1,514 research outputs found
Analytic Evaluation of the Decay Rate for Accelerated Proton
We evaluate the decay rate of the uniformly accelerated proton. We obtain an
analytic expression for inverse beta decay process caused by the acceleration.
We evaluate the decay rate both from the inertial frame and from the
accelerated frame where we should consider thermal radiation by Unruh effect.
We explicitly check that the decay rates obtained in both frame coincide with
each other.Comment: 11 page
Diamonds's Temperature: Unruh effect for bounded trajectories and thermal time hypothesis
We study the Unruh effect for an observer with a finite lifetime, using the
thermal time hypothesis. The thermal time hypothesis maintains that: (i) time
is the physical quantity determined by the flow defined by a state over an
observable algebra, and (ii) when this flow is proportional to a geometric flow
in spacetime, temperature is the ratio between flow parameter and proper time.
An eternal accelerated Unruh observer has access to the local algebra
associated to a Rindler wedge. The flow defined by the Minkowski vacuum of a
field theory over this algebra is proportional to a flow in spacetime and the
associated temperature is the Unruh temperature. An observer with a finite
lifetime has access to the local observable algebra associated to a finite
spacetime region called a "diamond". The flow defined by the Minkowski vacuum
of a (four dimensional, conformally invariant) quantum field theory over this
algebra is also proportional to a flow in spacetime. The associated temperature
generalizes the Unruh temperature to finite lifetime observers.
Furthermore, this temperature does not vanish even in the limit in which the
acceleration is zero. The temperature associated to an inertial observer with
lifetime T, which we denote as "diamond's temperature", is 2hbar/(pi k_b
T).This temperature is related to the fact that a finite lifetime observer does
not have access to all the degrees of freedom of the quantum field theory.Comment: One reference correcte
Deriving Bisimulation Congruences: 2-categories vs precategories
G-relative pushouts (GRPOs) have recently been proposed by the authors as a new foundation for Leifer and Milnerâs approach to deriving labelled bisimulation congruences from reduction systems. This paper develops the theory of GRPOs further, arguing that they provide a simple and powerful basis towards a comprehensive solution. As an example, we construct GRPOs in a category of âbunches and wirings.â We then examine the approach based on Milnerâs precategories and Leiferâs functorial reactive systems, and show that it can be recast in a much simpler way into the 2-categorical theory of GRPOs
The mechanism of the amidases: mutating the glutamate adjacent to the catalytic triad inactivates the enzyme due to substrate mispositioning
All known nitrilase superfamily amidase and carbamoylase structures have an additional glutamate thatis hydrogen bonded to the catalytic lysine in addition to the Glu, Lys, Cys âcatalytic triad.â In the amidase from Geobacillus pallidus, mutating this glutamate (Glu-142) to a leucine or aspartate renders the enzyme inactive. X-ray crystal structure determination shows that the structural integrity of the enzymeismaintained despite themutation with the catalytic cysteine (Cys-166), lysine (Lys-134), and glutamate (Glu- 59)in positions similar to those of the wild-type enzyme. In the case of the E142L mutant, a chloride ion is located in the position occupied by Glu-142 O 1 in the wild-type enzyme andinteracts with the active site lysine. In the case of the E142D mutant, this site is occupied by Asp-142 O1.In neither case is an atom located at the position of Glu-142 O 2 in the wild-type enzyme. The active site cysteine of the E142Lmutant was found to form aMichael adduct with acrylamide, which is a substrate of the wild-type enzyme, due to an interaction that places the double bond of the acrylamide rather than the amide carbonyl carbon adjacent to the active site cysteine. Our results demonstrate that in the wild-type active site a crucial role is played by the hydrogen bond between Glu-142 O 2 and the substrate amino groupin positioning the substrate with the correct stereoelectronic alignment to enable the nucleophilic attack on the carbonyl carbon by the catalytic cysteine
Decay of accelerated protons and the existence of the Fulling-Davies-Unruh effect
We investigate the weak decay of uniformly {\em accelerated protons} in the
context of {\em standard} Quantum Field Theory. Because the mean {\em proper}
lifetime of a particle is a scalar, the same value for this observable must be
obtained in the inertial and coaccelerated frames. We are only able to achieve
this equality by considering the Fulling-Davies-Unruh effect. This reflects the
fact that the Fulling-Davies-Unruh effect is mandatory for the consistency of
Quantum Field Theory. There is no question about its existence provided one
accepts the validity of standard Quantum Field Theory in flat spacetime.Comment: 4 pages (revtex), 1 figure, to appear in Phys. Rev. Let
Fluctuation-dissipation theorem and the Unruh effect of scalar and Dirac fields
We present a simple and systematic method to calculate the Rindler noise,
which is relevant to the analysis of the Unruh effect, by using the
fluctuation-dissipative theorem. To do this, we calculate the dissipative
coefficient explicitly from the equations of motion of the detector and the
field. This method gives not only the correct answer but also a hint as to the
origin of the apparent statistics inversion effect. Moreover, this method is
generalized to the Dirac field, by using the fermionic fluctuation-dissipation
theorem. We can thus confirm that the fermionic fluctuation-dissipation theorem
is working properly.Comment: 26 page
Remarks on geometric entropy
The recently discussed notion of geometric entropy is shown to be related to
earlier calculations of thermal effects in Rindler space. The evaluation is
extended to de Sitter space and to a two-dimensional black hole.Comment: 7p.,uses jyTeX,MUTP/94/
Inverse Temperature 4-vector in Special Relativity
There exist several prescriptions for identifying the notion of temperature
in special relativity. We argue that the inverse temperature 4-vector is the only viable option from the laws of thermodynamics, and is a future-directed timelike 4-vector. Using a superfluidity thought
experiment, one can show that is not necessarily along the time
direction of the comoving frame of the system, as is usually thought. It is
conjectured that, for an isolated system, the 4-vector is determined from the
entropy-maximum principle.Comment: 11 pages, revised versio
A Bisognano-Wichmann-like Theorem in a Certain Case of a Non Bifurcate Event Horizon related to an Extreme Reissner-Nordstr\"om Black Hole
Thermal Wightman functions of a massless scalar field are studied within the
framework of a ``near horizon'' static background model of an extremal R-N
black hole. This model is built up by using global Carter-like coordinates over
an infinite set of Bertotti-Robinson submanifolds glued together. The
analytical extendibility beyond the horizon is imposed as constraints on
(thermal) Wightman's functions defined on a Bertotti-Robinson sub manifold. It
turns out that only the Bertotti-Robinson vacuum state, i.e. , satisfies
the above requirement. Furthermore the extension of this state onto the whole
manifold is proved to coincide exactly with the vacuum state in the global
Carter-like coordinates. Hence a theorem similar to Bisognano-Wichmann theorem
for the Minkowski space-time in terms of Wightman functions holds with
vanishing ``Unruh-Rindler temperature''. Furtermore, the Carter-like vacuum
restricted to a Bertotti-Robinson region, resulting a pure state there, has
vanishing entropy despite of the presence of event horizons. Some comments on
the real extreme R-N black hole are given
Structural insight into African horsesickness virus infection
African horsesickness (AHS) is a devastating disease of horses. The disease is caused by the double-stranded RNA-containing African horsesickness virus (AHSV). Using electron cryomicroscopy and three-dimensional image reconstruction, we determined the architecture of an AHSV serotype 4 (AHSV-4) reference strain. The structure revealed triple-layered AHS virions enclosing the segmented genome and transcriptase complex. The innermost protein layer contains 120 copies of VP3, with the viral polymerase, capping enzyme, and helicase attached to the inner surface of the VP3 layer on the 5-fold axis, surrounded by double-stranded RNA. VP7 trimers form a second, T 13 layer on top of VP3. Comparative analyses of the structures of bluetongue virus and AHSV-4 confirmed that VP5 trimers form globular domains and VP2 trimers form triskelions, on the virion surface. We also identified an AHSV-7 strain with a truncated VP2 protein (AHSV-7 tVP2) which outgrows AHSV-4 in culture. Comparison of AHSV-7 tVP2 to bluetongue virus and AHSV-4 allowed mapping of two domains in AHSV-4 VP2, and one in bluetongue virus VP2, that are important in infection. We also revealed a protein plugging the 5-fold vertices in AHSV-4. These results shed light on virus-host interactions in an economically important orbivirus to help the informed design of new vaccines
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