Classifying Ellipsis in Dialogue: A Machine Learning Approach

Articl

Field-dependent diamagnetic transition in magnetic superconductor Sm1.85Ce0.15CuO4−ySm_{1.85} Ce_{0.15} Cu O_{4-y}

The magnetic penetration depth of single crystal $\rm{Sm_{1.85}Ce_{0.15}CuO_{4-y}}$ was measured down to 0.4 K in dc fields up to 7 kOe. For insulating $\rm{Sm_2CuO_4}$, Sm$^{3+}$ spins order at the N\'{e}el temperature, $T_N = 6$ K, independent of the applied field. Superconducting $\rm{Sm_{1.85}Ce_{0.15}CuO_{4-y}}$ ($T_c \approx 23$ K) shows a sharp increase in diamagnetic screening below $T^{\ast}(H)$ which varied from 4.0 K ($H = 0$) to 0.5 K ($H =$ 7 kOe) for a field along the c-axis. If the field was aligned parallel to the conducting planes, $T^{\ast}$ remained unchanged. The unusual field dependence of $T^{\ast}$ indicates a spin freezing transition that dramatically increases the superfluid density.Comment: 4 pages, RevTex

Electron cyclotron maser emission mode coupling to the z-mode on a longitudinal density gradient in the context of solar type III bursts

Copyright 2012 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. This article appeared in Physics of Plasmas 19, 110702 (2012) and may be found at .supplemental material at http://astro.qmul.ac.uk/~tsiklauri/sp.htmlsupplemental material at http://astro.qmul.ac.uk/~tsiklauri/sp.htm

Exclusive production of ω\omega meson in proton-proton collisions at high energies

First we calculate cross section for the $\gamma p \to \omega p$ reaction from the threshold to very large energies. At low energies the pion exchange is the dominant mechanism. At large energies the experimental cross section can be well described within the $k_{t}$-factorization approach by adjusting light-quark constituent mass. Next we calculate differential distributions for the $p p \to p p \omega$ reaction at RHIC, Tevatron and LHC energies for the first time in the literature. We consider photon-pomeron (pomeron-photon), photon-pion (pion-photon) as well as diffractive hadronic bremsstrahlung mechanisms. The latter are included in the meson/reggeon exchange picture with parameters fixed from the known phenomenology. Interesting rapidity distributions are predicted. The hadronic bremsstrahlung contributions dominate at large (forward, backward) rapidities. At small energies the photon-pomeron contribution is negligible compared to the bremsstrahlung contributions. It could be, however, easily identified at large energies at midrapidities. Absorptions effects are included and discussed. Our predictions are ready for verification at RHIC and LHC.Comment: 21 pages, 14 figure

Light vector meson photoproduction at large t

We have studied in perturbative QCD all independent helicity amplitudes describing the photoproduction of light vector mesons at large $t$. We found a new hard production mechanism which is related to the possibility for a real photon to fluctuate into a massless $q\bar q$ pair in a chiral-odd spin configuration. Each helicity amplitude is given as a sum of a usual chiral-even contribution (when the helicities of quark and antiquark are antiparallel) and this additional chiral-odd part (where the helicities of quark and antiquark are parallel). The chiral-odd contribution is large, it leads to a dominance of the non spin-flip amplitude in a very broad region of intermediately high $|t|$. All amplitudes are expressed in terms of short distance asymptotics of the light-cone wave functions of vector meson (photon). We demonstrate that for each helicity amplitude there exists a soft non-factorizable contribution. We give arguments that for dominant non spin-flip helicity amplitude the relative contribution of the soft nonfactorizable interactions is numerically not large.Comment: 21 pages LATEX, 2 .eps figures, the colour factor of chiral-odd contributions is corrected, qualitative results remain unchange

Some combinatorial identities related to commuting varieties and Hilbert schemes

In this article we explore some of the combinatorial consequences of recent results relating the isospectral commuting variety and the Hilbert scheme of points in the plane

The Q2Q^2 dependence of the hard diffractive photoproduction of vector meson or photon and the range of pQCD validity

We consider two coupled problems. We study the dependence on photon virtuality $Q^2$ for the semihard quasi--elastic photoproduction of neutral vector mesons on a quark, gluon or real photon (at $s\gg p_{\bot}^2,\;Q^2; \; p_{\bot}^2\gg \mu^2 \approx (0.3$ GeV)$^2$). To this end we calculate the corresponding amplitudes (in an analytical form) in the lowest nontrivial approximation of perturbative QCD. It is shown that the amplitude for the production of light meson varies very rapidly with the photon virtuality near $Q^2=0$. We estimate the bound of the pQCD validity region for such processes. For the real incident photon the obtained bound for the $\rho$ meson production is very high. This bound decreases fast with the increase of $Q^2$, and we expect that the virtual photoproduction at HERA gives opportunity to test the pQCD results. The signature of this region is discussed. For the hard Compton effect the pQCD should work good at not too high $p_{\bot}$, and this effect seems measurable at HERA.Comment: ReVTeX, 36 pages, 5 Postscript figures, uses epsf.st

Gravitational Laser Back-Scattering

A possible way of producing gravitons in the laboratory is investigated. We evaluate the cross section electron + photon $\rightarrow$ electron + graviton in the framework of linearized gravitation, and analyse this reaction considering the photon coming either from a laser beam or from a Compton back-scattering process.Comment: 11 pages, 2 figures (available upon request), RevTeX, IFT-P.03/9

Discovery limits for Techni-Omega production in eγe\gamma Collisions

In a strongly-interacting electroweak sector with an isosinglet vector state, such as the techni-omega, $\omega_T$, the direct $\omega_T Z \gamma$ coupling implies that an $\omega_T$ can be produced by $Z \gamma$ fusion in $e \gamma$ collisions. This is a unique feature for high energy $e^+e^-$ or $e^-e^-$ colliders operating in an $e\gamma$ mode. We consider the processes $e^- \gamma \to e^- Z\gamma$ and $e^- \gamma \to e^- W^+ W^- Z$, both of which proceed via an intermediate $\omega_T$. We find that at a 1.5 TeV $e^+e^-$ linear collider operating in an $e\gamma$ mode with an integrated luminosity of 200 fb$^{-1}$, we can discover an $\omega_T$ for a broad range of masses and widths.Comment: To appear in the Proceedings of the 29th International Conference on High Energy Physics, Vancouver, July 1998, 5 pages, Latex, 7 postscript figure

The effect of electron beam pitch angle and density gradient on solar type III radio bursts

Copyright 2012 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. This article appeared in Physics of Plasmas 19, 112903 (2012) and may be found at .supplemental material at http://astro.qmul.ac.uk/~tsiklauri/sp.htmlsupplemental material at http://astro.qmul.ac.uk/~tsiklauri/sp.htm