2,858 research outputs found
Evaporation of (quantum) black holes and energy conservation
We consider Hawking radiation as due to a tunneling process in a black hole
were quantum corrections, derived from Quantum Einstein Gravity, are taken into
account. The consequent derivation, satisfying conservation laws, leads to a
deviation from an exact thermal spectrum. The non-thermal radiation is shown to
carry information out of the black hole. Under the appropriate approximation, a
quantum corrected temperature is assigned to the black hole. The evolution of
the quantum black hole as it evaporates is then described by taking into
account the full implications of energy conservation as well as the
back-scattered radiation. It is shown that, as a critical mass of the order of
Planck's mass is reached, the evaporation process decelerates abruptly while
the black hole mass decays towards this critical mass.Comment: 16 pages, 2 figure
The mechanism why colliders could create quasi-stable black holes
It has been postulated that black holes could be created in particle
collisions within the range of the available energies for nowadays colliders
(LHC). In this paper we analyze the evaporation of a type of black holes that
are candidates for this specific behaviour, namely, small black holes on a
brane in a world with large extra-dimensions. We examine their evolution under
the assumption that energy conservation is satisfied during the process and
compare it with the standard evaporation approach. We claim that, rather than
undergoing a quick total evaporation, black holes become quasi-stable. We
comment on the (absence of) implications for safety of this result. We also
discuss how the presence of black holes together with the correctness of the
energy conservation approach might be experimentally verified.Comment: 16 pages, 3 figure
Second-Order Fermions
It has been proposed several times in the past that one can obtain an
equivalent, but in many aspects simpler description of fermions by first
reformulating their first-order (Dirac) Lagrangian in terms of two-component
spinors, and then integrating out the spinors of one chirality ( primed
or dotted). The resulting new Lagrangian is second-order in derivatives, and
contains two-component spinors of only one chirality. The new second-order
formulation simplifies the fermion Feynman rules of the theory considerably,
the propagator becomes a multiple of an identity matrix in the field
space. The aim of this thesis is to work out the details of this formulation
for theories such as Quantum Electrodynamics, and the Standard Model of
elementary particles. After having developed the tools necessary to establish
the second-order formalism as an equivalent approach to spinor field theories,
we proceed with some important consistency checks that the new formulation is
required to pass, namely the presence or absence of anomalies in their
perturbative and non-perturbative description, and the unitarity of the
S-Matrix derived from their Lagrangian. Another aspect which is studied is
unification, where we seek novel gauge-groups that can be used to embed all of
the Standard Model content: forces and fermionic representations. Finally, we
will explore the possibility to unify gravity and the Standard Model when the
former is seen as a diffeomorphism invariant gauge-theory.Comment: Ph.D. Thesis, 281p
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