Search results for " P.A.E.S."
showing 10 items of 309 documents
Accurate measurement of Poisson ratio in optical fibers based on forward-stimulated Brillouin scattering
2021
The interaction between light and sound in optical fibers is a phenomenon that researchers have been investigated for many decades. Among all the opto-acoustic effects that occurs in optical fibers, forward-stimulated Brillouin scattering (FSBS) has become of great interest as sensing mechanism due to the dependence of the excited acoustic resonances on both internal parameters [1] , [2] and surroundings [3] of the optical fiber. The vibrational modes behind FSBS are transverse acoustic resonances, in particular, the radial modes R 0m and the torsional-radial modes TR 2m . Most of the experiments reported based on FSBS exploit the properties of either the radial or the torsional-radial mode…
Probing new physics in B¯0→D(*)τ−ν¯τ using the longitudinal, transverse, and normal polarization components of the tau lepton
2017
We study the longitudinal, transverse, and normal polarization components of the tau lepton in the decays ${\overline{B}}^{0}\ensuremath{\rightarrow}{D}^{(*)}{\ensuremath{\tau}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\tau}}$ and discuss their role in searching for new physics (NP) beyond the standard model (SM). Starting with a model-independent effective Hamiltonian including non-SM four-Fermi operators, we obtain experimental constraints on different NP scenarios and investigate their effects on the polarization observables. In the SM the longitudinal and transverse polarizations of the tau lepton differ substantially from the corresponding zero lepton mass values of $…
Constraining New Physics with the Fermilab Measurement ofCPViolation inB→ψKs
1999
Recently, the CDF Collaboration has reported a measurement of the CP asymmetry in the $B\ensuremath{\rightarrow}\ensuremath{\psi}{K}_{s}$ decay: ${a}_{\ensuremath{\psi}{K}_{s}}{\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.79}_{\ensuremath{-}0.44}^{+0.41}$. We analyze the constraints that follow from this measurement on the size and the phase of contributions from new physics to $B\ensuremath{-}\overline{B}$ mixing. Defining the relative phase between the full ${M}_{12}$ amplitude and the standard model contribution to be $2{\ensuremath{\theta}}_{d}$, we find a new bound: $\mathrm{sin}2{\ensuremath{\theta}}_{d}\ensuremath{\gtrsim}\ensuremath{-}0.6(\ensuremath{-}0.87)$ at $1\ensuremat…
Dynamical mean-field theory and weakly non-linear analysis for the phase separation of active Brownian particles
2015
Recently, we have derived an effective Cahn-Hilliard equation for the phase separation dynamics of active Brownian particles by performing a weakly non-linear analysis of the effective hydrodynamic equations for density and polarization [Speck et al., Phys. Rev. Lett. 112, 218304 (2014)]. Here, we develop and explore this strategy in more detail and show explicitly how to get to such a large-scale, mean-field description starting from the microscopic dynamics. The effective free energy emerging from this approach has the form of a conventional Ginzburg-Landau function. On the coarsest scale, our results thus agree with the mapping of active phase separation onto that of passive fluids with …
On the Weyl transverse frames in type I spacetimes
2004
We apply a covariant and generic procedure to obtain explicit expressions of the transverse frames that a type I spacetime admits in terms of an arbitrary initial frame. We also present a simple and general algorithm to obtain the Weyl scalars $\Psi_2^T$, $\Psi_0^T$ and $\Psi_4^T$ associated with these transverse frames. In both cases it is only necessary to choose a particular root of a cubic expression.
SOLAR DYNAMICS OBSERVATORY DISCOVERS THIN HIGH TEMPERATURE STRANDS IN CORONAL ACTIVE REGIONS
2011
One scenario proposed to explain the million degrees solar corona is a finely-stranded corona where each strand is heated by a rapid pulse. However, such fine structure has neither been resolved through direct imaging observations nor conclusively shown through indirect observations of extended superhot plasma. Recently it has been shown that the observed difference in appearance of cool and warm coronal loops (~1 MK, ~2-3 MK, respectively) -- warm loops appearing "fuzzier" than cool loops -- can be explained by models of loops composed of subarcsecond strands, which are impulsively heated up to ~10 MK. That work predicts that images of hot coronal loops (>~6 MK) should again show fine s…
Analytical characterization of spectral anomalies in polychromatic apertured beams
2006
Abstract The power spectrum of polychromatic apertured spherical waves changes strongly in the vicinity of phase singularities. A spectral shift effect is observed and, in some cases, a spectral switch occurs together with a broadening of the power spectrum. Low-order moments of the power spectrum are evaluated in points of the focal volume with spectral anomalies. First-order analytical expressions are proposed for the evaluation of the relative spectral shift and the relative spectral broadening in the transverse focal plane and along the optical axis. The influence of the fractional bandwidth and the selected singularity order is considered.
First results of an Hα based search of classical Be stars in the Perseus Arm and beyond
2013
We investigate a region of the Galactic plane, between 120 <= l <= 140 and -1 <= b <= +4, and uncover a population of moderately reddened (E(B-V) \sim 1) classical Be stars within and beyond the Perseus and Outer Arms. 370 candidate emission line stars (13 <= r <= 16) selected from the INT Photometric H-alpha Survey of the Northern Galactic plane (IPHAS) have been followed up spectroscopically. A subset of these, 67 stars with properties consistent with those of classical Be stars, have been observed at sufficient spectral resolution (Delta_lambda \sim 2 - 4 Angstrom) at blue wavelengths to narrow down their spectral types. We determine these to a precision estimated to be…
Geometric phase in open systems.
2003
We calculate the geometric phase associated to the evolution of a system subjected to decoherence through a quantum-jump approach. The method is general and can be applied to many different physical systems. As examples, two main source of decoherence are considered: dephasing and spontaneous decay. We show that the geometric phase is completely insensitive to the former, i.e. it is independent of the number of jumps determined by the dephasing operator.
Coronal Magnetic Field Measurements Through Quasi-Transverse Propagation
2004
The QT-propagation of microwaves as a means to measure coronal magnetic fields and the inversion of circular polarization as an observational proof of the QT-propagation are discussed. The first part of the chapter briefly outlines the relevant geometry and mathematical relations. Then the state of the art in the coronal magnetography and some possibilities are demonstrated. We discuss use of the technique for coronal magnetography and give some estimates concerning the coronal magnetography with the forthcoming Frequency Agile Solar Radiotelescope.