44,785 research outputs found

### Dilaton as a Dark Matter Candidate and its Detection

Assuming that the dilaton is the dark matter of the universe, we propose an
experiment to detect the relic dilaton using the electromagnetic resonant
cavity, based on the dilaton-photon conversion in strong electromagnetic
background. We calculate the density of the relic dilaton, and estimate the
dilaton mass for which the dilaton becomes the dark matter of the universe.
With this we calculate the dilaton detection power in the resonant cavity, and
compare it with the axion detection power in similar resonant cavity
experiment.Comment: 23 pages, 2 figure

### Kinetically-controlled thin-film growth of layered $\beta$- and $\gamma-$Na$_{x}$CoO$_{2}$ cobaltate

We report growth characteristics of epitaxial $\beta$-Na$_{0.6}$CoO$_{2}$ and
$\gamma$-Na$_{0.7}$CoO$_{2}$ thin films on (001) sapphire substrates grown by
pulsed-laser deposition. Reduction of deposition rate could change structure of
Na$_{x}$CoO$_{2}$ thin film from $\beta$-phase with island growth mode to
$\gamma$-phase with layer-by-layer growth mode. The
$\gamma$-Na$_{0.7}$CoO$_{2}$ thin film exhibits spiral surface growth with
multiterraced islands and highly crystallized texture compared to that of the
$\beta$-Na$_{0.6}$CoO$_{2}$ thin film. This heterogeneous epitaxial film growth
can give opportunity of strain effect of physical properties and growth
dynamics of Na$_{x}$CoO$_{2}$ as well as subtle nature of structural change.Comment: accepted for publication in Applied Physics Letter

### High-frequency sound propagation in a spatially varying mean flow

An equation for acoustic ray paths in a spatially varying mean flow was examined to determine some of the characteristics of the flow gradient effects on sound propagation. In a potential flow, the acoustic rays are deflected in the direction of increasing mean flow, and the gradient of the mean flow speed is the dominant factor causing the ray deflection. In contrast, in a sheared mean flow, the vorticity is the dominant factor in deflection of the acoustic rays

### Gravitationally Coupled Electroweak Monopole

We present a family of gravitationally coupled electroweak monopole solutions
in Einstein-Weinberg-Salam theory. Our result confirms the existence of
globally regular gravitating electroweak monopole which changes to the
magnetically charged black hole as the Higgs vacuum value approaches to the
Planck scale. Moreover, our solutions could provide a more accurate description
of the monopole stars and magnetically charged black holes

### Finite Energy Electroweak Dyon

The recent MoEDAL experiment at LHC to detect the electroweak monopole makes
the theoretical prediction of the monopole mass an urgent issue. We discuss
different ways to estimate the mass of the electroweak monopole. We first
present a scaling argument which indicates that the mass of the electroweak
monopole to be around 4 TeV. To justify this we construct finite energy
analytic dyon solutions which could be viewed as the regularized Cho-Maison
dyon, modifying the coupling strengths of the electromagnetic interaction of
$W$-boson in the standard model. Our result demonstrates that a genuine
electroweak monopole whose mass scale is much smaller than the grand
unification scale can exist, which can actually be detected at the present LHC.Comment: arXiv admin note: substantial text overlap with arXiv:hep-th/0210299,
arXiv:hep-th/970703

### Comment on $D_s^* \to D_s \pi^0$ Decay

We calculate the rate for $D_s^* \rightarrow D_s \pi^0$ decay using Chiral
Perturbation Theory. This isospin violating process results from $\pi^0$ -
$\eta$ mixing, and its amplitude is proportional to $(m_d -
m_u)/\bigl(m_s-(m_u+m_d)/2 \bigr)$. Experimental information on the branching
ratio for $D_s^* \rightarrow D_s \pi^0$ can provide insight into the pattern of
$SU(3)$ violation in radiative $D^*$ decays.Comment: 7 pages with 2 figures not included but available upon request,
CALT-68-191

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