7,608 research outputs found
Hawking radiation of a vector field and gravitational anomalies
Recently, the relation between Hawking radiation and gravitational anomalies
has been used to estimate the flux of Hawking radiation for a large class of
black objects. In this paper, we extend the formalism, originally proposed by
Robinson and Wilczek, to the Hawking radiation of vector particles (photons).
It is explicitly shown, with Hamiltonian formalism, that the theory of an
electromagnetic field on d-dimensional spherical black holes reduces to one of
an infinite number of massive complex scalar fields on 2-dimensional spacetime,
for which the usual anomaly-cancellation method is available. It is found that
the total energy emitted from the horizon for the electromagnetic field is just
(d-2) times as that for a scalar field. The results support the picture that
Hawking radiation can be regarded as an anomaly eliminator on horizons.
Possible extensions and applications of the analysis are discussed.Comment: 14 pages, 1 figur
Induced Magnetic Ordering by Proton Irradiation in Graphite
We provide evidence that proton irradiation of energy 2.25 MeV on
highly-oriented pyrolytic graphite samples triggers ferro- or ferrimagnetism.
Measurements performed with a superconducting quantum interferometer device
(SQUID) and magnetic force microscopy (MFM) reveal that the magnetic ordering
is stable at room temperature.Comment: 3 Figure
Proton-induced magnetic order in carbon: SQUID measurements
In this work we have studied systematically the changes in the magnetic
behavior of highly oriented pyrolytic graphite (HOPG) samples after proton
irradiation in the MeV energy range. Superconducting quantum interferometer
device (SQUID) results obtained from samples with thousands of localized spots
of micrometer size as well on samples irradiated with a broad beam confirm
previously reported results. Both, the para- and ferromagnetic contributions
depend strongly on the irradiation details. The results indicate that the
magnetic moment at saturation of spots of micrometer size is of the order of
emu.Comment: Invited contribution at ICACS2006 to be published in Nucl. Instr. and
Meth. B. 8 pages and 6 figure
Beyond the standard model physics at RHIC in polarized pp collision
A polarized hadron collider experiment must have a great discovery potential
for a search of physics beyond the standard model. Experimental data of various
symmetry tests at RHIC are going to be obtained within a few years. The author
developed a simulation tool, studying a sensitivity of hunting contact
interaction at RHIC by measuring parity violating spin asymmetries.Comment: 8 pages, 9 figure, Proc. of Praha-SPIN-200
Anomalous expansion and phonon damping due to the Co spin-state transition in RCoO_3 with R = La, Pr, Nd and Eu
We present a combined study of the thermal expansion and the thermal
conductivity of the perovskite series RCoO_3 with R = La, Nd, Pr and Eu. The
well-known spin-state transition in LaCoO_3 is strongly affected by the
exchange of the R ions due to their different ionic radii, i.e. chemical
pressure. This can be monitored in detail by measurements of the thermal
expansion, which is a highly sensitive probe for detecting spin-state
transitions. The Co ions in the higher spin state act as additional scattering
centers for phonons, therefore suppressing the phonon thermal conductivity.
Based on the analysis of the interplay between spin-state transition and heat
transport, we present a quantitative model of the thermal conductivity for the
entire series. In PrCoO_3, an additional scattering effect is active at low
temperatures. This effect arises from the crystal field splitting of the 4f
multiplet, which allows for resonant scattering of phonons between the various
4f levels.Comment: 15 pages including 5 figure
Anomalies, Hawking Radiations and Regularity in Rotating Black Holes
This is an extended version of our previous letter hep-th/0602146. In this
paper we consider rotating black holes and show that the flux of Hawking
radiation can be determined by anomaly cancellation conditions and regularity
requirement at the horizon. By using a dimensional reduction technique, each
partial wave of quantum fields in a d=4 rotating black hole background can be
interpreted as a (1+1)-dimensional charged field with a charge proportional to
the azimuthal angular momentum m. From this and the analysis gr-qc/0502074,
hep-th/0602146 on Hawking radiation from charged black holes, we show that the
total flux of Hawking radiation from rotating black holes can be universally
determined in terms of the values of anomalies at the horizon by demanding
gauge invariance and general coordinate covariance at the quantum level. We
also clarify our choice of boundary conditions and show that our results are
consistent with the effective action approach where regularity at the future
horizon and vanishing of ingoing modes at r=\infty are imposed (i.e. Unruh
vacuum).Comment: 21 pages, minor corrections, added an appendix to summarize our
notations for the Kaluza-Klein reductio
Integrated analysis of hydrogen embrittlement mechanisms of a steel from its mechanical behaviours and atom probe tomography
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