3,270 research outputs found
On Time-Space Noncommutativity for Transition Processes and Noncommutative Symmetries
We explore the consequences of time-space noncommutativity in the quantum
mechanics of atoms and molecules, focusing on the Moyal plane with just
time-space noncommutativity (,
\theta_{0i}\neqq 0, ). Space rotations and parity are not
automorphisms of this algebra and are not symmetries of quantum physics. Still,
when there are spectral degeneracies of a time-independent Hamiltonian on a
commutative space-time which are due to symmetries, they persist when
\theta_{0i}\neqq 0; they do not depend at all on . They give no
clue about rotation and parity violation when \theta_{0i}\neqq 0. The
persistence of degeneracies for \theta_{0i}\neqq 0 can be understood in terms
of invariance under deformed noncommutative ``rotations'' and ``parity''. They
are not spatial rotations and reflection. We explain such deformed symmetries.
We emphasize the significance of time-dependent perturbations (for example, due
to time-dependent electromagnetic fields) to observe noncommutativity. The
formalism for treating transition processes is illustrated by the example of
nonrelativistic hydrogen atom interacting with quantized electromagnetic field.
In the tree approximation, the transition for hydrogen is
zero in the commutative case. As an example, we show that it is zero in the
same approximation for . The importance of the deformed
rotational symmetry is commented upon further using the decay
as an example.Comment: 13 pages, revised version, references adde
Noncommutative QED and the Lifetimes of Ortho and Para Positronium
We examine the implications of including corrections associated with the
noncommutative extension of quantum electrodynamics - NCQED - to the decays of
the ortho and para positronium (\Trip and \Sing) ground states. In NCQED, the
well known charge conjugation argument restricting \Trip decays to an odd
number of photons and \Sing decays to an even number of photons no longer
obtains. Instead, the dominant two photon decay mode of \Sing is accompanied by
a three photon mode. The dominant three photon decay mode of \Trip receives a
NCQED correction, but there is no corresponding two photon decay mode in the
weak binding limit. These corrections to the three photon decay mode have
a different energy distribution, but their effect is too small to explain any
discrepancy between the observed and calculated values of the \Trip lifetime.Comment: Additional reference
Lepton Flavor Violation at the LHC
Recent results from Super Kamiokande suggest mixing and
hence lepton flavor violation. In supersymmetric models, this flavor violation
may have implications for the pattern of slepton masses and mixings. Possible
signals for this mixing in the decays of sleptons produced at the LHC are
discussed. The sensitivity expected is compared to that of rare decays such as
.Comment: 14 pages, 9 figure
Scaling of space and timelike response of confined relativistic particles
The response of a relativistic particle bound in a linear confining well is
calculated as a function of the momentum and energy transfer, q, \nu. At large
values of |q| the response exhibits scaling in the variable y=\nu-|q|, which is
proportional to the Nachtmann variable, \xi. The approach to scaling is studied
at smaller values of |q|. Scaling occurs at \nu~|q| at relatively small |q|,
and its validity extends over the entire \xi range as |q| increases; this
behavior is observed in electron-proton scattering. About 10% of the response
at large |q| is in the timelike region where \nu>|q|, and it is necessary to
include it to fulfill the particle number sum rule. The Gross-Llewellyn Smith
and Gottfried sum rules are discussed in the context of these results.Comment: 10 pages, 5 figures; submitted to Physics Letters
Noncommutative QCD corrections to the gluonic decays of heavy quarkonia
We compute the Noncommutative QCD (NCQCD) contributions to the three gluon
decay modes of heavy quarkonia. For triplet quarkonia (ortho-quarkonia), the
NCQCD correction to the QCD three gluon decay mode, like the standard model
contribution, is infrared finite. In the case of singlet quarkonia
(para-quarkonia), whose QCD three gluon decay mode has infrared singularities
which are removed using one-loop corrections to the two gluon mode, we find
that NCQCD contribution is also infrared finite. The calculations are performed
in the weak binding limit and do not require the introduction of additional
effective couplings.Comment: Version accepted for publicatio
Test of lepton flavour violation at LHC
We study lepton flavour violating decays of neutralinos and sleptons within
the Minimal Supersymmetric Standard Model, assuming two and three generation
mixings in the slepton sector. We take into account the most recent bounds on
flavour violating rare lepton decays. Taking the SPS1a' scenario as an example,
we show that some of the lepton flavour violating branching ratios of
neutralinos and sleptons can be sizable (~ 5-10%). We study the impact of the
lepton flavour violating neutralino and slepton decays on the di-lepton mass
distributions measured at LHC. We find that they can result in novel and
characteristic edge structures in the distributions. In particular, double-edge
structures can appear in the e tau and mu tau mass spectra if ~tau_1 is the
lightest slepton. The appearance of these remarkable structures provides a
powerful test of supersymmetric lepton flavour violation at LHC.Comment: 15 page
R-parity-violating SUSY and CP violation in B --> phi K_s
Recent measurements of CP asymmetry in B --> phi K_S appear to be
inconsistent with Standard Model expectations. We explore the effect of
R-parity-violating SUSY to understand the data.Comment: Equations corrected. Conclusions unchanged. Latex, 6 pages, one fi
Noncommutative electrodynamics and ultra high energy gamma rays
Plane waves in noncommutative classical electrodynamics (NCED) have a
peculiar dispersion relation. We investigate the kinematical conditions on this
deformed "mass shell" which come from ultra high energy gamma rays and discuss
noncommutative dynamical effects on the gamma absorption by the infrared
background and on the intrinsic spectrum. Finally we note that in NCED there is
a strong correlation between the modified dispersion relation and the presence
of dynamical effects in electromagnetic phenomena such as in the case of the
synchrotron radiation. From this point of view, the limits on the typical
energy scale of the violation of Lorentz invariance obtained by deformed
dispersion relations and by assuming undeformed dynamical effects should be
taken with some caution.Comment: Latex file, 7 pages, to be published in Europhysics Letter
- …