17,615 research outputs found
Neutrino oscillations and Lorentz Invariance Violation in a Finslerian Geometrical model
Neutrino oscillations are one of the first evidences of physics beyond the
Standard Model (SM). Since Lorentz Invariance is a fundamental symmetry of the
SM, recently also neutrino physics has been explored to verify the eventual
modification of this symmetry and its potential magnitude. In this work we
study the consequences of the introduction of Lorentz Invariance Violation
(LIV) in the high energy neutrinos propagation and evaluate the impact of this
eventual violation on the oscillation predictions. An effective theory
explaining these physical effects is introduced via Modified Dispersion
Relations. This approach, originally introduced by Coleman and Glashow,
corresponds in our model to a modification of the special relativity geometry.
Moreover, the generalization of this perspective leads to the introduction of a
maximum attainable velocity which is specific of the particle. This can be
formalized in Finsler geometry, a more general theory of space-time. In the
present paper the impact of this kind of LIV on neutrino phenomenology is
studied, in particular by analyzing the corrections introduced in neutrino
oscillation probabilities for different values of neutrino energies and
baselines of experimental interest. The possibility of further improving the
present constraints on CPT-even LIV coefficients by means of our analysis is
also discussed.Comment: Accepted for publication with minor revisions, will appear on
European Physics Journal
Solar Neutrinos
The study of solar neutrinos has given since ever a fundamental contribution
both to astroparticle and to elementary particle physics, offering an ideal
test of solar models and offering at the same time relevant indications on the
fundamental interactions among particles. After reviewing the striking results
of the last two decades, which were determinant to solve the long standing
solar neutrino puzzle and refine the Standard Solar Model, we focus our
attention on the more recent results in this field and on the experiments
presently running or planned for the near future. The main focus at the moment
is to improve the knowledge of the mass and mixing pattern and especially to
study in detail the lowest energy part of the spectrum, which represents most
of solar neutrino spectrum but is still a partially unexplored realm. We
discuss this research project and the way in which present and future
experiments could contribute to make the theoretical framemork more complete
and stable, understanding the origin of some "anomalies" that seem to emerge
from the data and contributing to answer some present questions, like the exact
mechanism of the vacuum to matter transition and the solution of the so called
solar metallicity problem.Comment: 51 pages, to be published in Special Issue on Neutrino Physics,
Advances in High Energy Physics Hindawi Publishing Corporation 201
A New Basis for QED Bound State Computations
A simple method to compute QED bound state properties is presented, in which
binding energy effects are treated non-perturbatively. It is shown that to take
the effects of all ladder Coulomb photon exchanges into account, one can simply
perform the derivative of standard QED amplitudes with respect to the external
momentum. For example, the derivative of the light-by-light scattering
amplitude gives an amplitude for orthopositronium decay to three photons where
any number of Coulomb photon exchanges between the e-e+ is included.
Various applications are presented. From them, it is shown that binding
energy must be treated non-perturbatively in order to preserve the analyticity
of positronium decay amplitudes.
Interesting perspectives for quarkonium physics are briefly sketched.Comment: LaTeX, 23 pages, 16 figures. Minor corrections. Some comments adde
Weak solutions to problems involving inviscid fluids
We consider an abstract functional-differential equation derived from the
pressure-less Euler system with variable coefficients that includes several
systems of partial differential equations arising in the fluid mechanics. Using
the method of convex integration we show the existence of infinitely many weak
solutions for prescribed initial data and kinetic energy
Calibrated American option pricing by stochastic linear programming
Cataloged from PDF version of article.We propose an approach for computing the arbitrage-free interval for the price of an American option in discrete incomplete market models via linear programming. The main idea is built replicating strategies that use both the basic asset and some European derivatives available on the market for trading. This method goes under the name of calibrated option pricing and it has given significant results for
European options. Here, we extend the analysis to American options showing that
the arbitrage-free interval can be characterized in terms of martingale measures
and that it gets significantly reduced with respect to the non-calibrated case
Sifting the Network: Performing Packet Triage with NFR
We describe a set of Network Flight Recorder scripts designed to detect network intrusions. After developing scripts that detect some known attacks, we focus on sifting scripts that attempt to remove "normal" traffic from a packet stream, leaving behind fewer packets requiring manual inspection. We conclude with a description of our experiences with the NFR product.http://deepblue.lib.umich.edu/bitstream/2027.42/107922/1/citi-tr-98-6.pd
Positronium Decay : Gauge Invariance and Analyticity
The construction of positronium decay amplitudes is handled through the use
of dispersion relations. In this way, emphasis is put on basic QED principles:
gauge invariance and soft-photon limits (analyticity).
A firm grounding is given to the factorization approaches, and some
ambiguities in the spin and energy structures of the positronium wavefunction
are removed. Non-factorizable amplitudes are naturally introduced. Their
dynamics is described, especially regarding the enforcement of gauge invariance
and analyticity through delicate interferences. The important question of the
completeness of the present theoretical predictions for the decay rates is then
addressed. Indeed, some of those non-factorizable contributions are unaccounted
for by NRQED analyses. However, it is shown that such new contributions are
highly suppressed, being of order alpha^3.
Finally, a particular effective form factor formalism is constructed for
parapositronium, allowing a thorough analysis of binding energy effects and
analyticity implementation.Comment: 34 pages, 13 figure
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