664 research outputs found
Matrix Models of Noncommutative (2d+1) Lattice Gauge Theories
We investigate the problem of mapping, through the Morita equivalence, odd
dimensional noncommutative lattice gauge theories onto suitable matrix models.
We specialize our analysis to noncommutative three dimensional QED (NCQED) and
scalar QED (NCSQED), for which we explicitly build the corresponding Matrix
Model.Comment: 13 pages, LaTeX, no Figure
Supersymmetric Contributions to Weak Decay Correlation Coefficients
We study supersymmetric contributions to correlation coefficients that
characterize the spectral shape and angular distribution for polarized muon-
and beta-decays. In the minimal supersymmetric Standard Model (MSSM), one-loop
box graphs containing superpartners can give rise to non-(V-A)x(V-A) four
fermion operators in the presence of left-right or flavor mixing between
sfermions. We analyze the present phenomenological constraints on such mixing
and determine the range of allowed contributions to the weak decay correlation
coefficients. We discuss the prospective implications for future muon- and
beta-decay experiments, and argue that they may provide unique probes of
left-right mixing in the first generation scalar fermion sector.Comment: Revised version - to appear in Phys.Rev.
Dendroecology of Gymnanthes klotzschiana Müll. Arg. trees, naturally growing in Northern Uruguay.
Ameridendro
Astrophysical limitations to the identification of dark matter: indirect neutrino signals vis-a-vis direct detection recoil rates
A convincing identification of dark matter (DM) particles can probably be
achieved only through a combined analysis of different detections strategies,
which provides an effective way of removing degeneracies in the parameter space
of DM models. In practice, however, this program is made complicated by the
fact that different strategies depend on different physical quantities, or on
the same quantities but in a different way, making the treatment of systematic
errors rather tricky. We discuss here the uncertainties on the recoil rate in
direct detection experiments and on the muon rate induced by neutrinos from
dark matter annihilations in the Sun, and we show that, contrarily to the local
DM density or overall cross section scale, irreducible astrophysical
uncertainties affect the two rates in a different fashion, therefore limiting
our ability to reconstruct the parameters of the dark matter particle. By
varying within their respective errors astrophysical parameters such as the
escape velocity and the velocity dispersion of dark matter particles, we show
that the uncertainty on the relative strength of the neutrino and
direct-detection signal is as large as a factor of two for typical values of
the parameters, but can be even larger in some circumstances.Comment: 12 pages, 3 figures. Improved presentation and Fig.3; clarifications,
references and an appendix added; conclusions unchanged. Matches version
published in PR
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
Right-handed Neutrino Dark Matter, Neutrino Masses, and non-Standard Cosmology in a 2HDM
We explore the dark matter phenomenology of a weak-scale right-handed
neutrino in the context of a Two Higgs Doublet Model. The expected signal at
direct detection experiments is different from the usual spin-independent and
spin-dependent classification since the scattering with quarks depends on the
dark matter spin. The dark matter relic density is set by thermal freeze-out
and in the presence of non-standard cosmology, where an Abelian gauge symmetry
is key for the dark matter production mechanism. We show that such symmetry
allows us to simultaneously address neutrino masses and the flavor problem
present in general Two Higgs Doublet Model constructions. Lastly, we outline
the region of parameter space that obeys collider, perturbative unitarity and
direct detection constraints.Comment: 27 pages, 3 figures. Matches the version accepted for publication in
JCA
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
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
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
- …