737 research outputs found
Naked Singularity in a Modified Gravity Theory
The cosmological constant induced by quantum fluctuation of the graviton on a
given background is considered as a tool for building a spectrum of different
geometries. In particular, we apply the method to the Schwarzschild background
with positive and negative mass parameter. In this way, we put on the same
level of comparison the related naked singularity (-M) and the positive mass
wormhole. We discuss how to extract information in the context of a f(R)
theory. We use the Wheeler-De Witt equation as a basic equation to perform such
an analysis regarded as a Sturm-Liouville problem . The application of the same
procedure used for the ordinary theory, namely f(R)=R, reveals that to this
approximation level, it is not possible to classify the Schwarzschild and its
naked partner into a geometry spectrum.Comment: 8 Pages. Contribution given to DICE 2008. To appear in the
proceeding
The Cosmological Constant as an Eigenvalue of a Sturm-Liouville Problem and its Renormalization
We discuss the case of massive gravitons and their relation with the
cosmological constant, considered as an eigenvalue of a Sturm-Liouville
problem. A variational approach with Gaussian trial wave functionals is used as
a method to study such a problem. We approximate the equation to one loop in a
Schwarzschild background and a zeta function regularization is involved to
handle with divergences. The regularization is closely related to the
subtraction procedure appearing in the computation of Casimir energy in a
curved background. A renormalization procedure is introduced to remove the
infinities together with a renormalization group equation.Comment: 8 pages, Talk given at "QFEXT'05", the 7-th workshop on quantum field
theory under the influence of external conditions, Barcelona, Spain, Sept.
5-9, 200
Casimir energy and black hole pair creation in Schwarzschild-de Sitter spacetime
Following the subtraction procedure for manifolds with boundaries, we
calculate by variational methods, the Schwarzschild-de Sitter and the de Sitter
space energy difference. By computing the one loop approximation for TT tensors
we discover the existence of an unstable mode even for the non-degenerate case.
This result seems to be in agreement with the sub-maximal black hole pair
creation of Bousso-Hawking. The instability can be eliminated by the boundary
reduction method. Implications on a foam-like space are discussed.Comment: 19 pages,RevTeX with package epsf and four eps figures. Added other
references. Accepted for publication in Classical and Quantum Gravit
Extracting the Cosmological Constant from the Wheeler DeWitt Equation in a Modified Gravity Theory
We discuss how to extract information about the cosmological constant from
the Wheeler-DeWitt equation, considered as an eigenvalue of a Sturm-Liouville
problem. A generalization to a f(R)theory is taken under examination. The
equation is approximated to one loop with the help of a variational approach
with Gaussian trial wave functionals. We use a zeta function regularization to
handle with divergences. A renormalization procedure is introduced to remove
the infinities together with a renormalization group equation.Comment: Talk given at QFEXT 07, Workshop on Quantum Field Theory Under the
Influence of External Conditions, Leipzig, 17-21 Sep 2007 and talk given at
9th International Conference on Path Integrals - New Trends and Perspectives,
Dresden, 23-28 September 2007. 8 pages, accepted for publication in Journal
of Physics
Area spectrum and quasinormal modes of black holes
We demonstrate that an equidistant area spectrum for the link variables in
loop quantum gravity can reproduce both the thermodynamics and the quasinormal
mode properties of black holes.Comment: 11 pages, no figures; references adde
Farmaci orfani e malattie rare: un confronto internazionale delle normative di riferimento
Orphan drugs are defined as medicines with low economic returns, so that their production is not a profitable business far pharmaceutical companies. The present study analyses the main characteristics and the role of orphan drugs in four countries (United States of America, .Japan, Australia and European Union), by considering the regulation and the market situation of each State. All countries have introduced a specific legislation on orphan drugs to stimulate the research activity of pharmaceutical industry. The first law was the Orphan Drug Act of the United States of America in 1982. A common limit of all regulations is the strict correlation between “orphan drugs” and “rare diseases”. In fact, the term “orphan” does not refer only to rare disease, but also to other elements that can determine low economic returns for the industry (e.g. drugs with high cost of research and development, drugs that cannot be patented)
Commissioning and operation of the Cherenkov detector for proton Flux Measurement of the UA9 Experiment
The UA9 Experiment at CERN-SPS investigates channeling processes in bent
silicon crystals with the aim to manipulate hadron beams. Monitoring and
characterization of channeled beams in the high energy accelerators environment
ideally requires in-vacuum and radiation hard detectors. For this purpose the
Cherenkov detector for proton Flux Measurement (CpFM) was designed and
developed. It is based on thin fused silica bars in the beam pipe vacuum which
intercept charged particles and generate Cherenkov light. The first version of
the CpFM is installed since 2015 in the crystal-assisted collimation setup of
the UA9 experiment. In this paper the procedures to make the detector
operational and fully integrated in the UA9 setup are described. The most
important standard operations of the detector are presented. They have been
used to commission and characterize the detector, providing moreover the
measurement of the integrated channeled beam profile and several functionality
tests as the determination of the crystal bending angle.
The calibration has been performed with Lead (Pb) and Xenon (Xe) beams and
the results are applied to the flux measurement discussed here in detail.Comment: 25 pages, 14 figure
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