652 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
Assisted freeze-out
We explore a class of dark matter models with two dark matter candidates,
only one interacts with the standard model sector. One of the dark matter is
thermalized with the assistance of the other stable particle. While both stable
particles contribute to the total relic density only one can elastically
scatter with nuclei, thus effectively reducing the direct detection rate.Comment: 16 pages, 13 figures, minor corrections, the final version published
in JCA
The impact of market orientation on research-based spin off performance: emerging issues from an exploratory study
The paper addresses the relationship between Market Orientation (MO) and Research based spin offs' business performance, using a sample of 90 Italian RBSOs present in the Netval (Italian association for the valorisation of results from public research) database. The findings of the study may be useful for researchers and academics, advancing knowledge on Research based spin-offs (RBSOs) and the impact of MO on their performance, but also professionals from new high tech ventures and technology transfer offices may use these results to plan and design market-focused actions and support activities that will lead to improved business performance.The results could in fact indicate to entrepreneurs (or the entrepreneurial team) of this kind of firms which dimensions of MO deserve more attention in order to obtain a higher business performance
Local Group dSph radio survey with ATCA (III): Constraints on Particle Dark Matter
We performed a deep search for radio synchrotron emissions induced by weakly
interacting massive particles (WIMPs) annihilation or decay in six dwarf
spheroidal (dSph) galaxies of the Local Group. Observations were conducted with
the Australia Telescope Compact Array (ATCA) at 16 cm wavelength, with an rms
sensitivity better than 0.05 mJy/beam in each field. In this work, we first
discuss the uncertainties associated with the modeling of the expected signal,
such as the shape of the dark matter (DM) profile and the dSph magnetic
properties. We then investigate the possibility that point-sources detected in
the proximity of the dSph optical center might be due to the emission from a DM
cuspy profile. No evidence for an extended emission over a size of few arcmin
(which is the DM halo size) has been detected. We present the associated bounds
on the WIMP parameter space for different annihilation/decay final states and
for different astrophysical assumptions. If the confinement of electrons and
positrons in the dSph is such that the majority of their power is radiated
within the dSph region, we obtain constraints on the WIMP annihilation rate
which are well below the thermal value for masses up to few TeV. On the other
hand, for conservative assumptions on the dSph magnetic properties, the bounds
can be dramatically relaxed. We show however that, within the next 10 years and
regardless of the astrophysical assumptions, it will be possible to
progressively close in on the full parameter space of WIMPs by searching for
radio signals in dSphs with SKA and its precursors.Comment: 17 pages, 6 figure panels. Companion papers: arXiv:1407.5479 and
arXiv:1407.5482. v3: minor revision, matches published versio
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
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
The Effects of Dark Matter Decay and Annihilation on the High-Redshift 21 cm Background
The radiation background produced by the 21 cm spin-flip transition of
neutral hydrogen at high redshifts can be a pristine probe of fundamental
physics and cosmology. At z~30-300, the intergalactic medium (IGM) is visible
in 21 cm absorption against the cosmic microwave background (CMB), with a
strength that depends on the thermal (and ionization) history of the IGM. Here
we examine the constraints this background can place on dark matter decay and
annihilation, which could heat and ionize the IGM through the production of
high-energy particles. Using a simple model for dark matter decay, we show
that, if the decay energy is immediately injected into the IGM, the 21 cm
background can detect energy injection rates >10^{-24} eV cm^{-3} sec^{-1}. If
all the dark matter is subject to decay, this allows us to constrain dark
matter lifetimes <10^{27} sec. Such energy injection rates are much smaller
than those typically probed by the CMB power spectra. The expected brightness
temperature fluctuations at z~50 are a fraction of a mK and can vary from the
standard calculation by up to an order of magnitude, although the difference
can be significantly smaller if some of the decay products free stream to lower
redshifts. For self-annihilating dark matter, the fluctuation amplitude can
differ by a factor <2 from the standard calculation at z~50. Note also that, in
contrast to the CMB, the 21 cm probe is sensitive to both the ionization
fraction and the IGM temperature, in principle allowing better constraints on
the decay process and heating history. We also show that strong IGM heating and
ionization can lead to an enhanced H_2 abundance, which may affect the earliest
generations of stars and galaxies.Comment: submitted to Phys Rev D, 14 pages, 8 figure
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
Quintessence, inflation and baryogenesis from a single pseudo-Nambu-Goldstone boson
We exhibit a model in which a single pseudo-Nambu-Goldstone boson explains
dark energy, inflation and baryogenesis. The model predicts correlated signals
in future collider experiments, WIMP searches, proton decay experiments, dark
energy probes, and the PLANCK satellite CMB measurements.Comment: 16 pages, 3 color figure
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
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