864 research outputs found
Strong-coupling Jet Energy Loss from AdS/CFT
We propose a novel definition of a holographic light hadron jet and consider
the phenomenological consequences, including the very first fully
self-consistent, completely strong-coupling calculation of the jet nuclear
modification factor , which we find compares surprisingly well with
recent preliminary data from LHC. We show that the thermalization distance for
light parton jets is an extremely sensitive function of the \emph{a priori}
unspecified string initial conditions and that worldsheets corresponding to
non-asymptotic energy jets are not well approximated by a collection of null
geodesics. Our new string jet prescription, which is defined by a separation of
scales from plasma to jet, leads to the re-emergence of the late-time Bragg
peak in the instantaneous jet energy loss rate; unlike heavy quarks, the energy
loss rate is unusually sensitive to the very definition of the string theory
object itself. A straightforward application of the new jet definition leads to
significant jet quenching, even in the absence of plasma. By renormalizing the
in-medium suppression by that in the vacuum we find qualitative agreement with
preliminary CMS data in our simple plasma brick model. We
close with comments on our results and an outlook on future work.Comment: 28 pages, 9 figure
Managing soil biodiversity: The New Zealand experience
Species diversity is a very important component of a healthy soil ecosystem, and a necessary condition for long-term sustainable development. However, it is widely recognised that soil degradation and species extinction are on the increase in New Zealand, as land resources come under pressure from urban expansion and modern agribusiness. New Zealand's soils, flora and fauna have evolved many unique elements during their long isolation from other land masses. Habitat destruction and introduced plants and animals have, therefore, had increasingly detrimental effects on indigenous biodiversity. New Zealand must conserve what remains
Application of AdS/CFT in Nuclear Physics
We review some recent progress in studying the nuclear physics especially nucleon-nucleon (NN) force within the gauge-gravity duality, in context of noncritical string theory. Our main focus is on the holographic QCD model based on the AdS6 background. We explain the noncritical holography model and obtain the vector-meson spectrum and pion decay constant. Also, we study the NN interaction in this frame and calculate the nucleonmeson coupling constants. A further topic covered is a toy model for calculating the light nuclei potential. In particular, we calculate the light nuclei binding energies and also excited energies of some available excited states. We compare our results with the results of other nuclear models and also with the experimental data. Moreover, we describe some other issues which are studied using the gauge-gravity duality
Entropy of gravitationally collapsing matter in FRW universe models
We look at a gas of dust and investigate how its entropy evolves with time
under a spherically symmetric gravitational collapse. We treat the problem
perturbatively and find that the classical thermodynamic entropy does actually
increase to first order when one allows for gravitational potential energy to
be transferred to thermal energy during the collapse. Thus, in this situation
there is no need to resort to the introduction of an intrinsic gravitational
entropy in order to satisfy the second law of thermodynamics.Comment: 9 pages, 4 figures. Major changes from previous version. We consider
only thermodynamic entropy in this version. Published in PR
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