4,963 research outputs found
Re-derived overclosure bound for the inert doublet model
We apply a formalism accounting for thermal effects (such as modified
Sommerfeld effect; Salpeter correction; decohering scatterings; dissociation of
bound states), to one of the simplest WIMP-like dark matter models, associated
with an "inert" Higgs doublet. A broad temperature range T ~ M/20...M/10^4 is
considered, stressing the importance and less-understood nature of late
annihilation stages. Even though only weak interactions play a role, we find
that resummed real and virtual corrections increase the tree-level overclosure
bound by 1...18%, depending on quartic couplings and mass splittings.Comment: 29 pages. v2: clarifications added, published versio
Mesonic screening masses at high temperature and finite density
We compute the first perturbative correction to the static correlation
lengths of light quark bilinears in hot QCD with finite quark chemical
potentials. The correction is small and positive, with mu-dependence depending
on the relative sign of chemical potentials and the number of dynamical
flavors. The computation is carried out using a three-dimensional effective
theory for the lowest fermionic Matsubara mode. We also compute the full
correlator in free theory and find a rather complicated general mu-dependence
at shorter distances. Finally, rough comparisons with lattice simulations are
discussed.Comment: 24 pages, 5 figures, JHEP style. Minor corrections and
clarifications, version to appear in JHE
Lack of Interaction between the Dust Grains and the Anomalous Radio Jet in the Nearby Spiral Galaxy NGC 4258
We obtained Spitzer/IRAC 3.6-8 micron images of the nearby spiral galaxy NGC
4258 to study possible interactions between dust and the radio jet. In our
analysis we also included high-resolution radio continuum, H-alpha, CO, and
X-ray data. Our data reveal that the 8 micron emission, believed to originate
largely from PAH molecules and hot dust, is an excellent tracer of the normal
spiral structure in NGC 4258, and hence it originates from the galactic plane.
We investigated the possibility of dust destruction by the radio jet by
calculating correlation coefficients between the 8 micron and radio continuum
emissions along the jet in two independent ways, namely (i) from
wavelet-transformed maps of the original images at different spatial scales,
and (ii) from one-dimensional intensity cuts perpendicular to the projected
path of the radio jet on the sky. No definitive sign of a correlation (or
anticorrelation) was detected on relevant spatial scales with either approach,
implying that any dust destruction must take place at spatial scales that are
not resolved by our observations.Comment: Accepted for publication in the Astronomical Journal (11 pages, 10
figures, 1 table
CO Distribution and Kinematics Along the Bar in the Strongly Barred Spiral NGC 7479
We report on the 2.5 arcsec (400 pc) resolution CO (J = 1 -> 0) observations
covering the whole length of the bar in the strongly barred late-type spiral
galaxy NGC 7479. CO emission is detected only along a dust lane that traverses
the whole length of the bar, including the nucleus. The emission is strongest
in the nucleus. The distribution of emission is clumpy along the bar outside
the nucleus, and consists of gas complexes that are unlikely to be
gravitationally bound. The CO kinematics within the bar consist of two separate
components. A kinematically distinct circumnuclear disk, < 500 pc in diameter,
is undergoing predominantly circular motion with a maximum rotational velocity
of 245 km/s at a radius of 1 arcsec (160 pc). The CO-emitting gas in the bar
outside the circumnuclear disk has substantial noncircular motions which are
consistent with a large radial velocity component, directed inwards. The CO
emission has a large velocity gradient across the bar dust lane, ranging from
0.5 to 1.9 km/s/pc after correcting for inclination, and the projected velocity
change across the dust lane is as high as 200 km/s. This sharp velocity
gradient is consistent with a shock front at the location of the bar dust lane.
A comparison of H-alpha and CO kinematics across the dust lane shows that
although the H-alpha emission is often observed both upstream and downstream
from the dust lane, the CO emission is observed only where the velocity
gradient is large. We also compare the observations with hydrodynamic models
and discuss star formation along the bar.Comment: 16 pages, including 10 figures. Accepted for publication in Ap
Debye mass from domainwalls and dimensionally reduced phase diagram
To measure the Debye mass in dimensionally reduced QCD for we
replace in the correlator of two Polyakov loops one of the loops by a wall
triggered by a dimensionally reduced twist. The phase diagram for has
R-parity broken in part of the Higgs phase.Comment: LATTICE98(hightemp
Thermal dark matter co-annihilating with a strongly interacting scalar
Recently many investigations have considered Majorana dark matter
co-annihilating with bound states formed by a strongly interacting scalar
field. However only the gluon radiation contribution to bound state formation
and dissociation, which at high temperatures is subleading to soft 2->2
scatterings, has been included. Making use of a non-relativistic effective
theory framework and solving a plasma-modified Schrodinger equation, we address
the effect of soft 2->2 scatterings as well as the thermal dissociation of
bound states. We argue that the mass splitting between the Majorana and scalar
field has in general both a lower and an upper bound, and that the dark matter
mass scale can be pushed at least up to 5...6 TeV.Comment: 19 pages. v2: clarifications added, published versio
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