13 research outputs found
From New to Large Field Inflation: Comparison with WMAP3
We briefly summarize and update a class of inflationary models from the early
eighties based on a quartic (Coleman-Weinberg) potential for a gauge singlet
scalar (inflaton) field. For vacuum energy scales comparable to the grand
unification scale, the scalar spectral index n_s=0.94-0.97, in very good
agreement with the WMAP three year results. The tensor to scalar ratio r<~0.14
while alpha=dn_s/d ln k=~-10^-3. For vacuum energy scales >~10^16 GeV, the
inflationary scenario switches from `new' to `large-field' (V\propto\phi^2)
inflation. An SO(10) version naturally explains the observed baryon asymmetry
via non-thermal leptogenesis.Comment: 7 pages, 4 figures, 1 table. Based on a talk given by Q. Shafi at the
2nd International Conference on The Dark Side of the Universe (DSU 2006),
Madrid (Spain), 20-24 June 200
Smooth hybrid inflation in supergravity with a running spectral index and early star formation
It is shown that in a smooth hybrid inflation model in supergravity adiabatic
fluctuations with a running spectral index with \ns >1 on a large scale and
\ns <1 on a smaller scale can be naturally generated, as favored by the
first-year data of WMAP. It is due to the balance between the nonrenormalizable
term in the superpotential and the supergravity effect. However, since smooth
hybrid inflation does not last long enough to reproduce the central value of
observation, we invoke new inflation after the first inflation. Its initial
condition is set dynamically during smooth hybrid inflation and the spectrum of
fluctuations generated in this regime can have an appropriate shape to realize
early star formation as found by WMAP. Hence two new features of WMAP
observations are theoretically explained in a unified manner.Comment: 12 pages, 1 figure, to appear in Phys. Rev.
P-term, D-term and F-term inflation
P-term inflation is a version of hybrid inflation which naturally appears in
some brane inflation models. It was introduced in the framework of N=2
supersymmetric gauge theory where superconformal SU(2,2|2) symmetry is broken
down to N=2 supersymmetry by the vev of the auxiliary triplet field P.
Depending on the direction of this vev, one can get either D-term inflation or
F-term inflation with a particular relation between Yukawa and gauge coupling,
or a mix of these models. We show that F and D models, before coupling to
gravity is included, are related by a change of variables. Coupling of this
model to N=1 supergravity breaks this symmetry and introduces a class of P-term
models interpolating between D-term and F-term inflation. The difference
between these models is determined by the direction of the vector P, which
depends on the fluxes in the underlying D3/D7 model of brane inflation. We
discuss cosmological consequences of various versions of P-term inflation.Comment: 18 pages, a footnote is adde
Constraints from Solar and Reactor Neutrinos on Unparticle Long-Range Forces
We have investigated the impact of long-range forces induced by unparticle
operators of scalar, vector and tensor nature coupled to fermions in the
interpretation of solar neutrinos and KamLAND data. If the unparticle couplings
to the neutrinos are mildly non-universal, such long-range forces will not
factorize out in the neutrino flavour evolution. As a consequence large
deviations from the observed standard matter-induced oscillation pattern for
solar neutrinos would be generated. In this case, severe limits can be set on
the infrared fix point scale, Lambda_u, and the new physics scale, M, as a
function of the ultraviolet (d_UV) and anomalous (d) dimension of the
unparticle operator. For a scalar unparticle, for instance, assuming the
non-universality of the lepton couplings to unparticles to be of the order of a
few per mil we find that, for d_UV=3 and d=1.1, M is constrained to be M >
O(10^9) TeV (M > O(10^10) TeV) if Lambda_u= 1 TeV (10 TeV). For given values of
Lambda_u and d, the corresponding bounds on M for vector [tensor] unparticles
are approximately 100 [3/Sqrt(Lambda_u/TeV)] times those for the scalar case.
Conversely, these results can be translated into severe constraints on
universality violation of the fermion couplings to unparticle operators with
scales which can be accessible at future colliders.Comment: 13 pages, 3 figures. Minor changes due to precision in numerical
factors and correction in figure labels. References added. Conclusions remain
unchange
Black Hole Lasers Revisited
The production of Hawking radiation by a single horizon is not dependent on
the high-frequency dispersion relation of the radiated field. When there are
two horizons, however, Corley and Jacobson have shown that superluminal
dispersion leads to an amplification of the particle production in the case of
bosons. The analytic theory of this "black hole laser" process is quite
complicated, so we provide some numerical results in the hope of aiding
understanding of this interesting phenomenon. Specifically, we consider sonic
horizons in a moving fluid. The theory of elementary excitations in a
Bose-Einstein condensate provides an example of "superluminal" (Bogoliubov)
dispersion, so we add Bogoliubov dispersion to Unruh's equation for sound in
the fluid. A white-hole/black-hole horizon pair will then display black hole
lasing. Numerical analysis of the evolution of a wave packet gives a clear
picture of the amplification process. By utilizing the similarity of a
radiating horizon to a parametric amplifier in quantum optics we also analyze
the black hole laser as a quantum-optical network.Comment: 16 page