190,772 research outputs found
GPS source solution of the 2004 Parkfield earthquake
We compute a series of finite-source parameter inversions of the fault
rupture of the 2004 Parkfield earthquake based on 1 Hz GPS records only. We
confirm that some of the co-seismic slip at shallow depth (<5 km) constrained
by InSAR data processing results from early post-seismic deformation. We also
show 1) that if located very close to the rupture, a GPS receiver can saturate
while it remains possible to estimate the ground velocity (~1.2 m/s) near the
fault, 2) that GPS waveforms inversions constrain that the slip distribution at
depth even when GPS monuments are not located directly above the ruptured areas
and 3) the slip distribution at depth from our best models agree with that
recovered from strong motion data. The 95th percentile of the slip amplitudes
for rupture velocities ranging from 2 to 5 km/s is, 55 +/- 6 cm.Comment: 24 pages including supp. material
Surplus Angle and Sign-flipped Coulomb Force in Projectable Horava-Lifshitz Gravity
We obtain the static spherically symmetric vacuum solutions of
Horava-Lifshitz gravity theory, imposing the detailed balance condition only in
the UV limit. We find the solutions in two different coordinate systems, the
Painlev\'e-Gullstrand coordinates and the Poincare coordinates, to examine the
consequences of imposing the projectability condition. The solutions in two
coordinate systems are distinct due to the non-relativistic nature of the HL
gravity. In the Painleve-Gullstrand coordinates complying with the
projectability condition, the solution involves an additional integration
constant which yields surplus angle and implies attractive Coulomb force
between same charges.Comment: 13 page
Cosmic D- and DF-strings from D3Dbar3: Black Strings and BPS Limit
We study D- and DF-strings in a D3 system by using
Dirac-Born-Infeld type action. In the presence of an electric flux from the
transverse direction, we discuss gravitating thick D-string solutions of a
spatial manifold, , in which straight D-strings
stretched along the R direction are attached to the south and north
poles of the two-sphere. There is a horizon along its equator, which means the
structure of black strings is formed. We also discuss the BPS limit for thin
parallel D- and DF-strings in both flat and curved spacetime. We obtain the BPS
sum rule for an arbitrarily-separated multi-string configuration with a
Gaussian type tachyon potential. At the site of each thin BPS D(F)-string, the
pressure takes a finite value. We find that there exists a maximum deficit
angle in the conical geometry induced by thin BPS D- and DF-strings.Comment: 24 pages, 5 figure
Testing whether all eigenstates obey the Eigenstate Thermalization Hypothesis
We ask whether the Eigenstate Thermalization Hypothesis (ETH) is valid in a
strong sense: in the limit of an infinite system, {\it every} eigenstate is
thermal. We examine expectation values of few-body operators in highly-excited
many-body eigenstates and search for `outliers', the eigenstates that deviate
the most from ETH. We use exact diagonalization of two one-dimensional
nonintegrable models: a quantum Ising chain with transverse and longitudinal
fields, and hard-core bosons at half-filling with nearest- and
next-nearest-neighbor hopping and interaction. We show that even the most
extreme outliers appear to obey ETH as the system size increases, and thus
provide numerical evidences that support ETH in this strong sense. Finally,
periodically driving the Ising Hamiltonian, we show that the eigenstates of the
corresponding Floquet operator obey ETH even more closely. We attribute this
better thermalization to removing the constraint of conservation of the total
energy.Comment: 9 pages, 6 figures. Updated references and clarified some argument
Exact Rolling Tachyon in Noncommutative Field Theory
We study the exact rolling tachyon solutions in DBI type noncommutative field
theory with a constant open string metric and noncommutative parameter on an
unstable D-brane. Functional shapes of the obtained solutions span all
possible homogeneous rolling tachyon configurations; that is, they are
hyperbolic-cosine, hyperbolic-sine, and exponential under runaway NC
tachyon potential. Even if general DBI type NC electric field is turned on,
only a constant electric field satisfies the equations of motion, and again,
exact rolling tachyon solutions are obtained.Comment: 13 pages, minor correction
Off-diagonal magnetoimpedance in field-annealed Co-based amorphous ribbons
The off-diagonal magnetoimpedance in field-annealed CoFeSiB amorphous ribbons
was measured in the low-frequency range using a pick-up coil wound around the
sample. The asymmetric two-peak behavior of the field dependence of the
off-diagonal impedance was observed. The asymmetry is attributed to the
formation of a hard magnetic crystalline phase at the ribbon surface. The
experimental results are interpreted in terms of the surface impedance tensor.
It is assumed that the ribbon consists of an inner amorphous region and surface
crystalline layers. The coupling between the crystalline and amorphous phases
is described through an effective bias field. A qualitative agreement between
the calculated dependences and experimental data is demonstrated. The results
obtained may be useful for development of weak magnetic-field sensors.Comment: 19 pages, 6 figure
Scalar Hair of Global Defect and Black Brane World
We consider a complex scalar field in (p+3)-dimensional bulk with a negative
cosmological constant and study global vortices in two extra-dimensions. We
reexamine carefully the coupled scalar and Einstein equations, and show that
the boundary value of scalar amplitude at infinity of the extra-dimensions
should be smaller than vacuum expectation value. The brane world has a
cigar-like geometry with an exponentially decaying warp factor and a flat thick
p-brane is embedded. Since a coordinate transformation identifies the obtained
brane world as a black p-brane world bounded by a horizon, this strange
boundary condition of the scalar amplitude is understood as existence of a
short scalar hair.Comment: 26 pages, 2 figure
Quantum paramagnetic ground states on the honeycomb lattice and field-induced transition to N\'eel order
Motivated by recent experiments on BiMnO(NO), and a
broader interest arising from numerical work on the honeycomb lattice Hubbard
model, we have studied the effect of a magnetic field on honeycomb lattice spin
models with quantum paramagnetic ground states. For a model with frustrating
second-neighbor exchange, , we use a Lindemann-like criterion within spin
wave theory to show that N\'eel order melts beyond a critical . The
critical increases with a magnetic field, implying the existence of a
field-induced paramagnet-N\'eel transition over a range of . We also study
bilayer model using a spin- generalization of bond operator mean field
theory. We show that there is a N\'eel-dimer transition for various spin values
with increasing bilayer coupling, and that the resulting interlayer dimer state
undergoes a field induced transition into a state with transverse N\'eel order.
Finally, we study a spin-3/2 model which interpolates between the Heisenberg
model and the Affleck-Kennedy-Lieb-Tasaki (AKLT) parent Hamiltonian. Using
exact diagonalization, we compute the fidelity susceptibility to locate the
Neel-AKLT quantum critical point, obtain the spin gap of the AKLT parent
Hamiltonian, and argue that AKLT state also undergoes field-induced Neel
ordering.Comment: 8 pages, revised longer version of arXiv:1012.0316. Corrected factor
of 2 error in Eq.[16], replotted Fig.[4] and revised the critical
needed to stabilize interlayer dimer state. We thank S. V. Isakov for
discussions which uncovered this erro
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