583 research outputs found
A Statistical Analysis of Supersymmetric Dark Matter in the MSSM after WMAP
We study supersymmetric dark matter in the general flavor diagonal MSSM by
means of an extensive random scan of its parameter space. We find that, in
contrast with the standard mSUGRA lore, the large majority of viable models
features either a higgsino or a wino-like lightest neutralino, and yields a
relic abundance well below the WMAP bound. Among the models with neutralino
relic density within the WMAP range, higgsino-like neutralinos are still
dominant, though a sizeable fraction of binos is also present. In this latter
case, relic density suppression mechanisms are shown to be essential in order
to obtain the correct neutralino abundance. We then carry out a statistical
analysis and a general discussion of neutralino dark matter direct detection
and of indirect neutralino detection at neutrino telescopes and at antimatter
search experiments. We point out that current data exclude only a marginal
portion of the viable parameter space, and that models whose thermal relic
abundance lies in the WMAP range will be significantly probed only at future
direct detection experiments. Finally, we emphasize the importance of relic
density enhancement mechanisms for indirect detection perspectives, in
particular at future antimatter search experiments.Comment: 39 pages, 25 figure
Twisted Eguchi-Kawai Reduced Chiral Models
We study the twisted Eguchi-Kawai (TEK) reduction procedure for large-N
unitary matrix lattice models. In particular, we consider the case of
two-dimensional principal chiral models, and use numerical Monte Carlo (MC)
simulations to check the conjectured equivalence of TEK reduced model and
standard lattice model in the large-N limit. The MC results are compared with
the large-N limit of lattice principal chiral models to verify the supposed
equivalence. The consistency of the TEK reduction procedure is verified in the
strong-coupling region, i.e. for where is the
location of the large-N phase transition. On the other hand, in the
weak-coupling regime , relevant for the continuum limit, our MC
results do not support the equivalence of the large-N limits of the lattice
chiral model and the corresponding TEK reduction. The implications for the
correspondence between TEK model and noncommutative field theory are also
discussed.Comment: 16 page
Detecting dark matter WIMPs in the Draco dwarf: a multi-wavelength perspective
We explore the possible signatures of dark matter (DM) pair annihilations in
the nearby dwarf spheroidal galaxy Draco. After investigating the mass models
for Draco in the light of available observational data, we carefully model the
DM density profile, taking advantage of numerical simulations of hierarchical
structure formation. We then analyze the gamma-ray and electron/positron yield
expected for weakly interacting DM particle (WIMP) models, including an
accurate treatment of the propagation of the charged particle species. We show
that unlike in larger DM structures - such as galaxy clusters - spatial
diffusion plays here an important role. While Draco would appear as a
point-like gamma-ray source, synchrotron emission from electrons and positrons
produced by WIMP annihilations features a spatially extended structure.
Depending upon the cosmic ray propagation setup and the size of the magnetic
fields, the search for a diffuse radio emission from Draco can be a more
sensitive indirect DM search probe than gamma rays. Finally, we show that
available data are consistent with the presence of a black hole at the center
of Draco: if this is indeed the case, very significant enhancements of the
rates for gamma rays and other emissions related to DM annihilations are
expected.Comment: 25 pages, 21 figures, submitted to Phys. Rev.
Dendroecology of Gymnanthes klotzschiana Müll. Arg. trees, naturally growing in Northern Uruguay.
Ameridendro
A 331 WIMPy Dark Radiation Model
Recent observations suggest that the number of relativistic degrees of
freedom in the early universe might exceed what is predicted in the standard
cosmological model. If even a small, percent-level fraction of dark matter
particles are produced relativistically, they could mimic the effect of an
extra realistic species at matter-radiation equality while obeying BBN, CMB and
Structure Formation bounds. We show that this scenario is quite naturally
realized with a weak-scale dark matter particle and a high-scale ``mother''
particle within a well motivated 3-3-1 gauge model, which is particularly
interesting for being consistent with electroweak precision measurements, with
recent LHC results, and for offering a convincing explanation for the number of
generations in the Standard Model.Comment: 10 pages,7 figures. Matches Published EPJC versio
Low energy antideuterons: shedding light on dark matter
Low energy antideuterons suffer a very low secondary and tertiary
astrophysical background, while they can be abundantly synthesized in dark
matter pair annihilations, therefore providing a privileged indirect dark
matter detection technique. The recent publication of the first upper limit on
the low energy antideuteron flux by the BESS collaboration, a new evaluation of
the standard astrophysical background, and remarkable progresses in the
development of a dedicated experiment, GAPS, motivate a new and accurate
analysis of the antideuteron flux expected in particle dark matter models. To
this extent, we consider here supersymmetric, universal extra-dimensions (UED)
Kaluza-Klein and warped extra-dimensional dark matter models, and assess both
the prospects for antideuteron detection as well as the various related sources
of uncertainties. The GAPS experiment, even in a preliminary balloon-borne
setup, will explore many supersymmetric configurations, and, eventually, in its
final space-borne configuration, will be sensitive to primary antideuterons
over the whole cosmologically allowed UED parameter space, providing a search
technique which is highly complementary with other direct and indirect dark
matter detection experiments.Comment: 26 pages, 7 figures; version to appear in JCA
Electron-electron interactions in decoupled graphene layers
Multi-layer graphene on the carbon face of silicon carbide is an intriguing
electronic system which typically consists of a stack of ten or more layers.
Rotational stacking faults in this system dramatically reduce inter-layer
coherence. In this article we report on the influence of inter-layer
interactions, which remain strong even when coherence is negligible, on the
Fermi liquid properties of charged graphene layers. We find that inter-layer
interactions increase the magnitudes of correlation energies and decrease
quasiparticle velocities, even when remote-layer carrier densities are small,
and that they lessen the influence of exchange and correlation on the
distribution of carriers across layers.Comment: 8 pages, 4 figures, submitte
Increasing the Neutralino Relic Abundance with Slepton Coannihilations: Consequences for Indirect Dark Matter Detection
We point out that if the lightest supersymmetric particle (LSP) is a
Higgsino- or Wino-like neutralino, the net effect of coannihilations with
sleptons is to increase the relic abundance, rather than producing the usual
suppression, which takes place if the LSP is Bino-like. The reason for the
enhancement lies in the effective thermally averaged cross section at
freeze-out: sleptons annihilate (and co-annihilate) less efficiently than the
neutralino(s)-chargino system, therefore slepton coannihilations effectively
act as parasite degrees of freedom at freeze-out. Henceforth, the thermal relic
abundance of LSP's corresponds to the cold Dark Matter abundance for smaller
values of the LSP mass, and larger values of the neutralino pair annihilation
cross section. In turn, at a given thermal neutralino relic abundance, this
implies larger indirect detection rates, as a result of an increase in the
fluxes of antimatter, gamma rays and neutrinos from the Sun orginating from
neutralino pair annihilations.Comment: 16 pages, 6 figures, references added, typos corrected, matches with
the published versio
Baryogenesis, Electric Dipole Moments and Dark Matter in the MSSM
We study the implications for electroweak baryogenesis (EWB) within the
minimal supersymmetric Standard Model (MSSM) of present and future searches for
the permanent electric dipole moment (EDM) of the electron, for neutralino dark
matter, and for supersymmetric particles at high energy colliders. We show that
there exist regions of the MSSM parameter space that are consistent with both
present two-loop EDM limits and the relic density and that allow for successful
EWB through resonant chargino and neutralino processes at the electroweak phase
transition. We also show that under certain conditions the lightest neutralino
may be simultaneously responsible for both the baryon asymmetry and relic
density. We give present constraints on chargino/neutralino-induced EWB implied
by the flux of energetic neutrinos from the Sun, the prospective constraints
from future neutrino telescopes and ton-sized direct detection experiments, and
the possible signatures at the Large Hadron Collider and International Linear
Collider.Comment: 32 pages, 10 figures; version to appear on JHE
A Perspective on Nrf2 Signaling Pathway for Neuroinflammation: A Potential Therapeutic Target in Alzheimer's and Parkinson's Diseases
Neuroinflammation plays a pivotal role in Alzheimer's disease (AD) and Parkinson's disease (PD), the leading causes of dementia. These neurological disorders are characterized by the accumulation of misfolded proteins such as amyloid-ß (Aß), tau protein and α-synuclein, contributing to mitochondrial fragmentation, oxidative stress, and neuroinflammation. Misfolded proteins activate microglia, which induces neuroinflammation, expression of pro-inflammatory cytokines and subsequently facilitates synaptic damage and neuronal loss. So far, all the proposed drugs were based on the inhibition of protein aggregation and were failed in clinical trials. Therefore, the treatment options of dementia are still a challenging issue. Thus, it is worthwhile to study alternative therapeutic strategies. In this context, there is increasing data on the pivotal role of transcription factor NF- E2 p45-related factor 2 (Nrf2) on the redox homeostasis and anti-inflammatory functions in neurodegenerative disorders. Interestingly, Nrf2 signaling pathway has shown upregulation of antioxidant genes, inhibition of microglia-mediated inflammation, and improved mitochondrial function in neurodegenerative diseases, suggesting Nrf2 activation could be a novel therapeutic approach to target pathogenesis. The present review will examine the correlation between Nrf2 signaling with neuroinflammation in AD and PD
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