1,169 research outputs found
Control of black hole evaporation?
Contradiction between Hawking's semi-classical arguments and string theory on
the evaporation of black hole has been one of the most intriguing problems in
fundamental physics. A final-state boundary condition inside the black hole was
proposed by Horowitz and Maldacena to resolve this contradiction. We point out
that original Hawking effect can be also regarded as a separate boundary
condition at the event horizon for this scenario. Here, we found that the
change of Hawking boundary condition may affect the information transfer from
the initial collapsing matter to the outgoing Hawking radiation during
evaporation process and as a result the evaporation process itself,
significantly.Comment: Journal of High Energy Physics, to be publishe
Universality of Regge and vibrational trajectories in a semiclassical model
The orbital and radial excitations of light-light mesons are studied in the
framework of the dominantly orbital state description. The equation of motion
is characterized by a relativistic kinematics supplemented by the usual funnel
potential with a mixed scalar and vector confinement. The influence of finite
quark masses and potential parameters on Regge and vibrational trajectories is
discussed. The case of heavy-light mesons is also presented.Comment: 12 page
Thermal Radiation from Nucleons and Mesons
Thermal photon emission rates due to meson-nucleon interactions have been
evaluated. An exhaustive set of reactions involving p(\bar p), n(\bar n), rho,
omega, a_1, pi and eta is seen to provide a sizeable contribution to the
emission rate from hot hadronic matter. Contributions from baryonic resonances
are found to be negligibly small
Generating a checking sequence with a minimum number of reset transitions
Given a finite state machine M, a checking sequence is an input sequence that is guaranteed to lead to a failure if the implementation under test is faulty and has no more states than M. There has been much interest in the automated generation of a short checking sequence from a finite state machine. However, such sequences can contain reset transitions whose use can adversely affect both the cost of applying the checking sequence and the effectiveness of the checking sequence. Thus, we sometimes want a checking sequence with a minimum number of reset transitions rather than a shortest checking sequence. This paper describes a new algorithm for generating a checking sequence, based on a distinguishing sequence, that minimises the number of reset transitions used.This work was supported in part by Leverhulme Trust grant number F/00275/D, Testing State Based Systems, Natural Sciences and Engineering Research Council (NSERC) of Canada grant number RGPIN 976, and Engineering and Physical Sciences Research Council grant number GR/R43150, Formal Methods and Testing (FORTEST)
Scheme and Scale Dependence of Charm Production in Neutrino Scattering
We discuss some theoretical uncertainties in the calculation of the cross
section for charm production in charged current deep inelastic neutrino
scattering related to ambiguities in the treatment of terms which are singular
in the limit of a vanishing charm mass. In particular we compare the so-called
variable flavour scheme where these terms are absorbed in the parton
distribution functions containing the charm as an active flavour, with the
so-called fixed flavour scheme with no charm mass subtraction where the charm
appears only in the final state of fixed-order scattering matrix elements.
Using available parametrizations of parton distribution functions we find that
the two schemes lead to largely differing results for separate structure
functions whereas the differences cancel to a large extent in the total cross
section in that kinematical region which has been measured so far.Comment: 20pages, uuencoded postscript, figures include
Constraints on the Charged Higgs Sector from the Tevatron Collider Data on Top Quark Decay
The top quark data in the lepton plus channel offers a viable probe
for the charged Higgs boson signal. We analyse the recent Tevatron collider
data in this channel to obtain a significant limit on the mass in the
large region.Comment: 8 pages, LaTeX file; 2 figures included (PS files
Extraction of the D13(1520) photon-decay couplings from pion- and eta-photoproduction data
We compare results for the D13(1520) photon-decay amplitudes determined in
analyses of eta- and pion-photoproduction data. The ratio of helicity
amplitudes (A_3/2 / A_1/2), determined from eta-photoproduction data, is quite
different from that determined in previous analyses of pion-photoproduction
data. We consider how strongly the existing pion-photoproduction data constrain
both this ratio and the individual photon-decay amplitudes.Comment: 7 pages, 2 figure
Radioactive waste microbiology: predicting microbial survival and activity in changing extreme environments
The potential for microbial activity to occur within the engineered barrier system (EBS) of a geological disposal facility (GDF) for radioactive waste is acknowledged by waste management organizations as it could affect many aspects of the safety functions of a GDF. Microorganisms within an EBS will be exposed to changing temperature, pH, radiation, salinity, saturation, and availability of nutrient and energy sources, which can limit microbial survival and activity. Some of the limiting conditions are incorporated into GDF designs for safety reasons, including the high pH of cementitious repositories, the limited pore space of bentonite-based repositories, or the high salinity of GDFs in evaporitic geologies. Other environmental conditions such as elevated radiation, temperature, and desiccation, arise as a result of the presence of high heat generating waste (HHGW). Here, we present a comprehensive review of how environmental conditions in the EBS may limit microbial activity, covering HHGW and lower heat generating waste (LHGW) in a range of geological environments. We present data from the literature on the currently recognized limits to life for each of the environmental conditions described above, and nutrient availability to establish the potential for life in these environments. Using examples where each variable has been modelled for a particular GDF, we outline the times and locations when that variable can be expected to limit microbial activity. Finally, we show how this information for multiple variables can be used to improve our understanding of the potential for microbial activity to occur within the EBS of a GDF and, more broadly, to understand microbial life in changing environments exposed to multiple extreme conditions
Scalar Glueball Decay Into Pions In Effective Theory
We discuss the mixing between the sigma meson sigma and the "pure" glueball
field H and study the decays of the scalar glueball candidates f_0(1370),
f_0(1500) and f_0(1710) (a linear combination of sigma and H) into two pions in
an effective linear sigma model.Comment: 10 pages and 3 figures (an extended version of hep-ph/9805412), to
appear in Phys. Rev.
Event-by-event fluctuations in collective quantities
We discuss an event-by-event fluctuation analysis of particle production in
heavy ion collisions. We compare different approaches to the evaluation of the
event-by-event dynamical fluctuations in quantities defined on groups of
particles, such quantities as mean transverse momentum, transverse momentum
spectra slope, strength of anisotropic flow, etc.. The direct computation of
the dynamical fluctuations and the sub-event method are discussed in more
detail. We also show how the fluctuation in different variables can be related
to each other.Comment: LaTex, 14 pages and 5 figures. 2 references adde
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