http://prints.iiap.res.in The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Search the Channel search http://prints.iiap.res.in/simple-search http://hdl.handle.net/2248/5693 Title: Formation and Observations of Shadow Bands During the Total Solar Eclipse of November 23, 2003 Near Maitri, Antarctic<br/><br/>Authors: Vats, Hari Om; Bagare, S. P; Bhandari, S. M<br/><br/>Abstract: The phenomenon of shadow bands takes place due to the scattering of sunlight by the irregularities in the local atmosphere. Observation of shadow bands were made just before and after the total solar eclipse (TSE) on November 23, 2003 near the Indian Antarctic station Maitri (long. 11°45″E and lat. 70°45″S). The formation and observations of shadow bands during this TSE are presented. The results of correlation analysis show that the correlation (1) falls to half at separation of ~ 35 cm in horizontal direction; and (2) also at ∼100ms time lag. The power spectrum of the shadow band fluctuations had a power law distribution (spectral index ∼ −2) which is different from earlier eclipse observations reported in the literature. However, it closely resembles theoretical predictions of the extended screen scintillation theory.<br/><br/>Description: Restricted Access http://hdl.handle.net/2248/5692 Title: Thermal Gravitational Waves from Primordial Black Holes<br/><br/>Authors: Sivaram, C; Arun, K<br/><br/>Abstract: Thermal gravitational waves can be generated in various sources such as, in the cores of stars, white dwarfs and neutron stars due to the fermion collisions in the dense degenerate Fermi gas [1-3]. Such high frequency thermal gravitational waves can also be produced during the collisions in a gamma ray burst [3] or during the final stages of the evaporation of primordial black holes [4]. Here we estimate the thermal gravitational waves from primordial black holes and estimate the integrated energy of the gravitational wave emission over the entire volume of the universe and over Hubble time. We also estimate the gravitational wave flux from gamma ray bursts and jets.<br/><br/>Description: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License(http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided thework is properly cited. http://hdl.handle.net/2248/5691 Title: Thermal Gravitational Waves<br/><br/>Authors: Sivaram, C; Arun, K<br/><br/>Abstract: There is a lot of current interest in sources of gravitational waves and active ongoing projects to detect such radiation, such as the LIGO project. These are long wavelength, low frequency gravitational waves. LISA would be sensitive to much longer wavelengths and lower fluxes. However compact stellar objects can generate high frequency (1016-1021 Hz) thermal gravitational radiation, which in the case of hot neutron stars can be high. Also white dwarfs and main sequence stars can generate such radiation from plasma-Coulomb collisions. Again gamma ray bursts and relativistic jets could also be sources of such radiation. Terminal stages of evaporating black holes could also generate high frequency gravitational radiation. A comparative study is made of the thermal gravitational wave emission from all of the above sources, and the background flux is estimated. The earliest phases of the universe close to the Planck scale would also leave remnant thermal gravitational waves. The integrated thermal gravitational flux as the universe expands is also estimated and compared with that from all the discrete sources discussed above. Possible schemes to detect such sources of high frequency thermal gravitational radiation are discussed and the physical principles involved are elaborated.<br/><br/>Description: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited. http://hdl.handle.net/2248/5690 Title: New Class of Dark Matter Objects and their Detection<br/><br/>Authors: Sivaram, C; Arun, K<br/><br/>Abstract: About one-fourth of the universe is thought to consist of dark matter. Yet there is no clear understanding about the nature of these particles. Commonly discussed dark matter candidates includes the so called WIMPs or weakly interacting massive particles with masses from about ~ 10GeV to 1TeV . These particles can gravitate to form a new class of objects in dark matter halos or around the galactic centre. We study in detail many properties of these objects (which are dark matter dominated and bounded by their self gravity), their formation and possibilities of their detection. Implications of the presence of such objects for star formation are also discussed. These objects could provide the possibility of forming primordial black holes distinct from the usual Hawking black holes and they could also provide a scenario for short duration gamma ray bursts, avoiding the baryon load problem.<br/><br/>Description: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.