4,077 research outputs found
Minimal Length Effects on Tunnelling from Spherically Symmetric Black Holes
In this paper, we investigate effects of the minimal length on quantum
tunnelling from spherically symmetric black holes using the Hamilton-Jacobi
method incorporating the minimal length. We first derive the deformed
Hamilton-Jacobi equations for scalars and fermions, both of which have the same
expressions. The minimal length correction to the Hawking temperature is found
to depend on the black hole's mass and the mass and angular momentum of emitted
particles. Finally, we calculate a Schwarzschild black hole's luminosity and
find the black hole evaporates to zero mass in infinite time.Comment: 18 page
Holographic DC Conductivity for a Power-law Maxwell Field
We consider a neutral and static black brane background with a probe
power-law Maxwell field. Via the membrane paradigm, an expression for the
holographic DC conductivity of the dual conserved current is obtained. We also
discuss the dependence of the DC conductivity on the temperature, charge
density and spatial components of the external field strength in the boundary
theory. Our results show that there might be more than one phase in the
boundary theory. Phase transitions could occur where the DC conductivity or its
derivatives are not continuous. Specifically, we find that one phase possesses
a charge-conjugation symmetric contribution, negative magneto-resistance and
Mott-like behavior.Comment: 19 pages, 11 figures. arXiv admin note: text overlap with
arXiv:1711.0329
Iterative Row Sampling
There has been significant interest and progress recently in algorithms that
solve regression problems involving tall and thin matrices in input sparsity
time. These algorithms find shorter equivalent of a n*d matrix where n >> d,
which allows one to solve a poly(d) sized problem instead. In practice, the
best performances are often obtained by invoking these routines in an iterative
fashion. We show these iterative methods can be adapted to give theoretical
guarantees comparable and better than the current state of the art.
Our approaches are based on computing the importances of the rows, known as
leverage scores, in an iterative manner. We show that alternating between
computing a short matrix estimate and finding more accurate approximate
leverage scores leads to a series of geometrically smaller instances. This
gives an algorithm that runs in
time for any , where the term is comparable
to the cost of solving a regression problem on the small approximation. Our
results are built upon the close connection between randomized matrix
algorithms, iterative methods, and graph sparsification.Comment: 26 pages, 2 figure
Synthesizing and characterization of hole doped nickel based layer superconductor (LaSr)ONiAs
We report the synthesizing and characterization of the hole doped Ni-based
superconductor (. By substituting La with Sr, the
superconducting transition temperature is increased from 2.75 K of the
parent phase to 3.7 K at the doping levels x= 0.1 - 0.2. The curve
versus hole concentration shows a symmetric behavior as the electron
doped samples . The normal state resistivity in Ni-based
samples shows a good metallic behavior and reveals the absence of an anomaly
which appears in the Fe-based system at about 150 K, suggesting that this
anomaly is not a common feature for all systems. Hall effect measurements
indicate that the electron conduction in the parent phase is
dominated by electron-like charge carriers, while with more Sr doping, a
hole-like band will emerge and finally prevail over the conduction, and
accordingly the superconducting transition temperature increases.Comment: 4 pages, 5 figure
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