38,402 research outputs found
The ballistic acceleration of a supercurrent in a superconductor
One of the most primitive but elusive current-voltage (I-V) responses of a
superconductor is when its supercurrent grows steadily after a voltage is first
applied. The present work employed a measurement system that could
simultaneously track and correlate I(t) and V(t) with sub-nanosecond timing
accuracy, resulting in the first clear time-domain measurement of this
transient phase where the quantum system displays a Newtonian like response.
The technique opens doors for the controlled investigation of other time
dependent transport phenomena in condensed-matter systems.Comment: 4 pages, 3 figure
Holography with Gravitational Chern-Simons Term
The holographic description in the presence of gravitational Chern-Simons
term is studied. The modified gravitational equations are integrated by using
the Fefferman-Graham expansion and the holographic stress-energy tensor is
identified. The stress-energy tensor has both conformal anomaly and
gravitational or, if re-formulated in terms of the zweibein, Lorentz anomaly.
We comment on the structure of anomalies in two dimensions and show that the
two-dimensional stress-energy tensor can be reproduced by integrating the
conformal and gravitational anomalies. We study the black hole entropy in
theories with a gravitational Chern-Simons term and find that the usual
Bekenstein-Hawking entropy is modified. For the BTZ black hole the modification
is determined by area of the inner horizon. We show that the total entropy of
the BTZ black hole is precisely reproduced in a boundary CFT calculation using
the Cardy formula.Comment: 19 pages, Latex; v3: minor corrections, some clarification
Comparison of superoxide dismutase, allopurinol, coenzyme Q10, and glutathione for the prevention of warm ischemic injury
Search for magnetic monopoles using proportional counters filled with helium gas
Slow magnetic monopoles in cosmic rays have been searched at sea level with the detector which consists of seven layers of proportional counters filled with a mixture of He + 20% CH4. The velocities and the energy losses of the incident particles are measured. The upper limit of flux for the monopoles in the velocity range of 1 x 0.001 Beta 4 x 0.001 is 2.78 x 10 to the minus 12th power square centimeters sr sec of 90% confidence level
Analytical treatment of SUSY Quasi-normal modes in a non-rotating Schwarzschild black hole
We use the Fock-Ivanenko formalism to obtain the Dirac equation which
describes the interaction of a massless 1/2-spin neutral fermion with a
gravitational field around a Schwarzschild black hole (BH). We obtain
approximated analytical solutions for the eigenvalues of the energy
(quasi-normal frequencies) and their corresponding eigenstates (quasi-normal
states). The interesting result is that all the excited states [and their
supersymmetric (SUSY) partners] have a purely imaginary frequency, which can be
expressed in terms of the Hawking temperature. Furthermore, as one expects for
SUSY Hamiltonians, the isolated bottom state has a real null energy eigenvalue.Comment: Version to be published in European Physical Journal
NOMAD: Non-locking, stOchastic Multi-machine algorithm for Asynchronous and Decentralized matrix completion
We develop an efficient parallel distributed algorithm for matrix completion,
named NOMAD (Non-locking, stOchastic Multi-machine algorithm for Asynchronous
and Decentralized matrix completion). NOMAD is a decentralized algorithm with
non-blocking communication between processors. One of the key features of NOMAD
is that the ownership of a variable is asynchronously transferred between
processors in a decentralized fashion. As a consequence it is a lock-free
parallel algorithm. In spite of being an asynchronous algorithm, the variable
updates of NOMAD are serializable, that is, there is an equivalent update
ordering in a serial implementation. NOMAD outperforms synchronous algorithms
which require explicit bulk synchronization after every iteration: our
extensive empirical evaluation shows that not only does our algorithm perform
well in distributed setting on commodity hardware, but also outperforms
state-of-the-art algorithms on a HPC cluster both in multi-core and distributed
memory settings
On the implications of a dilaton in gauge theory
Some recent work on the implications of a dilaton in 4d gauge theories are
revisited. In part I of this paper we see how an effective dilaton coupling to
gauge kinetic term provides a simple attractive mechanism to generate
confinement. In particular, we put emphasis on the derivation of confining
analytical solutions and look into the problem how dilaton degrees of freedom
modify Coulom potential and when a confining phase occurs. In part II, we solve
the semi-relativistic wave equation, for Dick interquark potential using the
Shifted l-expansion technique (SLET) in the heavy quarkonium sector. The
results of this phenomenological analysis proves that these effective theories
can be relevant to model quark confinement and may shed some light on
confinement mechanism.Comment: 8 pages. Talk given at CTP Symposium on Supersymmetry at LHC:
Theoretical and Experimental Prospectives, Cairo, Egypt, 11-14 Mar 200
Two-dimensional mapping of triaxial strain fields in a multiferroic BiFeO3 thin film using scanning x-ray microdiffraction
The dramatically enhanced polarizations and saturation magnetizations observed in the epitaxially constrained BiFeO3 (BFO) thin films with their pronounced grain-orientation dependence have attracted much attention and are attributed largely to the constrained in-plane strain. Thus, it is highly desirable to directly obtain information on the two-dimensional (2D) distribution of the in-plane strain and its correlation with the grain orientation of each corresponding microregion. Here the authors report a 2D quantitative mapping of the grain orientation and the local triaxial strain field in a 250 nm thick multiferroic BFO film using a synchrotron x-ray microdiffraction technique. This direct scanning measurement demonstrates that the deviatoric component of the in-plane strain tensor is between 5x10(-3) and 6x10(-3) and that the local triaxial strain is fairly well correlated with the grain orientation in that particular region. (c) 2007 American Institute of Physics.X1145Nsciescopu
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