39 research outputs found
Electron Spectra in the Ionization of Atoms by Neutrinos
For neutrinos of O(10keV) energies, their oscillation lengths are less than a
few hundred meters, thereby suggesting the fascinating idea of oscillation
experiments of small geometrical size. To help evaluating this idea we
calculate the ionization cross sections of H, He, Ne and Xe, using any neutrino
flavor, in the few keV energy range. We find that the atomic ionization cross
sections per electron are always smaller than the neutrino cross sections off
free electrons, approaching it from below as the energy increases to the 100
keV region. At the 10-20 keV range though, atomic binding effects are very
important, particularly for the heavier atoms, inducing a factor of two
reduction of the Xe ionization cross section, compared to the free electron
one.Comment: Typos corrected. Version appeared in Phys. Rev. D70:113008 (2004
Boundary Conditions for NHEK through Effective Action Approach
We study the asymptotic symmetry group(ASG) of the near horizon geometry of
extreme Kerr black hole through the effective action approach developed in
1007.1031. By requiring a finite boundary effective action, we derive a new set
of asymptotic Killing vectors and boundary conditions, which are much more
relaxed than the ones proposed in 0907.0303, and still allow a copy of
conformal group as its ASG. In the covariant formalism, the asymptotic charges
are finite, with the corresponding central charge vanishing. By using the
quasi-local charge and introducing a plausible cut-off, we find that the higher
order terms of the asymptotic Killing vectors, which could not be determined
through the effective action approach, contribute to the central charge as
well. We also show that the boundary conditions suggested in 0809.4266 lead to
a divergent first order boundary effective action.Comment: 16 page
Single Neutralino production at CERN LHC
The common belief that the lightest supersymmetric particle (LSP) might be a
neutralino, providing also the main Dark Matter (DM) component, calls for
maximal detail in the study of the neutralino properties. Motivated by this, we
consider the direct production of a single neutralino \tchi^0_i at a
high/energy hadron collider, focusing on the \tchi^0_1 and \tchi^0_2 cases.
At Born level, the relevant subprocesses are q\bar q\to \tchi^0_i \tilde g,
g q\to \tchi^0_i \tilde q_{L,R} and q\bar q'\to \tchi^0_i\tchi^\pm_j; while
at 1-loop, apart from radiative corrections to these processes, we consider
also gg\to \tchi^0_i\tilde{g}, for which a numerical code named PLATONgluino
is released. The relative importance of these channels turns out to be
extremely model dependent. Combining these results with an analogous study of
the direct \tchi^0_i\tchi^0_j pair production, should help in testing the
SUSY models and the Dark Matter assignment.Comment: 22 pages and 12 figures; version to appear in Phys.Rev.
Strings in Kerr-Newmann Black Holes
We study the evolution of strings in the equatorial plane of a Kerr-Newmann
black hole. Writting the equations of motion and the constraints resulting from
Hamilton's principle, three classes of exact solutions are presented, for a
closed string, encircling the black hole. They all depend on two arbitrary
integration functions and two constants. A process of extracting energy is
examined for the case of one of the three families of solutions. This is the
analog of the Penrose process for the case of a particle.Comment: 14 pages, no figures, LaTeX. To appear in Gen. Rel. Gra
String Tension and the Generation of the Conformal Anomaly
The origin of the string conformal anomaly is studied in detail. We use a
reformulated string Lagrangian which allows to consider the string tension
as a small perturbation. The expansion parameter is the worldsheet
speed of light c, which is proportional to . We examine carefully the
interplay between a null (tensionless) string and a tensionful string which
includes orders and higher. The conformal algebra generated by the
constraints is considered. At the quantum level the normal ordering provides a
central charge proportional to . Thus it is clear that quantum null
strings respect conformal invariance and it is the string tension which
generates the conformal anomaly.Comment: More references are included. Final version, to appear in Phys.Rev.D.
6 pages, LaTex, no figure
A description of the neutralino observables in terms of projectors
Applying Jarlskog's treatment of the CKM matrix, to the neutralino mass
matrix in MSSM for real soft gaugino SUSY breaking and -parameters, we
construct explicit analytical expressions for the four projectors which acting
on any neutralino state project out the mass eigenstates. Analytical
expressions for the neutralino mass eigenvalues in terms of the various SUSY
parameters, are also given. It is shown that these projectors and mass
eigenvalues are sufficient to describe any physical observable involving
neutralinos, to any order of perturbation theory. As an example, the cross section at tree level is given in
terms of these projectors. The expected magnitude of their various matrix
elements in plausible SUSY scenarios is also discussed.Comment: 14 pages, no figures. Version to appear in Phys. Rev. D. e-mail:
[email protected]
Hidden and Generalized Conformal Symmetry of Kerr-Sen Spacetimes
It is recently conjectured that generic non-extremal Kerr black hole could be
holographically dual to a hidden conformal field theory in two dimensions.
Moreover, it is known that there are two CFT duals (pictures) to describe the
charged rotating black holes which correspond to angular momentum and
electric charge of the black hole. Furthermore these two pictures can be
incorporated by the CFT duals (general picture) that are generated by
modular group. The general conformal structure can be
revealed by looking at charged scalar wave equation in some appropriate values
of frequency and charge. In this regard, we consider the wave equation of a
charged massless scalar field in background of Kerr-Sen black hole and show in
the "near region", the wave equation can be reproduced by the Casimir operator
of a local hidden conformal
symmetry. We can find the exact agreement between macroscopic and microscopic
physical quantities like entropy and absorption cross section of scalars for
Kerr-Sen black hole. We then find an extension of vector fields that in turn
yields an extended local family of hidden conformal symmetries, parameterized by one
parameter. For some special values of the parameter, we find a copy of
hidden conformal algebra for the charged
Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole in the strong deflection
limit.Comment: 16 pages, new material and results added, extensive improvements in
interpretation of results, references adde
Exact String Solutions in Nontrivial Backgrounds
We show how the classical string dynamics in -dimensional gravity
background can be reduced to the dynamics of a massless particle constrained on
a certain surface whenever there exists at least one Killing vector for the
background metric. We obtain a number of sufficient conditions, which ensure
the existence of exact solutions to the equations of motion and constraints.
These results are extended to include the Kalb-Ramond background. The
-brane dynamics is also analyzed and exact solutions are found. Finally, we
illustrate our considerations with several examples in different dimensions.
All this also applies to the tensionless strings.Comment: 22 pages, LaTeX, no figures; V2:Comments and references added;
V3:Discussion on the properties of the obtained solutions extended, a
reference and acknowledgment added; V4:The references renumbered, to appear
in Phys Rev.
METHODS OF BIOMETRICAL DIAGNOSTICS IN TRANSVERSAL DIRECTION IN PATIENTS WITH MESOGNATHIC TYPE OF DENTAL ARCHES
Aim. A comparative analysis of the horizontal parameters of mesognathic dental arches by the method of Pont and Linder-Harth. Materials and methods. The materials of the research were the results of measurements of diagnostic gypsum models of dental rows of 117 people aged 18-25 with a complete set of permanent teeth, physiological occlusion, mesognathic type of dental arches and various types of dental system. Measurement and calculation of the parameters of the dental arches in the transversal direction were carried out using the methods of Pont and Linder-Harth. Gnathic variants (mesognathy, dolichognathy, brachygnathy) of dental arches (Dmitrienko S.V., 2015) were determined taking into account the dental index calculated as the ratio of the half sum of the width of the crowns of 14 teeth to the width of the dental arch between the second molars. The types of the dental system (normodontia, macrodontia, microdontia) were determined from the summation of the width of the crowns of the upper teeth. Results. Biometric diagnostics of 117 pairs of gypsum models of dentition made it possible to establish that the methods of Pont and Linder-Harth are acceptable for the study of mesognathic dental arches as an estimate of transverse dimensions. There was no significant difference between the calculated indices and actual sizes in patients with mesognathic dental arches and various types of dental system, both in the premolar region and in the molar region. The size of the teeth is of decisive importance for the evaluation of the width of the dental arches of the mesognathic type. Conclusion. Optimization of medical and diagnostic measures in the clinic of orthodontics and orthopedic dentistry in the management of adult patients with dental-jaw pathology provides for the improvement of anthropometric studies, as well as the advisability of reviewing the conventional diagnostic regimens when studying the shape and size of dental arches to predict positive long-term results. Mathematically derived dependences of dental types of dental arches from their transversal parameters are informative, diagnostically significant values that can be used to predict the shape and size of dental arches in the treatment of patients with dentoalveolar anomalies in order to achieve an optimal functional and aesthetic result. The use of the Pont and Linder-Harth method in the analysis of the mesognathic dental arches has no significant errors, and can be used at the stages of diagnosis of shape and size anomalies in the transverse direction
Hawking Radiation of Black Holes in Infrared Modified Ho\v{r}ava-Lifshitz Gravity
We study the Hawking radiation of the spherically symmetric, asymptotically
flat black holes in the infrared modified Horava-Lifshitz gravity by applying
the methods of covariant anomaly cancellation and effective action, as well as
the approach of Damour-Ruffini-Sannan's. These black holes behave as the usual
Schwarzschild ones of the general relativity when the radial distance is very
large. We also extend the method of covariant anomaly cancellation to derive
the Hawking temperature of the spherically symmetric, asymptotically AdS black
holes that represent the analogues of the Schwarzschild AdS ones.Comment: no figures, 16 pages,accepted by EPJ