987 research outputs found
CP, T and CPT Violations in the K^0 - bar{K^0} System -- Present Status --
Possible violation of CP, T and CPT symmetries in the K^0 - bar{K^0} system
is studied in a way as phenomenological and comprehensive as possible. For this
purpose, we first introduce parameters which represent violation of these
symmetries in mixing parameters and decay amplitudes in a convenient and
well-defined way and, treating these parameters as small, derive formulas which
relate them to the experimentally measured quantities. We then perform
numerical analyses to derive constraints to these symmetry-violating
parameters, with the latest data reported by KTeV Collaboration, NA48
Collaboration and CPLEAR Collaboration, along with those compiled by Particle
Data Group, used as inputs. The result obtained by CPLEAR Collaboration from an
unconstrained fit to a time-dependent leptonic asymmetry, aided by the
Bell-Steinberger relation, enables us to determine or constrain most of the
parameters separately. It is shown among the other things that (1) CP and T
symmetries are violated definitively at least at the level of 10^{-4} in 2 pi
decays, (2) CP and T symmetries are violated at least at the level of 10^{-3}
in the K^0 - bar{K^0} mixing, and (3) CPT symmetry is at present tested to the
level of 10^{-5} at the utmost.Comment: 20 page
Thin current sheets in the magnetotail at lunar distances: statistics of ARTEMIS observations
The magnetotail current sheet's spatial configuration and stability control
the onset of magnetic reconnection - the driving process for magnetospheric
substorms. The near-Earth current sheet has been thoroughly investigated by
numerous missions, whereas the midtail current sheet has not been adequately
explored. This is especially the case for the long-term variation of its
configuration in response to the solar wind. We present a statistical analysis
of 1261 magnetotail current sheet crossings by the Acceleration, Reconnection,
Turbulence and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS)
mission orbiting the moon (X~-60 RE), collected during the entirety of Solar
Cycle 24. We demonstrate that the magnetotail current sheet typically remains
extremely thin, with a characteristic thickness comparable to the thermal ion
gyroradius, even at such large distances from Earth's dipole. We also find that
a substantial fraction (~one quarter) of the observed current sheets have a
partially force-free magnetic field configuration, with a negligible
contribution of the thermal pressure and a significant contribution of the
magnetic field shear component to the pressure balance. Further, we quantify
the impact of the changing solar wind driving conditions on the properties of
the midtail around the lunar orbit. During active solar wind driving
conditions, we observe an increase in the occurrence rate of thin current
sheets, whereas quiet solar wind driving conditions seem to favor the formation
of partially force-free current sheets
Considerations on Super Poincare Algebras and their Extensions to Simple Superalgebras
We consider simple superalgebras which are a supersymmetric extension of
\fspin(s,t) in the cases where the number of odd generators does not exceed
64. All of them contain a super Poincar\'e algebra as a contraction and another
as a subalgebra. Because of the contraction property, some of these algebras
can be interpreted as de Sitter or anti de Sitter superalgebras. However, the
number of odd generators present in the contraction is not always minimal due
to the different splitting properties of the spinor representations under a
subalgebra. We consider the general case, with arbitrary dimension and
signature, and examine in detail particular examples with physical implications
in dimensions and .Comment: 16 pages, AMS-LaTeX. Version to appear in the Reviews in Mathematical
Physic
On the formation of tilted flux ropes in the Earth's magnetotail observed with ARTEMIS
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95540/1/jgra21806.pd
On Conceptually Simple Algorithms for Variants of Online Bipartite Matching
We present a series of results regarding conceptually simple algorithms for
bipartite matching in various online and related models. We first consider a
deterministic adversarial model. The best approximation ratio possible for a
one-pass deterministic online algorithm is , which is achieved by any
greedy algorithm. D\"urr et al. recently presented a -pass algorithm called
Category-Advice that achieves approximation ratio . We extend their
algorithm to multiple passes. We prove the exact approximation ratio for the
-pass Category-Advice algorithm for all , and show that the
approximation ratio converges to the inverse of the golden ratio
as goes to infinity. The convergence is
extremely fast --- the -pass Category-Advice algorithm is already within
of the inverse of the golden ratio.
We then consider a natural greedy algorithm in the online stochastic IID
model---MinDegree. This algorithm is an online version of a well-known and
extensively studied offline algorithm MinGreedy. We show that MinDegree cannot
achieve an approximation ratio better than , which is guaranteed by any
consistent greedy algorithm in the known IID model.
Finally, following the work in Besser and Poloczek, we depart from an
adversarial or stochastic ordering and investigate a natural randomized
algorithm (MinRanking) in the priority model. Although the priority model
allows the algorithm to choose the input ordering in a general but well defined
way, this natural algorithm cannot obtain the approximation of the Ranking
algorithm in the ROM model
Constraints on a Parity-Conserving/Time-Reversal-Non-Conserving Interaction
Time-Reversal-Invariance non-conservation has now been unequivocally
demonstrated in a direct measurement at CPLEAR. What about tests of
time-reversal-invariance in systems other than the kaon system? Tests of
time-reversal-invariance belong to two classes: searches for parity violating
(P-odd)/time-reversal-invariance-odd (T-odd) interactions, and for P-even/T-odd
interactions (assuming CPT conservation this implies C-conjugation
non-conservation). Limits on a P-odd/T-odd interaction follow from measurements
of the electric dipole moment of the neutron (with a present upper limit of 6 x
10^-26 e.cm [95% C.L.]). It provides a limit on a P-odd/T-odd pion-nucleon
coupling constant which is less than 10^-4 times the weak interaction strength.
Experimental limits on a P-even/T-odd interaction are much less stringent.
Following the standard approach of describing the nucleon-nucleon interaction
in terms of meson exchanges, it can be shown that only charged rho-meson
exchange and A_1 meson exchange can lead to a P-even/T-odd interaction. The
better constraints stem from measurements of the electric dipole moment of the
neutron and from measurements of charge-symmetry breaking in neutron-proton
elastic scattering. The latter experiments were executed at TRIUMF (497 and 347
MeV) and at IUCF (183 MeV). Weak decay experiments may provide limits which
will possibly be comparable. All other experiments, like gamma decay
experiments, detailed balance experiments, polarization - analyzing power
difference determinations, and five-fold correlation experiments with polarized
incident nucleons and aligned nuclear targets, have been shown to be at least
an order of magnitude less sensitive.Comment: 15 pages LaTeX, including 5 PostScript figures. Uses ijmpe1.sty. To
appear in International Journal of Modern Physics E (IJMPE). Slight change in
short abstrac
On the cause and extent of outer radiation belt losses during the 30 September 2012 dropout event
Abstract On 30 September 2012, a flux dropout occurred throughout Earth\u27s outer electron radiation belt during the main phase of a strong geomagnetic storm. Using eight spacecraft from NASA\u27s Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Van Allen Probes missions and NOAA\u27s Geostationary Operational Environmental Satellites constellation, we examined the full extent and timescales of the dropout based on particle energy, equatorial pitch angle, radial distance, and species. We calculated phase space densities of relativistic electrons, in adiabatic invariant coordinates, which revealed that loss processes during the dropout were \u3e 90% effective throughout the majority of the outer belt and the plasmapause played a key role in limiting the spatial extent of the dropout. THEMIS and the Van Allen Probes observed telltale signatures of loss due to magnetopause shadowing and subsequent outward radial transport, including similar loss of energetic ring current ions. However, Van Allen Probes observations suggest that another loss process played a role for multi-MeV electrons at lower L shells (L\u3c ∼4). Key Points Dropout events can encompass the entire outer radiation belt Dropouts can result in \u3e90% losses and be a hard reset on the system Loss at L \u3e ∼4 is dominated by MP shadowing and outward transport
- …