38,341 research outputs found

    Summary of Working Group I: Hadron Structure

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    A summary is given on the main aspects which were discussed by the working group. They include new results on the deep inelastic scattering structure functions F2,xF3,FLF_2, xF_3, F_L and F2ccˉF_2^{c\bar{c}} and their parametrizations, the measurement of the gluon density, recent theoretical work on the small xx behavior of structure functions, theoretical and experimental results on αs\alpha_s, the direct photon cross section, and a discussion of the event rates in the high pTp_T range at Tevatron and the high Q2Q^2 range at HERA, as well as possible interpretations.Comment: 22 pages latex, including 8 figures (ps,eps), to appear in the Proceedings of the International Conference on Deep Inelastic Scattering, Chicago, April 1997, AI

    Non-axisymmetric oscillations of rapidly rotating relativistic stars by conformal flatness approximation

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    We present a new numerical code to compute non-axisymmetric eigenmodes of rapidly rotating relativistic stars by adopting spatially conformally flat approximation of general relativity. The approximation suppresses the radiative degree of freedom of relativistic gravity and the field equations are cast into a set of elliptic equations. The code is tested against the low-order f- and p-modes of slowly rotating stars for which a good agreement is observed in frequencies computed by our new code and those computed by the full theory. Entire sequences of the low order counter-rotating f-modes are computed, which are susceptible to an instability driven by gravitational radiation.Comment: 3 figures. To appear in Phys.Rev.

    Rossby-Haurwitz waves of a slowly and differentially rotating fluid shell

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    Recent studies have raised doubts about the occurrence of r modes in Newtonian stars with a large degree of differential rotation. To assess the validity of this conjecture we have solved the eigenvalue problem for Rossby-Haurwitz waves (the analogues of r waves on a thin-shell) in the presence of differential rotation. The results obtained indicate that the eigenvalue problem is never singular and that, at least for the case of a thin-shell, the analogues of r modes can be found for arbitrarily large degrees of differential rotation. This work clarifies the puzzling results obtained in calculations of differentially rotating axi-symmetric Newtonian stars.Comment: 8pages, 3figures. Submitted to CQ

    Oscillations of vertically integrated relativistic tori -II. Axisymmetric modes in a Kerr spacetime

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    This is the second of a series of papers investigating the oscillation properties of relativistic, non-selfgravitating tori orbiting around black holes. Extending the work done in a Schwarzschild background, we here consider the axisymmetric oscillations of vertically integrated tori in a Kerr spacetime. The tori are modeled with a number of different non-Keplerian distributions of specific angular momentum and we discuss how the oscillation properties depend on these and on the rotation of the central black hole. We first consider a local analysis to highlight the relations between acoustic and epicyclic oscillations in a Kerr spacetime and subsequently perform a global eigenmode analysis to compute the axisymmetric p modes. In analogy with what found in a Schwarzschild background, these modes behave as sound waves that are modified by rotation and are globally trapped in the torus. For constant distributions of specific angular momentum, the eigenfrequencies appear in a sequence 2:3:4:... which is essentially independent of the size of the disc and of the black hole rotation. For non-constant distributions of angular momentum, on the other hand, the sequence depends on the properties of the disc and on the spin of the black hole, becoming harmonic for sufficiently large tori. We also comment on how p modes could explain the high frequency quasi-periodic oscillations observed in low-mass X-ray binaries with a black hole candidate and the properties of an equivalent model in Newtonian physics.Comment: 13 pages, MNRAS, in pres
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