15,142 research outputs found
Categorisation and Detection of Dark Matter Candidates from String/M-theory Hidden Sectors
We study well-motivated dark matter candidates arising from weakly-coupled
hidden sectors in compactified string/-theory. Imposing generic top-down
constraints greatly restricts allowed candidates. By considering the possible
mechanisms for achieving the correct dark matter relic density, we compile
categories of viable dark matter candidates and annihilation mediators. We
consider the case where supersymmetry breaking occurs via moduli stabilisation
and is gravitationally mediated to the visible and other hidden sectors,
without assuming sequestering of the sector in which supersymmetry is broken.
We find that in this case, weakly-coupled hidden sectors only allow for
fermionic dark matter. Additionally, most of the mechanisms for obtaining the
full relic density only allow for a gauge boson mediator, such as a dark .
Given these considerations, we study the potential for discovering or
constraining the allowed parameter space given current and future direct
detection experiments, and direct production at the LHC. We also present a
model of a hidden sector which would contain a satisfactory dark matter
candidate.Comment: 29 pages, 10 figure
Nuclei Near and Far From β-Stability Line
Proton to neutron ratio around β-stability line presents an open challenge to the nuclear physicists. The prominent milestone in this regard is the discovery of the super heavy elements, nuclear halos in the lightest neutron-rich nuclei, experimental mapping of the nuclear shell structure near and far from stability. In this present paper, the behavior of the p- and n- halo nuclei near the β-stability line are discussed considering the variation of radius with respect to the mass number and N~Z for different nuclei. Our aim is to study the nuclear properties through neutron and proton skin. The isospin symmetry breaking is for heavy halo nuclei of strong interest
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Metagenomic deep sequencing of aqueous fluid detects intraocular lymphomas.
IntroductionCurrently, the detection of pathogens or mutations associated with intraocular lymphomas heavily relies on prespecified, directed PCRs. With metagenomic deep sequencing (MDS), an unbiased high-throughput sequencing approach, all pathogens as well as all mutations present in the host's genome can be detected in the same small amount of ocular fluid.MethodsIn this cross-sectional case series, aqueous fluid samples from two patients were submitted to MDS to identify pathogens as well as common and rare cancer mutations.ResultsMDS of aqueous fluid from the first patient with vitreal lymphoma revealed the presence of both Epstein-Barr virus (HHV-4/EBV) and human herpes virus 8 (HHV-8) RNA. Aqueous fluid from the second patient with intraocular B-cell lymphoma demonstrated a less common mutation in the MYD88 gene associated with B-cell lymphoma.ConclusionMDS detects pathogens that, in some instances, may drive the development of intraocular lymphomas. Moreover, MDS is able to identify both common and rare mutations associated with lymphomas
No Eigenvalue in Finite Quantum Electrodynamics
We re-examine Quantum Electrodynamics (QED) with massless electron as a
finite quantum field theory as advocated by Gell-Mann-Low, Baker-Johnson,
Adler, Jackiw and others. We analyze the Dyson-Schwinger equation satisfied by
the massless electron in finite QED and conclude that the theory admits no
nontrivial eigenvalue for the fine structure constant.Comment: 13 pages, Late
Phase Transition and Hybrid Star in a Nonlinear model
The phase transition between the nuclear matter and the quark matter is
examined. The relativistic mean field theory(RMF) is consider with interacting
nucleons and mesons using TM1 parameter set for the nuclear matter equations of
state. It is found that the trasition point depends on coupling constant
and bag pressure. From the study of the structure of a hybrid
neutron star, it is observed that the star contains quark matter in the
interior and neutron matter on the outer perifery.Comment: 8 pages, 7 figures, to appear in Int. J. Mod. Phy.
Separation energies of light nuclei with atomic number from 1 to 20
The 1n and 1p halo nuclei from atomic number 1 to 20 are discussed here to calculate the variation of separation energy with mass defect and binding energy. Semi-empirical mass formula and shell model are the methods applied here. The appearances of p- and r-branches satisfying the selection rules for different isotopes of nuclides are discussed
Testing Conditional Independence of Discrete Distributions
We study the problem of testing \emph{conditional independence} for discrete
distributions. Specifically, given samples from a discrete random variable on domain , we want to distinguish,
with probability at least , between the case that and are
conditionally independent given from the case that is
-far, in -distance, from every distribution that has this
property. Conditional independence is a concept of central importance in
probability and statistics with a range of applications in various scientific
domains. As such, the statistical task of testing conditional independence has
been extensively studied in various forms within the statistics and
econometrics communities for nearly a century. Perhaps surprisingly, this
problem has not been previously considered in the framework of distribution
property testing and in particular no tester with sublinear sample complexity
is known, even for the important special case that the domains of and
are binary.
The main algorithmic result of this work is the first conditional
independence tester with {\em sublinear} sample complexity for discrete
distributions over . To complement our upper
bounds, we prove information-theoretic lower bounds establishing that the
sample complexity of our algorithm is optimal, up to constant factors, for a
number of settings. Specifically, for the prototypical setting when , we show that the sample complexity of testing conditional
independence (upper bound and matching lower bound) is
\[
\Theta\left({\max\left(n^{1/2}/\epsilon^2,\min\left(n^{7/8}/\epsilon,n^{6/7}/\epsilon^{8/7}\right)\right)}\right)\,.
\
Scherk-Schwarz reduction of M-theory on G2-manifolds with fluxes
We analyse the 4-dimensional effective supergravity theories obtained from
the Scherk--Schwarz reduction of M-theory on twisted 7-tori in the presence of
4-form fluxes. We implement the appropriate orbifold projection that preserves
a G2-structure on the internal 7-manifold and truncates the effective field
theory to an N=1, D=4 supergravity. We provide a detailed account of the
effective supergravity with explicit expressions for the Kaehler potential and
the superpotential in terms of the fluxes and of the geometrical data of the
internal manifold. Subsequently, we explore the landscape of vacua of M-theory
compactifications on twisted tori, where we emphasize the role of geometric
fluxes and discuss the validity of the bottom-up approach. Finally, by reducing
along isometries of the internal 7-manifold, we obtain superpotentials for the
corresponding type IIA backgrounds.Comment: 43 pages, Latex; v3 typos corrected, one reference added, JHEP
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