328 research outputs found
Charm nonleptonic decays and final state interactions
A global previous analysis of two-body nonleptonic decays of mesons has
been extended to the decays involving light scalar mesons. The allowance for
final state interaction also in nonresonant channels provides a fit of much
improved quality and with less symmetry breaking in the axial charges. We give
predictions for about 50 decay branching ratios yet to be measured. We also
discuss long distance contributions to the difference between
the and widths.Comment: 14 pages, no figures, plain TeX, uses harvmac.tex and tables.te
Intermediate Symmetries in the Spontaneous Breaking of Supersymmetric SO(10)
We study the supersymmetric spontaneous symmetry breaking of SO(10) into
SU(3)xSU(2)xU(1) for the most physically interesting cases of SU(5) or flipped
SU(5)xU(1) intermediate symmetries. The first case is more easily realized
while the second one requires a fine-tuning condition on the parameters of the
superpotential. This is because in the case of SU(5) symmetry there is at most
one singlet of the residual symmetry in each SO(10) irreducible representation.
We also point out on more general grounds in supersymmetric GUT's that some
intermediate symmetries can be exactly realized and others can only be
approximated by fine-tuning. In the first category, there could occur some
tunneling between the vacua with exact and approximate intermediate symmetry.
The flipped SU(5)xU(1) symmetry improves the unification of gauge couplings if
(B-L) is broken by (B-L)=1 scalars yielding right handed neutrino masses below
10^{14} GeV}.Comment: LaTex, 9 page
CP violating asymmetries in charged D meson decays
The CP violating asymmetries for Cabibbo suppressed charged D meson decays in
the standard model are estimated in the factorized approximation, using the
two-loop effective hamiltonian and a model for final state interactions
previously tested for Cabibbo allowed D decays. No new parameters are added.
The predictions are larger than expected and not too far from the experimental
possibilities.Comment: 13 pages, Roma n. 91
A Selection Rule for Multiquark Decays
By assuming SU(6)_cs symmetry for pentaquark decays one finds a selection
rule, which strongly reduces the number of states able to decay into a baryon
and a meson final state and allows an intriguing identification for the Theta^+
particle recently discovered with the prediction of a narrow width.Comment: 10 pages, no figure
Testing kappa-Poincare' with neutral kaons
In recent work on experimental tests of quantum-gravity-motivated
phenomenological models, a significant role has been played by the so-called
``'' deformations of Poincar\'e symmetries. Sensitivity to values of
the relevant deformation length as small as has
been achieved in recent analyses comparing the structure of -Poincar\'e
symmetries with data on the gamma rays we detect from distant astrophysical
sources. We investigate violations of CPT symmetry which may be associated with
-Poincar\'e in the physics of the neutral-kaon system. A simple
estimate indicates that experiments on the neutral kaons may actually be more
-sensitive than corresponding astrophysical experiments, and may
already allow to probe values of of order the Planck length.Comment: 9 pages, LaTe
Sufficient conditions for the existence of Q-balls in gauge theories
We formulate a set of simple sufficient conditions for the existence of
Q-balls in gauge theories.Comment: 5 page
Uncertainties on the CP Phase \bfalpha due to Penguin Diagrams
A major problem in the determination of the the CP angle , that
should be measured through modes of the type is the uncertainty coming from Penguin diagrams. We consider the
different ground state modes , , , and, assuming
the FSI phases to be negligible, we investigate the amount of uncertainty
coming from Penguins that can be parametrized by a dilution factor and an
angle shift . The parameter is either 1 or very close to 1
in all these modes, and it can be measured independently, up to a sign
ambiguity, by the dependence. Assuming factorization, we show that is much smaller for the modes and than for , and we plot their allowed region as a function of itself.
Moreover, we show that most of the modes contribute to the asymmetry with the
same sign, and define for their sum an effective and an effective
, an average of for the different modes.
It turns out that is of the order of 0.9, is
between 5 and 10 and, relative to , the statistical gain for
the sum is of about a factor 10. Finally, we compute the ratios that test the strength of the Penguins and depend on the CP angles,
as emphasized by Silva and Wolfenstein and by Deandrea et al.Comment: 18 page
Tool support for verifying applications using object-oriented patterns
Applying design patterns is considered a helpful technique for designing software systems.
Patterns description, however, results not sufficiently precise providing a weak understanding and making it difficult to be certain when a pattern is being used correctly. We have formally specified properties of patterns and a formal basis for object-oriented design. In the present work, our formal basis is used as a support to an automatic tool for verifying proper applications of patterns. The usage of this tool is mainly focused on the learning process about patterns applications. Through a better understanding of patterns, the designer may certify when and how a pattern is being appropriately applied to solve a specific design problem. Furthermore, the whole design process could be improved by using a precise technique supported by an automatic tool for verification.Eje: Ingeniería de Software y Base de DatosRed de Universidades con Carreras en Informática (RedUNCI
Quantum Effects in Friedmann-Robertson-Walker Cosmologies
Electrodynamics for self-interacting scalar fields in spatially flat
Friedmann-Robertson-Walker space-times is studied. The corresponding one-loop
field equation for the expectation value of the complex scalar field in the
conformal vacuum is derived. For exponentially expanding universes, the
equations for the Bogoliubov coefficients describing the coupling of the scalar
field to gravity are solved numerically. They yield a non-local correction to
the Coleman-Weinberg effective potential which does not modify the pattern of
minima found in static de Sitter space. Such a correction contains a
dissipative term which, accounting for the decay of the classical configuration
in scalar field quanta, may be relevant for the reheating stage. The physical
meaning of the non-local term in the semiclassical field equation is
investigated by evaluating this contribution for various background field
configurations.Comment: 17 pages, plain TeX + 5 uuencoded figure
Recursive Selective Harmonic Elimination for Multilevel Inverters: Mathematical Formulation and Experimental Validation
A recursive method that eliminates +1 harmonics and their respective multiples from the output voltage of a cascaded H-bridge multilevel inverters with = 2 dc sources ( = 1, 2, 3,...) is proposed. It solves 2×2 linear systems with not singular matrices and always gives an exact solution with very low computational effort. Simulated results in three-phase five, nine, seventeen and thirty three level CHB inverters, and experimental results in five-level inverter demonstrate the validity of the method
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