30 research outputs found
Surface gravity and Hawking temperature from entropic force viewpoint
We consider a freely falling holographic screen for the Schwarzschild and
Reissner-Nordstr\"om black holes and evaluate the entropic force \`a la
Verlinde. When the screen crosses the event horizon, the temperature of the
screen agrees to the Hawking temperature and the entropic force gives rise to
the surface gravity for both of the black holes.Comment: 7 pages, 1 figure; RevTeX
Brans-Dicke Gravity from Entropic Viewpoint
We interpret the Brans-Dicke gravity from entropic viewpoint. We first apply
the Verlinde's entropic formalism in the Einstein frame, then perform the
conformal transformation which connects the Einstein frame to the Jordan frame.
The transformed result yields the equation of motion of the Brans-Dicke theory
in the Jordan frame.Comment: Title changed, minor changes to match the published versio
A Millimeter-scale Single Charged Particle Dosimeter for Cancer Radiotherapy
This paper presents a millimeter-scale CMOS 6464 single charged
particle radiation detector system for external beam cancer radiotherapy. A
11 diode measures energy deposition by a single charged
particle in the depletion region, and the array design provides a large
detection area of 512512 . Instead of sensing the voltage drop
caused by radiation, the proposed system measures the pulse width, i.e., the
time it takes for the voltage to return to its baseline. This obviates the need
for using power-hungry and large analog-to-digital converters. A prototype ASIC
is fabricated in TSMC 65 nm LP CMOS process and consumes the average static
power of 0.535 mW under 1.2 V analog and digital power supply. The
functionality of the whole system is successfully verified in a clinical 67.5
MeV proton beam setting. To our' knowledge, this is the first work to
demonstrate single charged particle detection for implantable in-vivo
dosimetry
Anyonic Bogomol'nyi Solitons in a Gauged O(3) Sigma Model
We introduce the self-dual abelian gauged sigma models where the
Maxwell and Chern-Simons terms constitute the kinetic terms for the gauge
field. These models have quite rich structures and various limits. Our models
are found to exhibit both symmetric and broken phases of the gauge group. We
discuss the pure Chern-Simons limit in some detail and study rotationally
symmetric solitons.Comment: 14 pages, 6 Postscript figures uuencoded, written in REVTe
Noncommutative Solitonic Black Hole
We investigate solitonic black hole solutions in three dimensional
noncommutative spacetime. We do this in gravity with negative cosmological
constant coupled to a scalar field. Noncommutativity is realized with the Moyal
product which is expanded up to first order in the noncommutativity parameter
in two spatial directions. With numerical simulation we study the effect of
noncommutativity by increasing the value of the noncommutativity parameter
starting from commutative solutions. We find that even a regular soliton
solution in the commutative case becomes a black hole solution when the
noncommutativity parameter reaches a certain value.Comment: 11 pages, 5 figures, LaTeX format, appendix added, minor correction
Global Vortex and Black Cosmic String
We study global vortices coupled to (2+1) dimensional gravity with negative
cosmological constant. We found nonsingular vortex solutions in -theory
with a broken U(1) symmetry, of which the spacetimes do not involve physical
curvature singularity. When the magnitude of negative cosmological constant is
larger than a critical value at a given symmetry breaking scale, the spacetime
structure is a regular hyperbola, however it becomes a charged black hole when
the magnitude of cosmological constant is less than the critical value. We
explain through duality transformation the reason why static global vortex
which is electrically neutral forms black hole with electric charge. Under the
present experimental bound of the cosmological constant, implications on
cosmology as a straight black cosmic string is also discussed in comparison
with global U(1) cosmic string in the spacetime of the zero cosmological
constant.Comment: 35 pages, Late