Z_2 Monopoles, Vortices and the Universality of the SU(2) Deconfinement Transition

We investigate the effect of $Z_2$ magnetic monopoles and vortices on the finite temperature deconfinement phase transition in the fundamental - adjoint SU(2) lattice gauge theory. In the limit of complete suppression of the $Z_2$ monopoles, the mixed action for the SU(2) theory in its Villain form is shown to be self-dual under the exchange of the fundamental and adjoint couplings. By further suppressing the $Z_2$ vortices we show that the extended model reduces to the Wilson action with a modified coupling. The universality of the SU(2) deconfinement phase transition with the Ising model is therefore expected to remain intact in the entire plane of the fundamental-adjoint couplings in the continuum limit. The self-duality arguments related to the suppression of $Z_2$ monopoles are also applicable to the Villain form of mixed action for the SU(N) theory with $Z_{N}$ magnetic monopoles.Comment: 12 pages, Latex, To appear in Phys. Lett.

The information paradox: conflicts and resolutions

Many relativists have been long convinced that black hole evaporation leads to information loss or remnants. String theorists have however not been too worried about the issue, largely due to a belief that the Hawking argument for information loss is flawed in its details. A recently derived inequality shows that the Hawking argument for black holes with horizon can in fact be made rigorous. What happens instead is that in string theory black hole microstates have no horizons. Thus the evolution of radiation quanta with E ~ kT is modified by order unity at the horizon, and we resolve the information paradox. We discuss how it is still possible for E >> kT objects to see an approximate black hole like geometry. We also note some possible implications of this physics for the early Universe.Comment: 26 pages, 8 figures, Latex; (Expanded version of) proceedings for Lepton-Photon 201

More On The SU(2) Deconfinement Transition In The Mixed Action

We examine certain issues related to the universality of the SU(2) lattice gauge theory at non-zero temperatures. Using Monte Carlo simulations and strong coupling expansions, we study the behavior of the deconfinement transition in an extended coupling plane (beta, beta_A) around the tricritical point where the deconfinement transition changes from second to first order. Our numerical results on N_tau =2,4,6,8 lattices show that the tricritical point first moves down towards the Wilson axis and and then moves slowly upwards, if at all, as the lattice spacing is reduced. Lattices with very large N_tau seem to be therefore necessary for the mixed action to exhibit the critical exponents of the three dimensional Ising model for positive values of the adjoint coupling.Comment: LaTeX, 35 Pages including 8 Postscript Figures, Final version to be published in Phys. Rev. D, Title changed in the journal, Additional results on larger lattices presented which change somewhat our earlier conclusions. Added a reference and 4 figure

Laser discrimination by stimulated emission of a phosphor

A method for discriminating sources of UV, near infrared, and far infrared laser radiation was discovered. This technology is based on the use of a single magnesium sulfide phosphor doubly doped with rare earth ions, which is thermally/optically stimulated to generate colors correlatable to the incident laser radiation. The phosphor, after initial charging by visible light, exhibits green stimulated luminescence when exposed to a near infrared source (Nd: YAG laser). On exposure to far infrared sources (CO2 laser) the phosphor emission changes to orange color. A UV laser produces both an orange red as well as green color. A device using this phosphor is useful for detecting the laser and for discriminating between the near infrared, far infrared, and UV lasers. The technology is also capable of infrared laser diode beam profiling since the radiation source leaves an imprint on the phosphor that can be photographed. Continued development of the technology offers potential for discrimination between even smaller bandwidths within the infrared spectrum, a possible aid to communication or wavemixing devices that need to rapidly identify and process optical signals

Chandra LETGS spectroscopy of the Quasar MR2251-178 and its warm absorber

We present an analysis of our Chandra Low Energy Transmission Grating Spectrometer (LETGS) observation of the quasar MR2251-178. The warm absorber of MR2251-178 is well described by a hydrogen column density, N_H~2x10^21 cm^-2, and an ionization parameter log(xi)~0.6. We find in the spectrum weak evidence for narrow absorption lines from Carbon and Nitrogen which indicate that the ionized material is in outflow. We note changes (in time) of the absorption structure in the band (0.6-1) keV (around the UTAs plus the OVII and OVIII K-edges) at different periods of the observation. We measure a (0.1-2) keV flux of 2.58x10^-11 ergs cm^-2 s^-1. This flux implies that the nuclear source of MR2251-178 is in a relatively low state. No significant variability is seen in the light curve. We do not find evidence for an extra cold material in the line of sight, and set an upper limit of N_H~1.2x10^20 cm^-2. The X-ray spectrum does not appear to show evidence for dusty material, though an upper limit in the neutral carbon and oxygen column densities can only be set to N_CI~2x10^19 cm^-2 and N_OI~9x10^19 cm^-2, respectively.Comment: 42 pages, 12 figures, Accepted in Apj. Typo in abstract (ver2): "We do not find evidence for an extra...

Microzonation Studies for Delhi, Jabalpur & Dehradun as Impacted by Bhuj Earthquake

History of earthquakes in our country demonstrate vulnerability to seismic hazards. The recent past, devastating earthquakes in urban areas in India causing heavy economical losses in terms of loss of life, property, disruption of services and damage to environment have been of great concern; the experiences have prompted to carry out in-depth studies and come out with solutions and policies which will go a long way in minimizing the damages caused by seismic ground motions. In this context, microzonation of urban areas have assumed new dimensions. Delhi, the capital city of India has a long seismic history and is being affected by local as well as by the Himalayan earthquakes. The Jabalpur urban agglomeration lies in the field of recurrent seismicity ascribed to the reverse activation of Son-Narmada South Fault. Dehradun, the capital city of Uttaranchal is located in the foot hills of Himalayas and is sitting on a tectonically isolated block confined between main boundary thrust & Himalayan Frontal Thrust. Macroseismic surveys of the earthquake effects have unraveled site-dependent ground amplifications increasing the vulnerability of the built environment to seismic hazards. Hence, a need is felt to carry out prognostic damage scenario of existing building stocks in urban area, review the existing codal provision of buildings so that appropriate disaster mitigation measures can be evolved. Keeping this in view, CBRI, Roorkee (India) has carried out studies to generate inputs on vulnerability of engineered and non-engineered structures and anthropic parameters of population living in dwelling susceptible to damage and other exposure factors for fourth level seismic risk microzonation with engineering seismological perspective. The paper briefly describes the microzonation studies initiated in India for Delhi, the capital city of India, Jabalpur & Dehradun, the capital of newly formed Indian state, Uttaranchal. The paper presents two approaches namely Demand Capacity Ratio (DCR) approach & Rapid Screening Procedure(RSP) for assessment of seismic vulnerability of existing building stocks

Comments on black holes I: The possibility of complementarity

We comment on a recent paper of Almheiri, Marolf, Polchinski and Sully who argue against black hole complementarity based on the claim that an infalling observer 'burns' as he approaches the horizon. We show that in fact measurements made by an infalling observer outside the horizon are statistically identical for the cases of vacuum at the horizon and radiation emerging from a stretched horizon. This forces us to follow the dynamics all the way to the horizon, where we need to know the details of Planck scale physics. We note that in string theory the fuzzball structure of microstates does not give any place to 'continue through' this Planck regime. AMPS argue that interactions near the horizon preclude traditional complementarity. But the conjecture of 'fuzzball complementarity' works in the opposite way: the infalling quantum is absorbed by the fuzzball surface, and it is the resulting dynamics that is conjectured to admit a complementary description.Comment: 34 pages, 6 figures, v3: clarifications & references adde

A Study of the Bulk Phase Transitions of the SU(2) Lattice Gauge Theory with Mixed Action

Using the finite size scaling theory, we re-examine the nature of the bulk phase transition in the fundamental-adjoint coupling plane of the SU(2) lattice gauge theory at $\beta_A = 1.25$ where previous finite size scaling investigations of the deconfinement phase transition showed it to be of first order for temporal lattices with four sites. Our simulations on $N^4$ lattices with N=6, 8, 10, 12 and 16 show an absence of a first order bulk phase transition. We find the discontinuity in the average plaquette to decrease approximately linearly with $N$. Correspondingly, the plaquette susceptibility grows a lot slower with the 4-volume of the lattice than expected from a first order bulk phase transition.Comment: LaTeX, 17 Pages; 7 Postscript Figures appende