675 research outputs found
Simplified Models for Dark Matter Interacting with Quarks
We investigate simplified models in which dark matter particles, taken to be
either Dirac or Majorana fermions, couple to quarks via colored mediators. We
determine bounds from colliders and direct detection experiments, and show how
the interplay of the two leads to a complementary view of this class of dark
matter models. Forecasts for future searches in light of the current
constraints are presented.Comment: 12 pages, 13 figures (39 images) Fixed erroneous calculation and
updated plot
Numerical Investigations of Oscillons in 2 Dimensions
Oscillons, extremely long-living localized oscillations of a scalar field,
are studied in theories with quartic and sine-Gordon potentials in two spatial
dimensions. We present qualitative results concentrating largely on a study in
frequency space via Fourier analysis of oscillations. Oscillations take place
at a fundamental frequency just below the threshold for the production of
radiation, with exponentially suppressed harmonics. The time evolution of the
oscillation frequency points indirectly to a life time of at least 10 million
oscillations. We study also elliptical perturbations of the oscillon, which are
shown to decay. We finish by presenting results for boosted and collided
oscillons, which point to a surprising persistence and soliton-like behaviour.Comment: Matches the published version (12 pages, 34 figures
Some stationary properties of a -ball in arbitrary space dimensions
Introducing new physically motivated ans\"{a}tze, we explore both
analytically and numerically the classical and absolute stabilities of a single
-ball in an arbitrary number of spatial dimensions , working in both the
thin and thick wall limits.Comment: 35 pages, 32 figures; added references, corrected typo
Numerical Simulation of an Electroweak Oscillon
Numerical simulations of the bosonic sector of the
electroweak Standard Model in 3+1 dimensions have demonstrated the existence of
an oscillon -- an extremely long-lived, localized, oscillatory solution to the
equations of motion -- when the Higgs mass is equal to twice the boson
mass. It contains total energy roughly 30 TeV localized in a region of radius
0.05 fm. A detailed description of these numerical results is presented.Comment: 12 pages, 8 figures, uses RevTeX4; v2: expanded results section,
fixed typo
Special Conformal Symmetry of Worldvolume Actions
Kappa-symmetric worldvolume actions of the D3-, M5- and M2-branes can be
coupled consistently to their near horizon bosonic geometry background. We
study the gauge-fixed action in the approximation in which only the transverse
radial direction of the brane is allowed to fluctuate. The generalized special
conformal symmetry of these self-interacting actions is established. This opens
up a possibility to find out if the full superconformal symmetry of the free
actions of these branes survives in the presence of coupling defined by the
size of the anti-deSitter throat.Comment: 5 pages, late
Perturbation theory for localized solutions of sine-Gordon equation: decay of a breather and pinning by microresistor
We develop a perturbation theory that describes bound states of solitons
localized in a confined area. External forces and influence of inhomogeneities
are taken into account as perturbations to exact solutions of the sine-Gordon
equation. We have investigated two special cases of fluxon trapped by a
microresistor and decay of a breather under dissipation. Also, we have carried
out numerical simulations with dissipative sine-Gordon equation and made
comparison with the McLaughlin-Scott theory. Significant distinction between
the McLaughlin-Scott calculation for a breather decay and our numerical result
indicates that the history dependence of the breather evolution can not be
neglected even for small damping parameter
On decay of large amplitude bubble of disoriented chiral condensate
The time evolution of initially formed large amplitude bubble of disoriented
chiral condensate (DCC) is studied. It is found that the evolution of this
object may have a relatively long pre-decay stage. Simple explanation of such
delay of the DCC bubble decay is given. This delay is related to the existence
of the approximate solutions of multi-soliton type of the corresponding radial
sine-Gordon equation in (3+1) dimensions at large bubble radius.Comment: 6 pages, LaTeX, 5 PostScript figure
NMR linewidth and Skyrmion localization in quantum Hall ferromagnets
The non-monotonic behavior of the NMR signal linewidth in the 2D quantum Hall
system is explained in terms of the interplay between skyrmions localization,
due to the influence of disorder, and the non-trivial temperature dependent
skyrmion dynamics.Comment: 5 pages, 2 figure
Half-skyrmion picture of single hole doped CuO_2 plane
Based on the Zhang-Rice singlet picture, it is argued that the half-skyrmion
is created by the doped hole in the single hole doped high-T_c cuprates with
N'eel ordering. The spin configuration around the Zhang-Rice singlet, which has
the form of superposition of the two different d-orbital hole spin states, is
studied within the non-linear \sigma model and the CP^1 model. The spin
configurations associated with each hole spin state are obtained, and we find
that the superposition of these spin configuration turns out to be the
half-skyrmion that is characterized by a half of the topological charge. The
excitation spectrum of the half-skyrmion is obtained by making use of Lorentz
invariance of the effective theory and is qualitatively in good agreement with
angle resolved photoemission spectroscopy on the parent compunds. Estimated
values of the parameters contained in the excitation spectrum are in good
agreement with experimentally obtained values. The half-skyrmion theory
suggests a picture for the difference between the hole doped compounds and the
electron doped compounds.Comment: 13 pages, 2 figures, to be published in Phys. Rev.
Fate of the false monopoles: induced vacuum decay
We study a gauge theory model where there is an intermediate symmetry
breaking to a meta- stable vacuum that breaks a simple gauge group to a U (1)
factor. Such models admit the existence of meta-stable magnetic monopoles,
which we dub false monopoles. We prove the existence of these monopoles in the
thin wall approximation. We determine the instantons for the collective
coordinate that corresponds to the radius of the monopole wall and we calculate
the semi-classical tunneling rate for the decay of these monopoles. The
monopole decay consequently triggers the decay of the false vacuum. As the
monopole mass is increased, we find an enhanced rate of decay of the false
vacuum relative to the celebrated homogeneous tunneling rate due to Coleman
[1].Comment: 10 pages, 4 figure
- …