224 research outputs found
Natural fermion mass hierarchy and mixings in family unification
We present an SU(9) model of family unification with three light chiral
families, and a natural hierarchy of charged fermion masses and mixings. The
existence of singlet right handed neutrions with masses about two orders of
magnitude smaller than the GUT scale, as needed to understand the light
neutrinos masses via the see-saw mechanism, is compelling in our model.Comment: 7 pages, no figur
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
Particle Physics Models, Topological Defects and Electroweak Baryogenesis
We demonstrate the viability of electroweak baryogenesis scenarios in which
the necessary departure from equilibrium is realized by the evolution of a
network of topological defects. We consider several effective models of TeV
physics, each addressing a fundamental particle physics problem, and in which
the conditions necessary for defect-mediated electroweak baryogenesis are
naturally satisfied. In each case we compare the strength of the model with
that expected from scenarios in which baryogenesis proceeds with the
propagation of critical bubbles.Comment: 12 pages, LaTeX, no figure
Models for Little Rip Dark Energy
We examine in more detail specific models which yield a little rip cosmology,
i.e., a universe in which the dark energy density increases without bound but
the universe never reaches a finite-time singularity. We derive the conditions
for the little rip in terms of the inertial force in the expanding universe and
present two representative models to illustrate in more detail the difference
between little rip models and those which are asymptotically de Sitter. We
derive conditions on the equation of state parameter of the dark energy to
distinguish between the two types of models. We show that coupling between dark
matter and dark energy with a little rip equation of state can alter the
evolution, changing the little rip into an asymptotic de Sitter expansion. We
give conditions on minimally-coupled phantom scalar field models and on
scalar-tensor models that indicate whether or not they correspond to a little
rip expansion. We show that, counterintuitively, despite local instability, a
little-rip cosmology has an infinite lifetime.Comment: LaTeX, 10 pages, no figure, version to appear in Phys.Lett
The Little Rip
We examine models in which the dark energy density increases with time (so
that the equation-of-state parameter w satisfies w < -1), but w approaches -1
asymptotically, such that there is no future singularity. We refine previous
calculations to determine the conditions necessary to produce this evolution.
Such models can display arbitrarily rapid expansion in the near future, leading
to the destruction of all bound structures (a "little rip"). We determine
observational constraints on these models and calculate the point at which the
disintegration of bound structures occurs. For the same present-day value of w,
a big rip with constant w disintegrates bound structures earlier than a little
rip.Comment: 5 pages, 1 figur
Scalar dark energy models mimicking CDM with arbitrary future evolution
Dark energy models with various scenarios of evolution are considered from
the viewpoint of the formalism for the equation of state. It is shown that
these models are compatible with current astronomical data. Some of the models
presented here evolve arbitrarily close to CDM up to the present, but
diverge in the future into a number of different possible asymptotic states,
including asymptotic de-Sitter (pseudo-rip) evolution, little rips with
disintegration of bound structures, and various forms of finite-time future
singularities. Therefore it is impossible from observational data to determine
whether the universe will end in a future singularity or not. We demonstrate
that the models under consideration are stable for a long period of time
(billions of years) before entering a Little Rip/Pseudo-Rip induced dissolution
of bound structures or before entering a soft finite-time future singularity.
Finally, the physical consequences of Little Rip, Type II, III and Big Crush
singularities are briefly compared.Comment: 15 pages, 1 figure, version to appear in Physics Letters
Blood and saliva-derived exomes from healthy Caucasian subjects do not display overt evidence of somatic mosaicism
Somatic mosaicism is a normal occurrence during development in the tissues and organs. As part of establishing a “healthy population “(HP) background or base-line, we investigated whether such mosaicism can be routinely detected in the circulating DNA secured from a rigorously designed healthy human liquid biopsy clinical trial (saliva, blood). We deployed next generation (NG) whole exome sequencing (WES) at median exome coverage rates of 97.2 % (-to-30x) and 70.0 % (-to-100x). We found that somatic mosaicism is not detectable by such standard bulk WES sequencing assays in saliva and blood DNA in 24 normal healthy Caucasians of both sexes from 18 to 60 years of age. We conclude that for circulating DNA using standard WES no novel somatic mutational variants can be detected in protein-coding regions of normal healthy subjects. This implies that the extent within normal tissues of somatic mosaicism must be at a lower level, below the detection threshold, for these circulating DNA WES read depths. © 2020 The Author(s
Of CP and other Gauge Symmetries in String Theory
We argue that \CP is a gauge symmetry in string theory. As a consequence, \CP
cannot be explicitly broken either perturbatively or non-pertubatively; there
can be no non-perturbative \CP-violating parameters. String theory is thus an
example of a theory where all angles arise due to spontaneous \CP
violation, and are in principle calculable.Comment: 8 page
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