2,198 research outputs found
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
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
Entropy of Contracting Universe in Cyclic Cosmology
Following up a recent proposal \cite{BF} for a cyclic model based on phantom
dark energy, we examine the content of the contracting universe (cu) and its
entropy . We find that beyond dark energy the universe contains on
average zero or at most a single photon which if present immediately after
turnaround has infinitesimally energy which subsequently blue shifts to produce
pairs. These statements are independent of the equation of state
of dark energy provided . Thus and
if observations confirm the entropy problem is solved. We discuss
the absence of a theoretical lower bound on , then
describe an anthropic fine tuning argument that renders unlikely extremely
small . The present bound already implies a time
until turnaround of Gy.Comment: 5 pages late
Cyclic Universe and Infinite Past
We address two questions about the past for infinitely cyclic cosmology. The
first is whether it can contain an infinite length null geodesic into the past
in view of the Borde-Guth-Vilenkin (BGV) "no-go" theorem, The second is
whether, given that a small fraction of spawned universes fail to cycle, there
is an adequate probability for a successful universe after an infinite time. We
give positive answers to both questions then show that in infinite cyclicity
the total number of universes has been infinite for an arbitrarily long time.Comment: 7 pages. Clarification in discussion of infinite pas
Flavor Symmetry for Quarks and Leptons
Present data on neutrino masses and mixing favor the highly symmetric
tribimaximal neutrino mixing matrix which suggests an underlying flavor
symmetry. A systematic study of non-abelian finite groups of order
reveals that tribimaximal mixing can be derived not only from the well known
tetrahedral flavor symmetry , but also by using the binary
tetrahedral symmetry which does not contain the
tetrahedral group as a subgroup. has the further advantage that it can
also neatly accommodate the quark masses including a heavy top quark.Comment: 12 pages latex. More typos correcte
Quark mass hierarchy in 3-3-1 models
We study the mass spectrum of the quark sector in an special type I-like
model with gauge symmetry . By
considering couplings with scalar triplets at large () and small
() scales, we obtain specific zero-texture mass matrices for the
quarks which predict three massless quarks () and three massive quarks
() at the electroweak scale ( GeV). Taking into account mixing
couplings with three heavy quarks at large scales predicted by the model, the
three massless quarks obtain masses at small order that depends on the inverse
of the large scale. Thus, masses of the form
and can be obtained naturally from the gauge structure of
the model
Constraints on Deflation from the Equation of State of Dark Energy
In cyclic cosmology based on phantom dark energy the requirement that our
universe satisfy a CBE-condition ({\it Comes Back Empty}) imposes a lower bound
on the number of causal patches which separate just prior to
turnaround. This bound depends on the dark energy equation of state with . More accurate measurement of will
constrain . The critical density in the model has a lower
bound or
when the smallest bound state has size m, or m,
respectively.Comment: 23 pages, 3 figures, typos fixe
The Cabibbo Angle in a Supersymmetric D14 Model
We construct a supersymmetric model with the flavor symmetry D14 in which the
CKM matrix element |V_{ud}| can take the value |V_{ud}| =cos (pi/14) = 0.97493
implying that the Cabibbo angle theta_C is sin (theta_C) = |V_{us}| = sin
(pi/14) = 0.2225. These values are very close to those observed in experiments.
The value of |V_{ud}| (theta_C) is based on the fact that different Z2
subgroups of D14 are conserved in the up and down quark sector. In order to
achieve this, D14 is accompanied by a Z3 symmetry. The spontaneous breaking of
D14 is induced by flavons, which are scalar gauge singlets. The quark mass
hierarchy is partly due to the flavor group D14 and partly due to a
Froggatt-Nielsen symmetry U(1)_{FN} under which only the right-handed quarks
transform. The model is completely natural in the sense that the hierarchies
among the quark masses and mixing angles are generated with the help of
symmetries. The issue of the vacuum alignment of the flavons is solved up to a
small number of degeneracies, leaving four different possible values for
|V_{ud}|. Out of these, only one of them leads to a phenomenological viable
model. A study of the Z2 subgroup breaking terms shows that the results
achieved in the symmetry limit are only slightly perturbed. At the same time
they allow |V_{ud}| (theta_C) to be well inside the small experimental error
bars.Comment: 1+24 page
Primordial Black Holes, Hawking Radiation and the Early Universe
The 511 keV gamma emission from the galactic core may originate from a high
concentration () of primordial black holes (PBHs) in the core
each of whose Hawking radiation includes positrons per second.
The PBHs we consider are taken as near the lightest with longevity greater than
the age of the universe (mass kg; Schwarzschild radius
fm). These PBHs contribute only a small fraction of cold dark matter,
. This speculative hypothesis, if confirmed implies
the simultaneous discovery of Hawking radiation and an early universe phase
transition.Comment: 4 Page
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