1,451 research outputs found
Emergence of the fuzzy horizon through gravitational collapse
For a large enough Schwarzschild black hole, the horizon is a region of space
where gravitational forces are weak; yet it is also a region leading to
numerous puzzles connected to stringy physics. In this work, we analyze the
process of gravitational collapse and black hole formation in the context of
light-cone M theory. We find that, as a shell of matter contracts and is about
to reveal a black hole horizon, it undergoes a thermodynamic phase transition.
This involves the binding of D0 branes into D2's, and the new phase leads to
large membranes of the size of the horizon. These in turn can sustain their
large size through back-reaction and the dielectric Myers effect - realizing
the fuzzball proposal of Mathur and the Matrix black hole of M(atrix) theory.
The physics responsible for this phenomenon lies in strongly coupled 2+1
dimensional non-commutative dynamics. The phenomenon has a universal character
and appears generic.Comment: 24 pages, 4 figures; v2: minor clarifications, citations adde
Are Horned Particles the Climax of Hawking Evaporation?
We investigate the proposal by Callan, Giddings, Harvey and Strominger (CGHS)
that two dimensional quantum fluctuations can eliminate the singularities and
horizons formed by matter collapsing on the nonsingular extremal black hole of
dilaton gravity. We argue that this scenario could in principle resolve all of
the paradoxes connected with Hawking evaporation of black holes. However, we
show that the generic solution of the model of CGHS is singular. We propose
modifications of their model which may allow the scenario to be realized in a
consistent manner.Comment: 26 page
Copulas in finance and insurance
Copulas provide a potential useful modeling tool to represent the dependence structure
among variables and to generate joint distributions by combining given marginal
distributions. Simulations play a relevant role in finance and insurance. They are used to
replicate efficient frontiers or extremal values, to price options, to estimate joint risks, and so
on. Using copulas, it is easy to construct and simulate from multivariate distributions based
on almost any choice of marginals and any type of dependence structure. In this paper we
outline recent contributions of statistical modeling using copulas in finance and insurance.
We review issues related to the notion of copulas, copula families, copula-based dynamic and
static dependence structure, copulas and latent factor models and simulation of copulas.
Finally, we outline hot topics in copulas with a special focus on model selection and
goodness-of-fit testing
The numerical approach to quantum field theory in a non-commutative space
Numerical simulation is an important non-perturbative tool to study quantum
field theories defined in non-commutative spaces. In this contribution, a
selection of results from Monte Carlo calculations for non-commutative models
is presented, and their implications are reviewed. In addition, we also discuss
how related numerical techniques have been recently applied in computer
simulations of dimensionally reduced supersymmetric theories.Comment: 15 pages, 6 figures, invited talk presented at the Humboldt Kolleg
"Open Problems in Theoretical Physics: the Issue of Quantum Space-Time", to
appear in the proceedings of the Corfu Summer Institute 2015 "School and
Workshops on Elementary Particle Physics and Gravity" (Corfu, Greece, 1-27
September 2015
Magnetic Moments of Branes and Giant Gravitons
We study the magnetic analogue of Myers' Dielectric Effect and, in some
cases, relate it to the blowing up of particles into branes, first investigated
by Greevy, Susskind and Toumbas. We show that branes or gravitons in M
theory, moving in a magnetic four-form field strength background expand into a
non-commutative two sphere. Both examples of constant magnetic field and
non-constant fields in curved backgrounds generated by branes are considered.
We find, in all cases, another solution, consisting of a two-brane wrapping a
classical two-sphere, which has all the quantum numbers of the branes.
Motivated by this, we investigate the blowing up of gravitons into branes in
backgrounds different from . We find the phenomenon is quite
general. In many cases with less or even no supersymmetry we find a brane
configuration which has the same quantum numbers and the same energy as a
massless particle in supergravity.Comment: 30 pages, no figures, harvma
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