559 research outputs found
The bulk kinetic power of the jets of GRS 1915+105
We calculate the minimum value of the power in kinetic bulk motion of the
galactic superluminal source GRS 1915+105. This value far exceeds the Eddington
luminosity for accretion onto a black hole of 10 solar masses. This large value
severely limits the possible carriers of the kinetic luminosity at the base of
the jet, and favours a jet production and acceleration controlled by a magnetic
field whose value, at the base of the jet, exceeds Gauss. The Blandford
and Znajek process can be responsible of the extraction of the rotational
energy of a Kerr black hole, if lasting long enough to provide the required
kinetic energy. This time, of the order of a day, implies that the process must
operate in a stationary, not impulsive, mode.Comment: 5 pages, Latex, accepted for publication in MNRAS as a lette
Monopole clusters, center vortices, and confinement in a Z(2) gauge-Higgs system
We propose to use the different kinds of vacua of the gauge theories coupled
to matter as a laboratory to test confinement ideas of pure Yang-Mills
theories. In particular, the very poor overlap of the Wilson loop with the
broken string states supports the 't Hooft and Mandelstam confinement criteria.
However in the Z(2) gauge-Higgs model we use as a guide we find that the
condensation of monopoles and center vortices is a necessary, but not
sufficient condition for confinement.Comment: 13 pages, 6 figures, minor changes, version to be published on Phys.
Rev.
Large center vortices and confinement in 3D Z(2) gauge theory
We study the role of large clusters of center vortices in producing
confinement in 3D Z(2) gauge theory. First, we modify each configuration of a
Monte Carlo-generated ensemble in the confined phase by removing the largest
cluster of center vortices, and show that the ensemble thus obtained does not
confine. Conversely, we show that removing all of the small clusters of center
vortices and leaving the largest one only, confinement is preserved, albeit
with a string tension significantly smaller than the original one. Remarkably,
also the string corrections due to the quantum fluctuations of the confining
flux tube are preserved by this transformation.Comment: 8 pages,5 figure
Integrable structures in LGTs near the deconfinement transition
In this contribution we review some recent results about the emergence of 2D
integrable systems in 3D Lattice Gauge Theories near the deconfinement
transition. We focus on some concrete examples involving the flux tube
thickness, the ratio of k-string tensions and Polyakov loops correlators in
various models.Comment: 8 pages, Poster contribution to the XXVII International Symposium on
Lattice Field Theory, July 26-31, 2009, Peking University, Beijing, Chin
String effects and the distribution of the glue in mesons at finite temperature
The distribution of the gluon action density in mesonic systems is
investigated at finite temperature. The simulations are performed in quenched
QCD for two temperatures below the deconfinment phase. Unlike the gluonic
profiles displayed at T=0, the action density iso-surfaces display a
prolate-spheroid like shape. The curved width profile of the flux-tube is found
to be consistent with the prediction of the free Bosonic string model at large
distances.Comment: 14 pages,10 figure
Site alteration effects from rocket exhaust impingment during a simulated Viking Mars landing. Part 1: Nozzle development and physical site alternation
A potential interference problem for the Viking '75 scientific investigation of the Martian surface resulting from retrorocket exhaust plume impingement of the surface was investigated experimentally and analytically. It was discovered that the conventional bell nozzle originally planned for the Viking Lander retrorockets would produce an unacceptably large amount of physical disturbance to the landing site. An experimental program was subsequently undertaken to find and/or develop a nozzle configuration which would significantly reduce the site alteration. A multiple nozzle configuration, consisting of 18 small bell nozzles, was shown to produce a level of disturbance that was considered by the Viking Lander Science Teams to be acceptable on the basis of results from full-scale tests on simulated Martian soils
Surgical management of “ab-extrinseco” main stem left coronary compression during pulmonary thromboendarterectomy
Extrinsic compression of the left main coronary artery (LMCA) is a common but often underestimated complication of severe pulmonary hypertension (PH) and resulting pulmonary artery (PA) dilatatio
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