7,623 research outputs found
The Inert Doublet Model : a new archetype of WIMP dark matter?
The Inert Doublet Model (IDM) is a two doublet extension of the
Higgs-Brout-Englert sector of the Standard Model with a Z_2 symmetry in order
to prevent FCNC. If the Z_2 symmetry is not spontaneously broken, the lightest
neutral extra scalar is a dark matter candidate. We briefly review the
phenomenology of the model, emphasizing its relevance for the issue of
Electroweak Symmetry Breaking (EWSB) and the prospects for detection of dark
matter.Comment: Contribution the 10th International Conference on Topics in
Astroparticle and Underground Physics (TAUP 2007), Sendai, Japan, 11-15 Sep
200
Relating leptogenesis and dark matter
A scenario that relates the abundance of dark matter to the baryon asymmetry
of the Universe is presented. In this scenario, based on a left-right extension
of the Standard Model, dark matter is made of light, ~ 1 GeV, right-handed
Majorana neutrinos.Comment: 4 pages, 1 figure, to appear in the proceedings of 40th Rencontres de
Moriond, Electroweak Interactions and Unified Theories, March 11 - 18, 200
Masses of the Goldstone modes in the CFL phase of QCD at finite density
We construct the U_L(3) x U_R(3) effective lagrangian which encodes the
dynamics of the low energy pseudoscalar excitations in the Color-Flavor-Locking
superconducting phase of QCD at finite quark density. We include the effects of
instanton-induced interactions and study the mass pattern of the pseudoscalar
mesons. A tentative comparison with the analytical estimate for the gap
suggests that some of these low energy momentum modes are not stable for
moderate values of the quark chemical potential.Comment: 15 pages, 5 figures; Discussion of quark mass effects at very large
densities amended, references adde
Constraints on Light WIMP candidates from the Isotropic Diffuse Gamma-Ray Emission
Motivated by the measurements reported by direct detection experiments, most
notably DAMA, CDMS-II, CoGeNT and Xenon10/100, we study further the constraints
that might be set on some light dark matter candidates, M_DM ~ few GeV, using
the Fermi-LAT data on the isotropic gamma-ray diffuse emission. In particular,
we consider a Dirac fermion singlet interacting through a new Z' gauge boson,
and a scalar singlet S interacting through the Higgs portal. Both candidates
are WIMP (Weakly Interacting Massive Particles), i.e. they have an annihilation
cross-section in the pbarn range. Also they may both have a spin-independent
elastic cross section on nucleons in the range required by direct detection
experiments. Although being generic WIMP candidates, because they have
different interactions with Standard Model particles, their phenomenology
regarding the isotropic diffuse gamma-ray emission is quite distinct. In the
case of the scalar singlet, the one-to-one correspondence between its
annihilation cross-section and its spin-independent elastic scattering
cross-section permits to express the constraints from the Fermi-LAT data in the
direct detection exclusion plot, sigma_n^0--M_DM. Depending on the
astrophysics, we argue that it is possible to exclude the singlet scalar dark
matter candidate at 95 % CL. The constraints on the Dirac singlet interacting
through a Z' are comparatively weaker.Comment: 18 pages, 13 figures, replaced to match with the published versio
Confined hidden vector dark matter
We argue that the lightest vector bound states of a confining hidden sector
communicating with the Standard Model through the Higgs portal are stable and
are viable candidates of dark matter. The model is based on an SU(2) gauge
group with a scalar field in its fundamental representation and the stability
of the lightest vector bound state results from the existence of a custodial
symmetry. As the relic density depends essentially on the scale of confinement
in the hidden sector, Lambda_HS, agreement with WMAP abundance requires
Lambda_HS in the 20-120 TeV range.Comment: 6 page
Effective field theory approach to N=4 supersymmetric Yang-Mills at finite temperature
We study the perturbation expansion of the free energy of N=4 supersymmetric
SU(N) Yang-Mills at finite temperature in powers of 't Hooft's coupling g^2 N
in the large N limit. Infrared divergences are controlled by constructing a
hierarchy of two 3 dimensional effective field theories. This procedure is
applied to the calculation of the free energy to order (g^2 N)^(3/2), but it
can be extended to higher order corrections.Comment: LaTeX, 10 pages, 1 figure, uses eps
Instability of Non-Commutative SYM Theories at Finite Temperature
We extend our previous work on the quasi-particle excitations in N=4
non-commutative U(1) Yang-Mills theory at finite temperature. We show that
above some critical temperature there is a tachyon in the spectrum of
excitations. It is a collective transverse photon mode polarized in the
non-commutative plane. Thus the theory seems to undergo a phase transition at
high temperature. Furthermore we find that the group velocity of
quasi-particles generically exceeds the speed of light at low momentum.Comment: 23 pages (harvmac b-mode), 5 figures, v2: discussion on U(N) theories
and matter in fundamental representation added, misprints corrected,
references added v3: reference adde
Non-Primordial Solar Mass Black Holes
We propose a mechanism that can convert a sizeable fraction of neutron stars
into black holes with mass , too light to be produced via
standard stellar evolution. We show that asymmetric fermionic dark matter of
mass TeV, with attractive self-interaction within the range that
alleviates the problems of collisionless cold dark matter, can accumulate in a
neutron star and collapse, forming a seed black hole that converts the rest of
the star to a solar mass black hole. We estimate the fraction of neutron stars
that can become black holes without contradicting existing neutron star
observations. Like neutron stars, such solar mass black holes could be in
binary systems, which may be searched for by existing and forthcoming
gravitational wave detectors. The (non-)observation of binary mergers of solar
mass black holes may thus test the specific nature of the dark matter.Comment: 6 pages, 2 figure
Radion Assisted Gauge Inflation
We propose an extension to the recently proposed extranatural or gauge
inflation scenario in which the radius modulus field around which the Wilson
loop is wrapped assists inflation as it shrinks. We discuss how this might lead
to more generic initial conditions for inflation.Comment: 10 pages, 2 figure
Scalar Dark Matter Models with Significant Internal Bremsstrahlung
There has been interest recently on particle physics models that may give
rise to sharp gamma ray spectral features from dark matter annihilation.
Because dark matter is supposed to be electrically neutral, it is challenging
to build weakly interacting massive particle models that may accommodate both a
large cross section into gamma rays at, say, the Galactic center, and the right
dark matter abundance. In this work, we consider the gamma ray signatures of a
class of scalar dark matter models that interact with Standard Model dominantly
through heavy vector-like fermions (the vector-like portal). We focus on a real
scalar singlet S annihilating into lepton-antilepton pairs. Because this
two-body final-state annihilation channel is d-wave suppressed in the chiral
limit, we show that virtual internal bremsstrahlung emission of a gamma ray
gives a large correction, both today and at the time of freeze-out. For the
sake of comparison, we confront this scenario to the familiar case of a
Majorana singlet annihilating into light lepton-antilepton pairs, and show that
the virtual internal bremsstrahlung signal may be enhanced by a factor of (up
to) two orders of magnitude. We discuss the scope and possible generalizations
of the model.Comment: 25 pages, 10 figures, typos corrected, added references, matching
version accepted by JCA
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