http://dspace.rri.res.in:8080/jspui The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Search the Channel search http://dspace.rri.res.in:8080/jspui/simple-search http://hdl.handle.net/2289/5579 Title: The diffeomorphism constraint operator in loop quantum gravity<br/><br/>Authors: Varadarajan, Madhavan<br/><br/>Abstract: We construct the diffeomorphism constraint operator at finite triangulation from the basic holonomy- flux operators of Loop Quantum Gravity, and show that the action of its continuum limit provides an anomaly free representation of the Lie algebra of diffeomorphisms of the 3- manifold. Key features of our analysis include: (i) finite triangulation approximants to the curvature, F-ab(i) of the Ashtekar- Barbero connection which involve not only small loop holonomies but also small surface fluxes as well as an explicit dependence on the edge labels of the spin network being acted on (ii) the dependence of the small loop underlying the holonomy on both the direction and magnitude of the shift vector field (iii) continuum constraint operators which do not have finite action on the kinematic Hilbert space, thus implementing a key lesson from recent studies of parameterised field theory by the authors. Features (i) and (ii) provide the first hints in LQG of a conceptual similarity with the so called "mu-bar" scheme of Loop Quantum Cosmology. We expect our work to be of use in the construction of an anomaly free quantum dynamics for LQG.<br/><br/>Description: Open Access. http://hdl.handle.net/2289/5578 Title: Ultra-high energy cosmic rays and prompt TeV gamma rays from gamma ray bursts<br/><br/>Authors: Bhattacharjee, P.; Gupta, Nayantara<br/><br/>Abstract: Gamma ray bursts (GRBs) have been proposed as one possible class of sources of the ultrahigh energy cosmic ray (UHECR) events observed up to energies gtrsim 10^{20} eV. The synchrotron radiation of the highest energy protons accelerated within the GRB source should produce gamma rays up to TeV energies. Here we briefly discuss the implications on the energetics of the GRB from the point of view of the detectability of the prompt TeV gamma-rays of proton-synchrotron origin in GRBs in the up-coming ICECUBE muon detector in the south pole.<br/><br/>Description: Open Access. http://hdl.handle.net/2289/5577 Title: Spectral and polarization study of the double relics in Abell 3376 using the Giant Metrewave Radio Telescope and the Very Large Array<br/><br/>Authors: Kale, Ruta; Dwarakanath, K.S.; Bagchi, Joydeep; Paul, Surajit<br/><br/>Abstract: Double radio relics in galaxy clusters are rare phenomena that trace shocks in the outskirts of merging galaxy clusters. We have carried out a spectral and polarization study of the spectacular double relics in the galaxy cluster A3376 using the Giant Metrewave Radio Telescope at 150 and 325 MHz and the Very Large Array at 1400 MHz. The polarization study at 1400 MHz reveals a high degree of polarization (∼30 per cent) and aligned magnetic field vectors (not corrected for Faraday rotation) in the eastern relic. A highly polarized (>60 per cent) filamentary radio source of size ∼300 kpc near the eastern relic and north of the bent-jet radio galaxy is detected for the first time. The western relic is less polarized and does not show aligned magnetic field vectors. The distribution of spectral indices between 325 and 1400 MHz over the radio relics shows steepening from the outer to the inner edges of the relics. The spectral indices of the eastern and the western relics imply Mach numbers in the range 2.2–3.3. Remarkable features such as the inward filament extending from the eastern relic, the highly polarized filament, the complex polarization properties of the western relic and the separation of the brightest cluster galaxy from the intracluster medium by a distance >900 kpc are noticed in the cluster. A comparison with simulated cluster mergers is required to understand the complex properties of the double relics in the context of the merger in A3376. An upper limit [log(P1.4 GHz W Hz−1) < 23.0] on the strength of a Mpc size radio halo in A3376 is estimated.<br/><br/>Description: Restricted Access. http://hdl.handle.net/2289/5576 Title: Electronic Theses and Dissertation (ETD) achives at Raman Research Institute: An Overview<br/><br/>Authors: Benegal, Vrinda J.; Nagaraj, M.N.<br/><br/>Abstract: An arch motive of e-Theses is to make the research and scholarship conducted by graduate students readily accessible, and for the long-term archiving. The RRI library was established in 1979. The e-Theses archive is for full-text electronic copies of theses produced by research graduates from the Institute. It is an Open Access database aiming to make the material avail-able to the widest possible Academia. The RRI Library has a collection of theses in the Re-search areas of Astronomy & Astrophysics, Soft Condensed Matter, Theoretical Physics, Light and Matter Physics and these are the core subject branches students perform the research and produce the doctoral thesis. The Research and Educational Institutes, Universities, play a major role in the generation and dissemination of knowledge by facilitating research work and producing Ph.D. thesis. This product of Doctoral Dissertation becomes precious and a rare source of information. ETD database of the institute showcases its academic output on a single platform, which provide wider visibility and enhances the prestige of the Institute. It acts as a catalyst to the quality of research and helps in attracting new students and research scholars.<br/><br/>Description: Restricted Access Book chapter from Proceedings of ICKMODE-2013 Conference, held at SIT, Tumkur, Karnataka, India from 17th to 19th January 2013. Ed by Shekar Hp et al, 2013. page- 349.