3,473 research outputs found
Determination of the internal structure of neutron stars from gravitational wave spectra
In this paper the internal structure of a neutron star is shown to be
inferrable from its gravitational-wave spectrum. Iteratively applying the
inverse scheme of the scaled coordinate logarithmic perturbation method for
neutron stars proposed by Tsui and Leung [Astrophys. J. {\bf 631}, 495 (2005)],
we are able to determine the mass, the radius and the mass distribution of a
star from its quasi-normal mode frequencies of stellar pulsation. In addition,
accurate equation of state of nuclear matter can be obtained from such
inversion scheme. Explicit formulas for the case of axial -mode oscillation
are derived here and numerical results for neutron stars characterized by
different equations of state are shown.Comment: 26 pages, 14 figures, submitted to Physical Review
Perturbative Analysis of Universality and Individuality in Gravitational Waves from Neutron Stars
The universality observed in gravitational wave spectra of non-rotating
neutron stars is analyzed here. We show that the universality in the axial
oscillation mode can be reproduced with a simple stellar model, namely the
centrifugal barrier approximation (CBA), which captures the essence of the
Tolman VII model of compact stars. Through the establishment of scaled
co-ordinate logarithmic perturbation theory (SCLPT), we are able to explain and
quantitatively predict such universal behavior. In addition, quasi-normal modes
of individual neutron stars characterized by different equations of state can
be obtained from those of CBA with SCLPT.Comment: 29 pages, 10 figures, submitted to Astrophysical Journa
Zener Tunneling Between Landau Orbits in a High-Mobility Two-Dimensional Electron Gas
Magnetotransport in a laterally confined two-dimensional electron gas (2DEG)
can exhibit modified scattering channels owing to a tilted Hall potential.
Transitions of electrons between Landau levels with shifted guiding centers can
be accomplished through a Zener tunneling mechanism, and make a significant
contribution to the magnetoresistance. A remarkable oscillation effect in weak
field magnetoresistance has been observed in high-mobility 2DEGs in
GaAs-AlGaAs heterostructures, and can be well explained by the
Zener mechanism.Comment: 5 pages, 4 figures. Text slightly shortened, figures resize
Magnetic Field Induced Insulating Phases at Large
Exploring a backgated low density two-dimensional hole sample in the large
regime we found a surprisingly rich phase diagram. At the highest
densities, beside the , 2/3, and 2/5 fractional quantum Hall states,
we observe both of the previously reported high field insulating and reentrant
insulating phases. As the density is lowered, the reentrant insulating phase
initially strengthens, then it unexpectedly starts weakening until it
completely dissapears. At the lowest densities the terminal quantum Hall state
moves from to . The intricate behavior of the insulating
phases can be explained by a non-monotonic melting line in the -
phase space
Josephson Plasma Resonance as a Structural Probe of Vortex Liquid
Recent developments of the Josephson plasma resonance and transport c-axis
measurements in layered high T superconductors allow to probe Josephson
coupling in a wide range of the vortex phase diagram. We derive a relation
between the field dependent Josephson coupling energy and the density
correlation function of the vortex liquid. This relation provides a unique
opportunity to extract the density correlation function of pancake vortices
from the dependence of the plasma resonance on the -component of the
magnetic field at a fixed -axis component.Comment: 4 pages, 1 fugure, accepted to Phys. Rev. Let
Quantization of the diagonal resistance: Density gradients and the empirical resistance rule in a 2D system
We have observed quantization of the diagonal resistance, R_xx, at the edges
of several quantum Hall states. Each quantized R_xx value is close to the
difference between the two adjacent Hall plateaus in the off-diagonal
resistance, R_xy. Peaks in R_xx occur at different positions in positive and
negative magnetic fields. Practically all R_xx features can be explained
quantitatively by a ~1%/cm electron density gradient. Therefore, R_xx is
determined by R_xy and unrelated to the diagonal resistivity rho_xx. Our
findings throw an unexpected light on the empirical resistivity rule for 2D
systems
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