2,914 research outputs found
Cyclic Cosmology from the Little Rip
We revisit a cyclic cosmology scenario proposed in 2007 to examine whether
its hypotheses can be sustained if the underlying big rip evolution, which was
assumed there, is replaced by the recently proposed little rip. We show that
the separation into causal patches at turnaround is generally valid for a
little rip, and therefore conclude that the little rip is equally as suitable a
basis for cyclicity as is the big rip.Comment: 5 pages. arXiv admin note: substantial text overlap with
arXiv:hep-th/061021
Conformality and Gauge Coupling Unification
It has been recently proposed to embed the standard model in a conformal
gauge theory to resolve the hierarchy problem, and to avoid assuming either
grand unification or low-energy supersymmetry. By model building based on
string-field duality we show how to maintain the successful prediction of an
electroweak mixing angle with in conformal gauge
theories with three chiral families.Comment: 8 pages LaTe
Pseudo-rip: Cosmological models intermediate between the cosmological constant and the little rip
If we assume that the cosmic energy density will remain constant or strictly
increase in the future, then the possible fates for the universe can be divided
into four categories based on the time asymptotics of the Hubble parameter
H(t): the cosmological constant, for which H(t) = constant, the big rip, for
which H(t) goes to infinity at finite time, the little rip, for which H(t) goes
to infinity as time goes to infinity, and the pseudo-rip, for which H(t) goes
to a constant as time goes to infinity. Here we examine the last of these
possibilities in more detail. We provide models that exemplify the pseudo-rip,
which is an intermediate case between the cosmological constant and the little
rip. Structure disintegration in the pseudo-rip depends on the model
parameters. We show that pseudo-rip models for which the density and Hubble
parameter increase monotonically can produce an inertial force which does not
increase monotonically, but instead peaks at a particular future time and then
decreases.Comment: 4 pages, 2 figures, title changed to agree with published versio
Virtual bilepton effects in polarized Moller scattering
We investigate the indirect effects of heavy vector bileptons being exchanged
in polarized Moller scattering, at the next generation of linear colliders.
Considering both longitudinal and transverse beam polarization, and accounting
for initial-state radiation, beamstrahlung and beam energy spread, we discuss
how angular distributions and asymmetries can be used to detect clear signals
of virtual bileptons, and the possibility of distinguishing theoretical models
that incorporate these exotic particles. We then estimate 95% C.L. bounds on
the mass of these vector bileptons and on their couplings to electrons.Comment: 19 pages, 10 figure
String Approach to QCD Quarks in Fundamental Representations
Straightforward use of AdS/CFT correspondence can give QCD with quarks in
adjoint representations. Using an asymmetric orbifold approach we obtain
nonsupersymmetric QCD with four quark flavors in fundamental representations of
color.Comment: 8 pages, 1 figure. Talk at Eighth Workshop on Nonperturbative Quantum
Chromodynamics, l'Institut Astrophysique de Paris, June 7-11, 200
Outcome from Spontaneous CP Violation for B Decays
In the aspon model solution of the strong problem, there is a gauged
symmetry, spontaneously broken by the same vacuum expectation value
which breaks , whose massive gauge boson provides an additional mechanism
of weak violation. We calculate the asymmetries in decays for the
aspon model and show that they are typically smaller than those predicted from
the standard model. A linear relation between the asymmetries of different
decay processes is obtained.Comment: REVTEX, 9 pages, IFP-486-UNC, NSF-PT-94-1, and UDHEP-01-9
Mersenne Primes, Polygonal Anomalies and String Theory Classification
It is pointed out that the Mersenne primes and associated
perfect numbers play a significant role in string
theory; this observation may suggest a classification of consistent string
theories.Comment: 10 pages LaTe
Search for Heavy Leptons at Hadron Colliders
Four models are considered which contain heavy leptons beyond the three
families of the standard model. Two are fourth-generation extensions of the
standard model in which the right-handed heavy leptons are either isosinglets
or in an isodoublet; the other two are motivated by the aspon model of CP
violation. In all these models, the heavy neutrino can either be heavier than,
or comparable in mass to, the charged lepton leading to the possibility that
the charged lepton is very long-lived. Production cross section and signatures
for the heavy leptons are computed for the SSC and LHC.Comment: 17 pages(8 figures are not included),TRI-PP-92-9
Production of doubly charged vector bilepton pairs at colliders
The production of pairs of doubly charged vector bileptons is studied at
future colliders. The unpolarized cross--section for the
subprocess is analytically calculated and
convoluted to predict the number of events in the complete process. The gauge or non--gauge character of the
vector bilepton is discussed. It is found that as a consequence
of its spectacular signature, as it decays dominantly into two identical
charged leptons, and also due to its charge contents, which significantly
enhance the cross--section, the detection of this class of particles with mass
in the sub--TeV region can be at the reach of these colliders. The
model--independent nature of our results is stressed.Comment: 9 pages, 7 figures, submitted to physical review
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