426 research outputs found
Do static sources respond to massive scalar particles from the Hawking radiation as uniformly accelerated ones do in the inertial vacuum?
We revisit the recently found equivalence for the response of a static scalar
source interacting with a {\em massless} Klein-Gordon field when the source is
(i) static in Schwarzschild spacetime, in the Unruh vacuum associated with the
Hawking radiation and (ii) uniformly accelerated in Minkowski spacetime, in the
inertial vacuum, provided that the source's proper acceleration is the same in
both cases. It is shown that this equivalence is broken when the massless
Klein-Gordon field is replaced by a {\em massive} one.Comment: 4 pages, 2 figure
A 'cyanoacrylate case' for developing fingerprints in cars
A portable case has been developed by which cyanoacrylate (super glue) fuming can be used inside a vehicle suspected of being involved in serious crime. The car itself serves as a fumigation chamber and the cyanoacrylate vapours are fed into the car via a hose. Connected to the hose and suspended inside the car is a vapour diffuser. The cyanoacrylate originates from a portable case where there is a sealed heater and also a command panel with hygrometer and thermometer for a technician to control the process. There is also space inside the case for other necessary equipment
Interaction of Hawking radiation with static sources in deSitter and Schwarzschild-deSitter spacetimes
We study and look for similarities between the response rates and of a static scalar source
with constant proper acceleration interacting with a massless,
conformally coupled Klein-Gordon field in (i) deSitter spacetime, in the
Euclidean vacuum, which describes a thermal flux of radiation emanating from
the deSitter cosmological horizon, and in (ii) Schwarzschild-deSitter
spacetime, in the Gibbons-Hawking vacuum, which describes thermal fluxes of
radiation emanating from both the hole and the cosmological horizons,
respectively, where is the cosmological constant and is the black
hole mass. After performing the field quantization in each of the above
spacetimes, we obtain the response rates at the tree level in terms of an
infinite sum of zero-energy field modes possessing all possible angular
momentum quantum numbers. In the case of deSitter spacetime, this formula is
worked out and a closed, analytical form is obtained. In the case of
Schwarzschild-deSitter spacetime such a closed formula could not be obtained,
and a numerical analysis is performed. We conclude, in particular, that and do not coincide in
general, but tend to each other when or . Our
results are also contrasted and shown to agree (in the proper limits) with
related ones in the literature.Comment: ReVTeX4 file, 9 pages, 5 figure
Low-energy sector quantization of a massless scalar field outside a Reissner-Nordstrom black hole and static sources
We quantize the low-energy sector of a massless scalar field in the
Reissner-Nordstrom spacetime. This allows the analysis of processes involving
soft scalar particles occurring outside charged black holes. In particular, we
compute the response of a static scalar source interacting with Hawking
radiation using the Unruh (and the Hartle-Hawking) vacuum. This response is
compared with the one obtained when the source is uniformly accelerated in the
usual vacuum of the Minkowski spacetime with the same proper acceleration. We
show that both responses are in general different in opposition to the result
obtained when the Reissner-Nordstrom black hole is replaced by a Schwarzschild
one. The conceptual relevance of this result is commented.Comment: 12 pages (REVTEX), no figure
Latent solitons, black strings, black branes, and equations of state in Kaluza-Klein models
In Kaluza-Klein models with an arbitrary number of toroidal internal spaces,
we investigate soliton solutions which describe the gravitational field of a
massive compact object. We single out the physically interesting solution
corresponding to a point-like mass. For the general solution we obtain
equations of state in the external and internal spaces. These equations
demonstrate that the point-like mass soliton has dust-like equations of state
in all spaces. We also obtain the PPN parameters, which give the possibility to
obtain the formulas for perihelion shift, deflection of light and time delay of
radar echoes. Additionally, the gravitational experiments lead to a strong
restriction on the parameter of the model: . The point-like mass solution contradicts this restriction. The
condition satisfies the experimental limitation and defines a new
class of solutions which are indistinguishable from general relativity. We call
such solutions latent solitons. Black strings and black branes belong to this
class. Moreover, the condition of stability of the internal spaces singles out
black strings/branes from the latent solitons and leads uniquely to the black
string/brane equations of state , in the internal spaces and
to the number of the external dimensions . The investigation of
multidimensional static spherically symmetric perfect fluid with dust-like
equation of state in the external space confirms the above results.Comment: 8 pages, Revtex4, no figures, minor changes adde
Asymmetric wormholes in Palatini gravity: Energy conditions, absorption and quasibound states
We investigate the absorption properties of reflection-asymmetric wormholes
constructed via the thin-shell formalism in Palatini gravity.
Such wormholes come from the matching of two Reissner-Nordstr\"om spacetimes at
a time-like hypersurface (shell), which, according to the junction conditions
in Palatini gravity, can have positive or negative energy
density. Using numerical methods we investigate several configurations that
satisfy the junction conditions, and analyze how the parameters of the system
affect the absorption spectra. We confirm that the absorption cross section of
wormholes at low frequencies significantly departs from that of black holes,
and observe that in configurations made out of two naked singularities, the
absorption spectra exhibit new features due to the effective light ring
associated to the wormhole throat. The possibility of observing the presence of
resonances at high frequencies is also discussed.Comment: 18 pages, 13 figures, revtex4-2 styl
Multinational cooperation and intervention: small steps to better results
Through the latter years of the twentieth century and early years of the twenty-first century, there have been a number of high-profile multinational intervenÂtions by the international community in countries deemed to be sufficiently unÂstable to present a threat to global peace or, more controversially, to local popÂulations. Beginning with the tardy but largely successful intervention in the YuÂgoslav civil war in 1990 and culminating in the soon to conclude intervention in Afghanistan after the Al Qaeda attacks on the USA in 2001, there have also been military interventions in Iraq in 2003 and Libya in 2011. The list is not exhaustive. There have been other interventions elsewhere, but these particular examples of military intervention mainly conducted by western powers provide illuminatÂing insights into the success and, sometimes, the failure of such multinational security responses to perceived international threats
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