5,576 research outputs found
Flow of entropy in the evolution of the B^0 anti B^0 system: Upper bound on CP violation from unidirectionality
We have previously studied the time-dependence of a B anti B meson mixture in
terms of its density matrix. The requirement that the absolute value of the
Stokes vector zeta(t) should evolve monotonically from its initial value
zeta(0)=0 to its final value zeta(infinity)=1 was shown to lead to an upper
bound on the CP violating overlap . In the present note we consider an
entropy variable S as an alternative measure of mixing. We show that exactly
the same upper bound emerges from the requirement that the flow of entropy is
unidirectional (dS/dt<0). We compare the entropic current dS/dt with and
without CP violation and identify certain physical features that appear when
the bound on is violated.Comment: 8 pages, 4 figures. Typos corrected, comment on entropy added. To be
published in Physical Review
An upper limit on CP violation in the system
In a previous publication we noted that the time dependence of an incoherent
mixture undergoes a qualitative change when the magnitude of CP
violation exceeds a critical value. Requiring, on physical grounds,
that the system evolve from an initial incoherent state to a final pure state
in a monotonic way, yields a new upper limit for . The recent
measurement of the wrong charge semileptonic asymmetry of mesons
presented by the D0 collaboration is outside this bound by one standard
deviation. If this result is confirmed it implies the existence of a new
quantum mechanical oscillation phenomenon.Comment: 7 pages, 2 figures, version submitted for publication (Physical
Review
The Mellin Transform Technique for the Extraction of the Gluon Density
A new method is presented to determine the gluon density in the proton from
jet production in deeply inelastic scattering. By using the technique of Mellin
transforms not only for the solution of the scale evolution equation of the
parton densities but also for the evaluation of scattering cross sections, the
gluon density can be extracted in next-to-leading order QCD. The method
described in this paper is, however, more general, and can be used in
situations where a repeated fast numerical evaluation of scattering cross
sections for varying parton distribution functions is required.Comment: 13 pages (LaTeX); 2 figures are included via epsfig; the
corresponding postscript files are uuencode
CP Violation and Arrows of Time Evolution of a Neutral or Meson from an Incoherent to a Coherent State
We study the evolution of a neutral meson prepared as an incoherent equal
mixture of and . Denoting the density matrix by \rho(t) =
{1/2} N(t) [\1 + \vec{\zeta}(t) \cdot \vec{\sigma} ] , the norm of the state
is found to decrease monotonically from one to zero, while the magnitude
of the Stokes vector increases monotonically from zero to
one. This property qualifies these observables as arrows of time. Requiring
monotonic behaviour of for arbitrary values of and
yields a bound on the CP-violating overlap , which is similar to, but weaker than, the known unitarity
bound. A similar requirement on yields a new bound,
which is particularly effective in limiting
the CP-violating overlap in the - system. We obtain the Stokes
parameter which shows how the average strangeness of the beam
evolves from zero to . The evolution of the Stokes vector from
to has a resemblance to an order
parameter of a system undergoing spontaneous symmetry breaking.Comment: 13 pages, 6 figures. Inserted conon "." in title; minor change in
text. To appear in Physical review
Lepton Mass Effects in Single Pion Production by Neutrinos
We reconsider the Feynman-Kislinger-Ravndal model applied to
neutrino-excitation of baryon resonances. The effects of lepton mass are
included, using the formalism of Kuzmin, Lyubushkin and Naumov. In addition we
take account of the pion-pole contribution to the hadronic axial vector
current. Application of this new formalism to the reaction nu(mu) + p --> mu +
Delta at E(nu) approx 1 GeV gives a suppressed cross section at small angles,
in agreement with the screening correction in Adler's forward scattering
theorem. Application to the process nu(tau) + p --> tau + Delta at E(nu) approx
7 GeV leads to the prediction of right-handed tau polarization for
forward-going leptons, in line with a calculation based on an isobar model. Our
formalism represents an improved version of the Rein-Sehgal model,
incorporating lepton mass effects in a manner consistent with PCAC.Comment: 14 pages, 5 figures. Typos in eq. 9 and 27 corrected. Numbers in
table I for coherent cross sections (RSA and RSC) corrected (normalization
error). Figs 3 and 4 changed accordingly. These corrections also apply to the
published version PRD 76, 113004 (2007
PCAC and coherent pion production by low energy neutrinos
Coherent pi^+ and pi^0 production in low energy neutrino reactions is
discussed in the framework of the partially conserved axial vector current
theory (PCAC). The role of lepton mass effects in suppressing the pi^+
production is emphasized. Instead of using models of pion nucleus scattering,
the available data on pion Carbon scattering are implemented for an analysis of
the PCAC prediction. Our results agree well with the published upper limits for
pi^+ production but are much below the recent MiniBooNE result for pi^0
production.Comment: 9 pages, 4 figures New reference added. Comment to fig. 1b and to
ref. 16 added. Typos corrected. Version corresponds to the one submitted to
Phys. Rev.
Phenomenology of the Gowdy Universe on
Numerical studies of the plane symmetric, vacuum Gowdy universe on yield strong support for the conjectured asymptotically velocity term
dominated (AVTD) behavior of its evolution toward the singularity except,
perhaps, at isolated spatial points. A generic solution is characterized by
spiky features and apparent ``discontinuities'' in the wave amplitudes. It is
shown that the nonlinear terms in the wave equations drive the system
generically to the ``small velocity'' AVTD regime and that the spiky features
are caused by the absence of these terms at isolated spatial points.Comment: 19 pages, 21 figures, uses Revtex, psfi
Vermeer intermedial! Überlegungen zur Popularität seiner Gemälde in zeitgenössischen Erzähltexten
Zusammenfassung
Das facettenreiche Potential intermedialer Verstrickungen von Malerei und Literatur zeigt sich anhand unterschiedlichster Ausdrucksformen. Gemälde fungieren als Motiv in Theater und Film, werden nachgestellt und fotografiert oder es wird auf sie Bezug genommen. Besonders häufig sind Rekurse vonseiten der erzählenden Literatur zu beobachten. Dabei fällt auf, dass in den Neuerscheinungen der letzten Jahre verhältnismäßig oft Gemälde des holländischen Malers Jan Vermeer verarbeitet wurden. Die Gründe dafür werden in inhaltlichen und formalen Besonderheiten seiner Gemäldekonzeption gesucht und sollen kurz skizziert werden
STM microscopy of the CDW in 1T-TiSe2 in the presence of single atom defects
We present a detailed low temperature scanning tunneling microscopy study of
the commensurate charge density wave (CDW) in 1-TiSe in the presence of
single atom defects. We find no significant modification of the CDW lattice in
single crystals with native defects concentrations where some bulk probes
already measure substantial reductions in the CDW phase transition signature.
Systematic analysis of STM micrographs combined with density functional theory
modelling of atomic defect patterns indicate that the observed CDW modulation
lies in the Se surface layer. The defect patterns clearly show there are no
2-polytype inclusions in the CDW phase, as previously found at room
temperature [Titov A.N. et al, Phys. Sol. State 53, 1073 (2011). They further
provide an alternative explanation for the chiral Friedel oscillations recently
reported in this compound [J. Ishioka et al., Phys. Rev. B 84, 245125, (2011)].Comment: 5 pages, 4 figure
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