51,422 research outputs found
On the Unique Solution of Planet and Star Parameters from an Extrasolar Planet Transit Light Curve
There is a unique solution of the planet and star parameters from a planet
transit light curve with two or more transits if the planet has a circular
orbit and the light curve is observed in a band pass where limb darkening is
negligible. The existence of this unique solution is very useful for current
planet transit surveys for several reasons. First, there is an analytic
solution that allows a quick parameter estimate, in particular of Rp. Second,
the stellar density can be uniquely derived from the transit light curve alone.
The stellar density can be used to immediately rule out a giant star (and hence
a much larger than planetary companion) and can also be used to put an upper
limit on the stellar and planet radius even considering slightly evolved stars.
Third, the presence of an additional fully blended star that contaminates an
eclipsing system to mimic a planet transit can be largely ruled out from the
transit light curve given a spectral type for the central star. Fourth, the
period can be estimated from a single-transit light curve and a measured
spectral type. All of these applications can be used to select the best planet
transit candidates for mass determination by radial velocity follow-up. To use
these applications in practice, the photometric precision and time sampling of
the light curve must be high (better than 0.005 mag precision and 5 minute time
sampling).Comment: 26 pages incl. 11 figs, submitted to Ap
Implications of the isotope effects on the magnetization, magnetic torque and susceptibility
We analyze the magnetization, magnetic torque and susceptibility data of
La2-xSrxCu(16,18)O4 and YBa2(63,65)CuO7-x near Tc in terms of the universal
3D-XY scaling relations. It is shown that the isotope effect on Tc mirrors that
on the anisotropy. Invoking the generic behavior of the anisotropy the doping
dependence of the isotope effects on the critical properties, including Tc,
correlation lengths and magnetic penetration depths are traced back to a change
of the mobile carrier concentration.Comment: 5 pages, 3 figure
A possible solution of the grain boundary problem for applications of high-Tc superconductors
It is shown that the critical current density of high-Tc wires can be greatly
enhanced by using a threefold approach, which consists of grain alignment,
doping, and optimization of the grain architecture. According to model
calculations, current densities of 4x10^6 A/cm2 can be achieved for an average
grain alignment of 10 degree at 77K. Based on this approach, a road to
competitive high-Tc cables is proposed.Comment: 3 pages, 5 figure
The Heavy Quark Form Factors at Two Loops
We compute the two-loop QCD corrections to the heavy quark form factors in
case of the vector, axial-vector, scalar and pseudo-scalar currents up to
second order in the dimensional parameter . These terms are
required in the renormalization of the higher order corrections to these form
factors.Comment: 131 pages, 3 figure
Isotope effects in underdoped cuprate superconductors: a quantum phenomenon
We show that the unusual doping dependence of the isotope effects on
transition temperature and zero temperature in - plane penetration depth
naturally follows from the doping driven 3D-2D crossover, the 2D quantum
superconductor to insulator transition (QSI) in the underdoped limit and the
change of the relative doping concentration upon isotope substitution. Close to
the QSI transition both, the isotope coefficient of transition temperature and
penetration depth approach the coefficient of the relative dopant
concentration, and its divergence sets the scale. These predictions are fully
consistent with the experimental data and imply that close to the underdoped
limit the unusual isotope effect on transition temperature and penetration
depth uncovers critical phenomena associated with the quantum superconductor to
insulator transition in two dimensions.Comment: 6 pages, 3 figure
Heavy quark form factors at two loops in perturbative QCD
We present the results for heavy quark form factors at two-loop order in
perturbative QCD for different currents, namely vector, axial-vector, scalar
and pseudo-scalar currents, up to second order in the dimensional
regularization parameter. We outline the necessary computational details,
ultraviolet renormalization and corresponding universal infrared structure.Comment: 13 pages Latex, Proceedings of XLI International Conference of
Theoretical Physics "Matter to the Deepest", Podlesice, Poland, September
3-8, 2017 and RADCOR 2017, St.~Gilgen Austria, Sept 24-29, 201
Curvature representation of the gonihedric action
We analyse the curvature representation of the gonihedric action for
the cases when the dependence on the dihedral angle is arbitrary.Comment: 10 pages, LaTeX, 3 embedded figures with psfig, submitted to
Phys.Lett.
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