1,721,188 research outputs found
Remo Ruffini Festschrift
No full textA conference celebrating Remo Ruffini's 80th birthday was held in Nice, France, from 16 to 18 May 2022, with the participation of over 90 scientists. Among the contributions presented orally there were those by Rashid Sunyaev, Peter Predehl, Demetrios Christodoulou, Thibault Damour, Nathalie Deruelle, Roy Kerr, Tsvi Piran, Claus Laemmerzahl, Asghar Qadir, Chen Pisin, and Marco Tavani, in the presence of Agnès Rampal, the representative of the Mayor of Nice. An extraordinary moment of the meeting in Nice was the delivery of the Marcel Grossmann Award to Rashid Sunyaev and Peter Predehl for the Spectr–Roentgen–Gamma (SRG) mission. This volume contains 10 papers by some of the meeting participants and collaborators of Remo Ruffini
Quantum Liouville theory with heavy charges
No full textThe Marcel Grossmann Meetings are three-yearly forums that meet to discuss recent advances in gravitation, general relativity and relativistic field theories, emphasizing their mathematical foundations, physical predictions and experimental tests. These meetings aim to facilitate the exchange of ideas among scientists, to deepen our understanding of space–time structures, and to review the status of ongoing experiments and observations testing Einstein's theory of gravitation either from ground or space-based experiments. Since the first meeting in 1975 in Trieste, Italy, which was established by Remo Ruffini and Abdus Salam, the range of topics presented at these meetings has gradually widened to accommodate issues of major scientific interest, and attendance has grown to attract more than 900 participants from over 80 countries
Supersymmetry and Inflation
No full textA variant of hybrid inflation which is applicable in a wide class of supersymmetric grand unified models and reproduces the observed temperature perturbations of cosmic background radiation with natural values of the parameters is presented. The theory is consistent with the unification of the minimal supersymmetric standard model gauge couplings as measured at LEP. The termination of inflation is smooth and does not produce any topological defects. Numerical investigation of the cosmological evolution of the system shows that for almost all initial values of the fields we do get an adequate amount of inflation. Finally, the "reheating" process following inflation and the production of the baryon asymmetry of the universe via a primordial lepton asymmetry are briefly discussed and some important implications for right handed neutrino Majorana masses are investigated
Casimir energy in non-covariant gauges
No full textThe zero-point energy of a conducting spherical shell is studied by imposing the axial gauge via path-integral methods, with boundary conditions on the electromagnetic potential and ghost fields. The coupled modes are then found to be the temporal and longitudinal modes for the Maxwell field. The resulting system can be decoupled by studying a fourth-order differential equation with boundary conditions on longitudinal modes and their second derivatives. Complete agreement is found with a previous path-integral analysis in the Lorenz gauge, and with Boyer’s value. This investigation leads to a better understanding of how gauge independence is achieved in quantum field theory on backgrounds with boundary
Lorenz gauge in quantum cosmology
No full textIn a path-integral approach to quantum cosmology, the Lorenz gauge-averaging term is studied for Euclidean Maxwell theory on a portion of flat four-space bounded by two concentric three-spheres, but with arbitrary values of the gauge parameter. The resulting set of eigenvalue equations for normal and longitudinal modes of the electromagnetic potential cannot be decoupled, and is here studied with a Green-function method. This means that an equivalent equation for longitudinal modes is obtained which has integro-differential nature, after inverting a differential operator in the original coupled system. A complete calculational scheme is therefore obtained for the one-loop semiclassical evaluation of the wave function of the universe in the presence of gauge fields. This might also lead to a better understanding of how gauge independence is actually achieved on manifolds with boundary, whose consideration cannot be avoided in a quantum theory ofthe universe
Recent progress on the tidal deformability of spinning compact objects
Full text linkWe give a short review on recent progress in the theory of tidal deformability of a slowly spinning compact object. A rotating object immersed in a quadrupolar, electric tidal field can acquire some induced mass, spin, quadrupole, octupole and hexadecapole moments to second order in the spin. Angular momentum introduces couplings between electric and magnetic distortions and new classes of spin-induced, tidal Love numbers emerge. All tidal Love numbers of a Kerr black hole were proved to be exactly zero to first order in the spin and also to second order in the spin, at least in the axisymmetric case. The tidal Love numbers of a neutron star depend strongly on the equation of state. Spin-tidal couplings deteriorate some approximate universal relations that exist for neutron stars in the static case. For a binary system close to the merger, various components of the tidal field become relevant. Preliminary results suggest that spin-tidal couplings can introduce important corrections to the gravitational waveforms of spinning neutron-star binaries approaching the merger
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