45 research outputs found
A Supersymmetric Model for Dark Matter and Baryogenesis Motivated by the Recent CDMS Result
We discuss a supersymmetric model for cogenesis of dark and baryonic matter
where the dark matter (DM) has mass in the 8-10 GeV range as indicated by
several direct detection searches including most recently the CDMS experiment
with the desired cross section. The DM candidate is a real scalar filed. Two
key distinguishing features of the model are the following: (i) in contrast
with the conventional WIMP dark matter scenarios where thermal freeze-out is
responsible for the observed relic density, our model uses non-thermal
production of dark matter after reheating of the universe caused by moduli
decay at temperatures below the QCD phase transition, a feature which
alleviates the relic over-abundance problem caused by small annihilation cross
section of light DM particles; (ii) baryogenesis occurs also at similar low
temperatures from the decay of TeV scale mediator particles arising from moduli
decay. A possible test of this model is the existence of colored particles with
TeV masses accessible at the LHC.Comment: 5 pages, 1 figur
Criticality and oscillatory behavior in non-Markovian Contact Process
A Non-Markovian generalization of one-dimensional Contact Process (CP) is
being introduced in which every particle has an age and will be annihilated at
its maximum age . There is an absorbing state phase transition which is
controlled by this parameter. The model can demonstrate oscillatory behavior in
its approach to the stationary state. These oscillations are also present in
the mean-field approximation which is a first-order differential equation with
time-delay. Studying dynamical critical exponents suggests that the model
belongs to the DP universlity class.Comment: 4 pages, 5 figures, to be published in Phys. Rev.
Schizophrenic Neutrinos and -less Double Beta Decay
We point out a novel possibility for neutrinos where all neutrino flavors can
be part Dirac and part Majorana. Our primary motivation for this model comes
from an attempt to use supersymmetric see-saw models to tie inflation, baryon
asymmetry of the Universe and dark matter to the neutrino sector. The idea
however could stand on its own, with or without supersymmetry. We present a
realization of this possibility within an family symmetry for neutrino
masses, where we obtain tri-bi-maximal mixing for neutrinos to the leading
order. The model predicts that for the case of inverted hierarchy, the lower
limit on the neutrino mass measured in neutrinoless double beta decay
experiments is about a factor of two larger than the usual case.Comment: 6 pages, 1 figure. Extended discussion on the pseudo-Dirac mass
splitting due to loop correction
Identifying the curvaton within MSSM
We consider inflaton couplings to MSSM flat directions and the thermalization
of the inflaton decay products, taking into account gauge symmetry breaking due
to flat direction condensates. We then search for a suitable curvaton candidate
among the flat directions, requiring an early thermally induced start for the
flat direction oscillations to facilitate the necessary curvaton energy density
dominance. We demonstrate that the supersymmetry breaking -term is crucial
for achieving a successful curvaton scenario. Among the many possible
candidates, we identify the flat direction as a viable MSSM
curvaton.Comment: 9 pages. Discussion on the evaporation of condensate added, final
version published in JCA
Cosmological bounds on large extra dimensions from non-thermal production of Kaluza-Klein modes
The existing cosmological constraints on theories with large extra dimensions
rely on the thermal production of the Kaluza-Klein modes of gravitons and
radions in the early Universe. Successful inflation and reheating, as well as
baryogenesis, typically requires the existence of a TeV-scale field in the
bulk, most notably the inflaton. The non-thermal production of KK modes with
masses of order 100 GeV accompanying the inflaton decay sets the lower bounds
on the fundamental scale M_*. For a 1 TeV inflaton, the late decay of these
modes distort the successful predictions of Big Bang Nucleosynthesis unless
M_*> 35, 13, 7, 5 and 3 TeV for 2, 3, 4, 5 and 6 extra dimensions,
respectively. This improves the existing bounds from cosmology on M_* for 4, 5
and 6 extra dimensions. Even more stringent bounds are derived for a heavier
inflaton.Comment: 17 pages, latex, 4 figure
A-term inflation and the smallness of the neutrino masses
The smallness of the neutrino masses may be related to inflation. The minimal
supersymmetric Standard Model (MSSM) with small Dirac neutrino masses already
has all the necessary ingredients for a successful inflation. In this model the
inflaton is a gauge-invariant combination of the right-handed sneutrino, the
slepton, and the Higgs field, which generate a flat direction suitable for
inflation if the Yukawa coupling is small enough. In a class of models, the
observed microwave background anisotropy and the tilted power spectrum are
related to the neutrino masses.Comment: 13 pages, 1 figure, uses JHEP3.cls, minor modifications, final
version accepted for publication in JCA
Supersymmetric Thermalization and Quasi-Thermal Universe: Consequences for Gravitinos and Leptogenesis
Motivated by our earlier paper \cite{am}, we discuss how the infamous
gravitino problem has a natural built in solution within supersymmetry.
Supersymmetry allows a large number of flat directions made up of {\it gauge
invariant} combinations of squarks and sleptons. Out of many at least {\it one}
generically obtains a large vacuum expectation value during inflation. Gauge
bosons and Gauginos then obtain large masses by virtue of the Higgs mechanism.
This makes the rate of thermalization after the end of inflation very small and
as a result the Universe enters a {\it quasi-thermal phase} after the inflaton
has completely decayed. A full thermal equilibrium is generically established
much later on when the flat direction expectation value has substantially
decareased. This results in low reheat temperatures, i.e., , which are compatible with the stringent bounds arising from the
big bang nucleosynthesis. There are two very important implications: the
production of gravitinos and generation of a baryonic asymmetry via
leptogenesis during the quasi-thermal phase. In both the cases the abundances
depend not only on an effective temperature of the quasi-thermal phase (which
could be higher, i.e., ), but also on the state of equilibrium
in the reheat plasma. We show that there is no ``thermal gravitino problem'' at
all within supersymmetry and we stress on a need of a new paradigm based on a
``quasi-thermal leptogenesis'', because in the bulk of the parameter space the
{\it old} thermal leptogenesis cannot account for the observed baryon
asymmetry.Comment: 53 pages. Final version published in JCA
Glioblastomas with primitive neuronal component harbor a distinct methylation and copy‑number profle with inactivation of TP53, PTEN, and RB1
Glioblastoma IDH-wildtype presents with a wide histological spectrum. Some features are so distinctive that they are considered as separate histological variants or patterns for the purpose of classification. However, these usually lack defined (epi-)genetic alterations or profiles correlating with this histology. Here, we describe a molecular subtype with overlap to the unique histological pattern of glioblastoma with primitive neuronal component. Our cohort consists of 63 IDH-wildtype glioblastomas that harbor a characteristic DNA methylation profile. Median age at diagnosis was 59.5 years. Copy-number variations and genetic sequencing revealed frequent alterations in TP53, RB1 and PTEN, with fewer gains of chromosome 7 and homozygous CDKN2A/B deletions than usually described for IDH-wildtype glioblastoma. Gains of chromosome 1 were detected in more than half of the cases. A poorly differentiated phenotype with frequent absence of GFAP expression, high proliferation index and strong staining for p53 and TTF1 often caused misleading histological classification as carcinoma metastasis or primitive neuroectodermal tumor. Clinically, many patients presented with leptomeningeal dissemination and spinal metastasis. Outcome was poor with a median overall survival of only 12 months. Overall, we describe a new molecular subtype of IDH-wildtype glioblastoma with a distinct histological appearance and genetic signature.publishedVersio
Scenarios of modulated perturbations
In an alternative mechanism recently proposed, adiabatic cosmological
perturbations are generated at the decay of the inflaton field due to small
fluctuations of its coupling to matter. This happens whenever the coupling is
governed by the vacuum expectation value of another field, which acquires
fluctuations during inflation. We discuss generalization and various possible
implementations of this mechansim, and present some specific particle physics
examples. In many cases the second field can start oscillating before
perturbations are imprinted, or survive long enough so to dominate over the
decay products of the inflaton. The primordial perturbations will then be
modified accordingly in each case.Comment: 12 pages, 3 figures. Final version to appear in Phys. Rev.
AI is a viable alternative to high throughput screening: a 318-target study
: High throughput screening (HTS) is routinely used to identify bioactive small molecules. This requires physical compounds, which limits coverage of accessible chemical space. Computational approaches combined with vast on-demand chemical libraries can access far greater chemical space, provided that the predictive accuracy is sufficient to identify useful molecules. Through the largest and most diverse virtual HTS campaign reported to date, comprising 318 individual projects, we demonstrate that our AtomNet® convolutional neural network successfully finds novel hits across every major therapeutic area and protein class. We address historical limitations of computational screening by demonstrating success for target proteins without known binders, high-quality X-ray crystal structures, or manual cherry-picking of compounds. We show that the molecules selected by the AtomNet® model are novel drug-like scaffolds rather than minor modifications to known bioactive compounds. Our empirical results suggest that computational methods can substantially replace HTS as the first step of small-molecule drug discovery