11,989 research outputs found
Photoacoustic wave propagating from normal into superconductive phases in Pb single crystals
Photoacoustic (PA) wave has been examined in a superconductor of the first
kind, Pb single crystal. The PA wave is induced by optical excitation of
electronic state and propagates from normal into superconductive phases below
T. It is clearly shown by wavelet analysis that the measured PA wave
includes two different components. The high-frequency component is
MHz-ultrasonic and the relative low-frequency one is induced by thermal wave.
The latter is observed in a similar manner irrespective of T. On the
other hand, the MHz-frequency component is obviously enhanced below T. The behavior is reproduced by the change of attenuation of longitudinal
ultrasonic wave and is consistent with BCS theory.Comment: 5 pages, 5 figures (fig.3 is colored), RevTeX4; the text is modifie
Supergravity in Dimensions
Supergravity theory in dimensions is studied. It is invariant
under supertransformations in 2 and 3 dimensions. One-loop divergence is
explicitly computed in the background field method and a nontrivial fixed point
is found. In quantizing the supergravity, a gauge fixing condition is devised
which explicitly isolates conformal and superconformal modes. The
renormalization of the gravitationally dressed operators is studied and their
anomalous dimensions are computed. Problems to use the dimensional reduction
are also examined.Comment: 36 pages, TIT/HEP-238, Imperial/TP/93-94/
-analog of the XXZ chain with a boundary
We study analog of the XXZ spin chain with a boundary
magnetic field h. We construct explicit bosonic formulas of the vacuum vector
and the dual vacuum vector with a boundary magnetic field. We derive integral
formulas of the correlation functions.Comment: 24 pages, LaTEX2
Resonant growth of stellar oscillations by incident gravitational waves
Stellar oscillation under the combined influences of incident gravitational
wave and radiation loss is studied in a simple toy model. The star is
approximated as a uniform density ellipsoid in the Newtonian gravity including
radiation damping through quadrupole formula. The time evolution of the
oscillation is significantly controlled by the incident wave amplitude ,
frequency and damping time . If a combination
exceeds a threshold value, which depends on the resonance mode, the resonant
growth is realized.Comment: 11 pages, 6 figures, Accepted for the publication in Classical and
Quantum Gravit
Effect of disorder outside the CuO planes on of copper oxide superconductors
The effect of disorder on the superconducting transition temperature
of cuprate superconductors is examined. Disorder is introduced into the cation
sites in the plane adjacent to the CuO planes of two single-layer
systems, BiSrLnCuO and
LaNdSrCuO. Disorder is controlled by changing
rare earth (Ln) ions with different ionic radius in the former, and by varying
the Nd content in the latter with the doped carrier density kept constant. We
show that this type of disorder works as weak scatterers in contrast to the
in-plane disorder produced by Zn, but remarkably reduces suggesting
novel effects of disorder on high- superconductivity.Comment: 5 pages, 5 figures, to be published in Phys. Rev. Let
R-mode Instability of Slowly Rotating Non-isentropic Relativistic Stars
We investigate properties of -mode instability in slowly rotating
relativistic polytropes. Inside the star slow rotation and low frequency
formalism that was mainly developed by Kojima is employed to study axial
oscillations restored by Coriolis force. At the stellar surface, in order to
take account of gravitational radiation reaction effect, we use a near-zone
boundary condition instead of the usually imposed boundary condition for
asymptotically flat spacetime. Due to the boundary condition, complex
frequencies whose imaginary part represents secular instability are obtained
for discrete -mode oscillations in some polytropic models. It is found that
such discrete -mode solutions can be obtained only for some restricted
polytropic models. Basic properties of the solutions are similar to those
obtained by imposing the boundary condition for asymptotically flat spacetime.
Our results suggest that existence of a continuous part of spectrum cannot be
avoided even when its frequency becomes complex due to the emission of
gravitational radiation.Comment: 10 pages, 4 figures, accepted for publlication in PR
The R-Mode Oscillations in Relativistic Rotating Stars
The axial mode oscillations are examined for relativistic rotating stars with
uniform angular velocity. Using the slow rotation formalism and the Cowling
approximation, we have derived the equations governing the r-mode oscillations
up to the second order with respect to the rotation. In the lowest order, the
allowed range of the frequencies is determined, but corresponding spatial
function is arbitrary. The spatial function can be decomposed in non-barotropic
region by a set of functions associated with the differential equation of the
second-order corrections. The equation however becomes singular in barotropic
region, and a single function can be selected to describe the spatial
perturbation of the lowest order. The frame dragging effect among the
relativistic effects may be significant, as it results in rather broad spectrum
of the r-mode frequency unlike in the Newtonian first-order calculation.Comment: 19 pages, 4 figures, AAS LaTeX, Accepted for publication in The
Astrophysical Journa
Possible direct method to determine the radius of a star from the spectrum of gravitational wave signals
We computed the spectrum of gravitational waves from a dust disk star of
radius R inspiraling into a Kerr black hole of mass M and specific angular
momentum a. We found that when R is much larger than the wave length of the
quasinormal mode, the spectrum has several peaks and the separation of peaks
is proportional to irrespective of M and a. This
suggests that the radius of the star in coalescing binary black hole - star
systems may be determined directly from the observed spectrum of gravitational
wave. This also suggests that the spectrum of the radiation may give us
important information in gravitational wave astronomy as in optical astronomy.Comment: 4 pages with 3 eps figures, revtex.sty, accepted for publication in
Phys. Rev. Let
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