the
phase transition point there is a very light mode in the spectrum. The massive
Kaluza-Klein spectrum at the critical coupling becomes independent of the UV
cutoff.Comment: 22 pages, LaTe
A Lorentz Invariance Violating Cosmology on the DGP Brane
We study cosmological implications of a Lorentz invariance violating
DGP-inspired braneworld scenario. A minimally coupled scalar field and a
single, fixed-norm, Lorentz-violating timelike vector field within an
interactive picture provide a wide parameter space which accounts for late-time
acceleration and transition to phantom phase of the scalar field.Comment: 23 pages, 8 figures, accepted for publication in JCA
Tree amplitudes at multiparticle threshold in a model with softly broken symmetry
Tree amplitudes of the production of two kinds of scalar particles at
threshold from one virtual particle are calculated in a model of two scalar
fields with symmetric quartic interaction and unequal masses. These
amplitudes exhibit interesting factorial and exponential behaviour at large
multiplicities. As a by-product we observe that the kinematically allowed decay
of one real particle into real particles of another kind, all at rest, has
zero tree amplitude in this model for .Comment: 17 pages. Preprint INR-823/9
QED from six-dimensional vortex and gauge anomalies
Starting from an anomaly-free Abelian Higgs model coupled to gravity in a
6-dimensional space-time we construct an effective four-dimensional theory of
charged fermions interacting with U(1) Abelian gauge field and gravity, both
localised near the core of a Nielsen-Olesen vortex configuration. We show that
an anomaly free theory in 6-dimensions can give rise to an anomalous theory in
D=4, which suggests a possibility of consistent regularisation of abelian
anomalous chiral gauge theories in four dimensions. We also show that the
spectrum of charged bulk fermions has a mass gap.Comment: Latex, 19 page