1,870 research outputs found
A "nu" look at gravitational waves: The black hole birth rate from neutrinos combined with the merger rate from LIGO
We make projections for measuring the black hole birth rate from the diffuse
supernova neutrino background (DSNB) by future neutrino experiments, and
constrain the black hole merger fraction , when combined with
information on the black hole merger rate from gravitational wave experiments
such as LIGO. The DSNB originates from neutrinos emitted by all the supernovae
in the Universe, and is expected to be made up of two components: neutrinos
from neutron-star-forming supernovae, and a sub-dominant component at higher
energies from black-hole-forming "unnovae". We perform a Markov Chain Monte
Carlo analysis of simulated data of the DSNB in an experiment similar to
Hyper-Kamiokande, focusing on this second component. Since all knowledge of the
neutrino emission from unnovae comes from simulations of collapsing stars, we
choose two sets of priors: one where the unnovae are well-understood and one
where their neutrino emission is poorly known. By combining the black hole
birth rate from the DSNB with projected measurements of the black hole merger
rate from LIGO, we show that the fraction of black holes which lead to binary
mergers observed today could be constrained to be within the range
at confidence,
after ten years of running an experiment like Hyper-Kamiokande.Comment: 19 pages, 6 figures. v3: Matches version accepted to JCA
Radion Assisted Gauge Inflation
We propose an extension to the recently proposed extranatural or gauge
inflation scenario in which the radius modulus field around which the Wilson
loop is wrapped assists inflation as it shrinks. We discuss how this might lead
to more generic initial conditions for inflation.Comment: 10 pages, 2 figure
Temporal variation of coupling constants and nucleosynthesis
We investigate the triple-alpha process and the Oklo phenomenon to obtain
constraints on possible cosmological time variations of fundamental constants.
Specifically we study cosmological temporal constraints for the fine structure
constant and nucleon and meson masses.Comment: 4 pages. Proceedings of the Nuclear Physics in Astrophysics
Conference, Debrecen, Hungary, September 30 - October 3, 2002. To be
published in Nuc. Phys.
Geometrical CP violation in multi-Higgs models
We introduce several methods to obtain calculable phases with geometrical
values that are independent of arbitrary parameters in the scalar potential.
These phases depend on the number of scalars and on the order of the discrete
non-Abelian group considered. Using these methods we present new geometrical CP
violation candidates with vacuum expectation values that must violate CP (the
transformation that would make them CP conserving is not a symmetry of the
potential). We also extend to non-renormalisable potentials the proof that more
than two scalars are needed to obtain these geometrical CP violation
candidates.Comment: 8 pages, 2 figures. v2: table added, accepted by JHE
Euclidean three-point function in loop and perturbative gravity
We compute the leading order of the three-point function in loop quantum
gravity, using the vertex expansion of the Euclidean version of the new spin
foam dynamics, in the region of gamma<1. We find results consistent with Regge
calculus in the limit gamma->0 and j->infinity. We also compute the tree-level
three-point function of perturbative quantum general relativity in position
space, and discuss the possibility of directly comparing the two results.Comment: 16 page
Comments on the kinematical structure of loop quantum cosmology
We comment on the presence of spurious observables and on a subtle violation
of irreducibility in loop quantum cosmology.Comment: 7 page
Minimal Family Unification
Absract It is proposed that there exist, within a new , a gauged
discrete group (the order 12 double dihedral group) acting as a family
symmetry. This nonabelian finite group can explain hierarchical features of
families, using an assignment for quarks and leptons dictated by the
requirements of anomaly cancellation and of no additional quarks.Comment: 10 pages, IFP-701-UNC;VAND-TH-94-
Standard Cosmological Evolution in a Wide Range of f(R) Models
Using techniques from singular perturbation theory, we explicitly calculate
the cosmological evolution in a class of modified gravity models. By
considering the (m)CDTT model, which aims to explain the current acceleration
of the universe with a modification of gravity, we show that Einstein evolution
can be recovered for most of cosmic history in at least one f(R) model. We show
that a standard epoch of matter domination can be obtained in the mCDTT model,
providing a sufficiently long epoch to satisfy observations. We note that the
additional inverse term will not significantly alter standard evolution until
today and that the solution lies well within present constraints from Big Bang
Nucleosynthesis. For the CDTT model, we analyse the ``recent radiation epoch''
behaviour (a \propto t^{1/2}) found by previous authors. We finally generalise
our findings to the class of inverse power-law models. Even in this class of
models, we expect a standard cosmological evolution, with a sufficient matter
domination era, although the sign of the additional term is crucial.Comment: 15 pages, 6 figures (1 new figure), new version considers both CDTT
and mCDTT models. References added. Accepted by Phys Rev
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