923 research outputs found
Logarithmic deformations of the rational superpotential/Landau-Ginzburg construction of solutions of the WDVV equations
The superpotential in the Landau-Ginzburg construction of solutions to the Witten-Dijkgraaf-Verlinde-Verlinde (or WDVV) equations is modified to include logarithmic terms. This results in deformations - quadratic in the deformation parameters- of the normal prepotential solutions of the WDVV equations. Such solutions satisfy various pseudo-quasi-homogeneity conditions, on assigning a notional weight to the deformation parameters. These solutions originate in the so-called `water-bag' reductions of the dispersionless KP hierarchy. This construction includes, as a special case, deformations which are polynomial in the flat coordinates, resulting in a new class of polynomial solutions of the WDVV equations
Coisotropic deformations of associative algebras and dispersionless integrable hierarchies
The paper is an inquiry of the algebraic foundations of the theory of
dispersionless integrable hierarchies, like the dispersionless KP and modified
KP hierarchies and the universal Whitham's hierarchy of genus zero. It stands
out for the idea of interpreting these hierarchies as equations of coisotropic
deformations for the structure constants of certain associative algebras. It
discusses the link between the structure constants and the Hirota's tau
function, and shows that the dispersionless Hirota's bilinear equations are,
within this approach, a way of writing the associativity conditions for the
structure constants in terms of the tau function. It also suggests a simple
interpretation of the algebro-geometric construction of the universal Whitham's
equations of genus zero due to Krichever.Comment: minor misprints correcte
Light-Front Quantisation as an Initial-Boundary Value Problem
In the light front quantisation scheme initial conditions are usually
provided on a single lightlike hyperplane. This, however, is insufficient to
yield a unique solution of the field equations. We investigate under which
additional conditions the problem of solving the field equations becomes well
posed. The consequences for quantisation are studied within a Hamiltonian
formulation by using the method of Faddeev and Jackiw for dealing with
first-order Lagrangians. For the prototype field theory of massive scalar
fields in 1+1 dimensions, we find that initial conditions for fixed light cone
time {\sl and} boundary conditions in the spatial variable are sufficient to
yield a consistent commutator algebra. Data on a second lightlike hyperplane
are not necessary. Hamiltonian and Euler-Lagrange equations of motion become
equivalent; the description of the dynamics remains canonical and simple. In
this way we justify the approach of discretised light cone quantisation.Comment: 26 pages (including figure), tex, figure in latex, TPR 93-
Pair excitations and parameters of state of imbalanced Fermi gases at finite temperatures
The spectra of low-lying pair excitations for an imbalanced two-component
superfluid Fermi gas are analytically derived within the path-integral
formalism taking into account Gaussian fluctuations about the saddle point. The
spectra are obtained for nonzero temperatures, both with and without imbalance,
and for arbitrary interaction strength. On the basis of the pair excitation
spectrum, we have calculated the thermodynamic parameters of state of cold
fermions and the first and second sound velocities. The parameters of pair
excitations show a remarkable agreement with the Monte Carlo data and with
experiment.Comment: 14 pages, 5 figure
Measurement of the D+ and Ds+ decays into K+K-K+
We present the first clear observation of the doubly Cabibbo suppressed decay
D+ --> K-K+K+ and the first observation of the singly Cabibbo suppressed decay
Ds+ --> K-K+K+. These signals have been obtained by analyzing the high
statistics sample of photoproduced charm particles of the FOCUS(E831)
experiment at Fermilab. We measure the following relative branching ratios:
Gamma(D+ --> K-K+K+)/Gamma(D+ --> K-pi+pi+) = (9.49 +/- 2.17(statistical) +/-
0.22(systematic))x10^-4 and Gamma(Ds+ --> K-K+K+)/Gamma(Ds+ --> K-K+pi+) =
(8.95 +/- 2.12(statistical) +2.24(syst.) -2.31(syst.))x10^-3.Comment: 10 pages, 8 figure
Study of Hadronic Five-Body Decays of Charmed Mesons
We study the decay of D+ and Ds+ mesons into charged five body final states,
and report the discovery of the decay mode D+ -> K+K-Pi+Pi+Pi-, as well as
measurements of the decay modes D+ -> K-Pi+Pi+Pi+Pi-, Ds+ -> K+K-Pi+Pi+Pi-, Ds+
-> PhiPi+Pi+Pi- and D+/Ds+ -> Pi+Pi+Pi+Pi-Pi-. An analysis of the resonant
substructure is also included, with evidence suggesting that both decays
proceed primarily through an a1 vector resonance.Comment: 11 pages, 3 figure
New Measurements of the D+ to K* mu nu Form Factor Ratios
Using a large sample of D+ to K- pi+ mu+ nu decays collected by the FOCUS
photoproduction experiment at Fermilab, we present new measurements of two
semileptonic form factor ratios: rv and r2. We find rv = 1.504 \pm 0.057 \pm
0.039 and r2 = 0.875 \pm 0.049 \pm 0.064. Our form factor results include the
effects of the s-wave interference discussed in a previous paper.Comment: 12 pages, 5 figure
Observation of a 1750 MeV/c^2 Enhancement in the Diffractive Photoproduction of K^+K^-
Using the FOCUS spectrometer with photon beam energies between 20 and 160
\gev, we confirm the existence of a diffractively photoproduced enhancement in
at 1750 \mevcc with nearly 100 times the statistics of previous
experiments. Assuming this enhancement to be a single resonance with a
Breit-Wigner mass shape, we determine its mass to be
\mevcc and its width to be \mevcc. We find no
corresponding enhancement at 1750 \mevcc in , and again neglecting any
possible interference effects we place limits on the ratio . Our results are consistent with previous
photoproduction experiments, but, because of the much greater statistics,
challenge the common interpretation of this enhancement as the
seen in annihilation experiments.Comment: 10 pages, 5 figure
Investigating the effect of GaCl3 incorporation into the usual CdCl2 treatment on CdTe-based solar cell device structures
The incorporation of GaCl3 into the usual CdCl2 post-deposition treatment solution of CdTe-based solar cells has been investigated. Both CdS and CdTe layers used in this work were prepared by electroplating technique and they are n-type in electrical conduction as observed from photoelectrochemical cell measurement technique. Before applying the chemical treatments to the device structures, the effect of GaCl3 incorporation into the usual CdCl2 treatment was first studied on the structural and optical properties of CdTe thin films. The results of the optical properties show that the bandgap of CdTe thin films treated with a mixture of GaCl3 + CdCl2 is closer to that of bulk CdTe layers than the ones treated only with CdCl2 solution. The structural properties also showed that CdTe thin films treated with GaCl3 + CdCl2 is more crystalline than CdTe thin films treated only with CdCl2 solution. The addition of GaCl3 into the CdCl2 solution have been seen to drastically enhance the solar-to-electric conversion efficiency of CdS/CdTe based solar cells. One of the effects of Ga incorporation into the usual CdCl2 treatment was seen in the series resistance reduction which ultimately leads to enhancement in the observed short-circuit current density, fill factor and overall solar cell efficiency. For the glass/FTO/n-CdS/n-CdTe device structures, the cell efficiencies were observed in the range 1.9–2.1% after being treated with CdCl2 solution only. When treated with CdCl2 + GaCl3, the efficiency increased to 6.1–6.4%. Subsequent study on multi-junction graded bandgap solar cells using the GaCl3 + CdCl2 chemical solution for the surface treatment of glass/FTO/n-ZnS/n-CdS/n-CdTe device structures results in solar cell efficiency >10%
Charm System Tests of CPT and Lorentz Invariance with FOCUS
We have performed a search for CPT violation in neutral charm meson
oscillations. While flavor mixing in the charm sector is predicted to be small
by the Standard Model, it is still possible to investigate CPT violation
through a study of the proper time dependence of a CPT asymmetry in right-sign
decay rates for and \d0b\to K^+\pi^-. This asymmetry is
related to the CPT violating complex parameter and the mixing parameters
and : . Our 95% confidence
level limit is . Within the
framework of the Standard Model Extension incorporating general CPT violation,
we also find 95% confidence level limits for the expressions involving
coefficients of Lorentz violation of GeV, GeV, and GeV,
where is the factor which incorporates mixing parameters ,
and the doubly Cabibbo suppressed to Cabibbo favored relative strong phase
.Comment: 12 pages 5 figure
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