Nehomogen svemir s perfektnom tekućinom i elektromagnetskim poljem u Lyrinoj geometriji

A new class of cylindrically symmetric inhomogeneous cosmological models for perfect fluid distribution with electromagnetic field is obtained in the context of Lyra’s geometry. We obtained two types of solutions by considering the uniform as well as time dependent displacement field. The source of the magnetic field is due to an electric current produced along the z-axis. Only F12 is a non-vanishing component of the electromagnetic field tensor. To get the deterministic solution, it has been assumed that the expansion θ in the model is proportional to the shear σ. It has been found that the solutions are consistent with the recent observations of type Ia supernovae and that the displacement vector β(t) affects entropy. Physical and geometric aspects of the models are also discussed in the presence and absence of magnetic field.Našli smo novu klasu cilindrično-simetričnih nehomogenih kozmoloških modela za perfektnu raspodjelu tekućine i s elektromagnetskim poljem u okviru Lyrine geometrije. Postigli smo dvije vrste rješenja razmatrajući jednoliko i vremenski ovisno posmično polje. Magnetsko se polje proizvodi električnom strujom duž z-osi. Tako je prisutna jedino sastavnica F12 elektromagnetskog tenzora polja. Radi postizanja određenosti rješenja, u modelu se pretpostavlja razmjernost širenja θ s posmikom σ. Našli smo da su rješenja u skladu s nedavnim opažanjima Ia supernova te da posmični vektor β(t) utječe na entropiju. Raspravljaju se fizička i geometrijska svojstva modela uz i bez prisutnosti magnetskog polja

Nehomogen svemir s perfektnom tekućinom i elektromagnetskim poljem u Lyrinoj geometriji

A new class of cylindrically symmetric inhomogeneous cosmological models for perfect fluid distribution with electromagnetic field is obtained in the context of Lyra’s geometry. We obtained two types of solutions by considering the uniform as well as time dependent displacement field. The source of the magnetic field is due to an electric current produced along the z-axis. Only F12 is a non-vanishing component of the electromagnetic field tensor. To get the deterministic solution, it has been assumed that the expansion θ in the model is proportional to the shear σ. It has been found that the solutions are consistent with the recent observations of type Ia supernovae and that the displacement vector β(t) affects entropy. Physical and geometric aspects of the models are also discussed in the presence and absence of magnetic field.Našli smo novu klasu cilindrično-simetričnih nehomogenih kozmoloških modela za perfektnu raspodjelu tekućine i s elektromagnetskim poljem u okviru Lyrine geometrije. Postigli smo dvije vrste rješenja razmatrajući jednoliko i vremenski ovisno posmično polje. Magnetsko se polje proizvodi električnom strujom duž z-osi. Tako je prisutna jedino sastavnica F12 elektromagnetskog tenzora polja. Radi postizanja određenosti rješenja, u modelu se pretpostavlja razmjernost širenja θ s posmikom σ. Našli smo da su rješenja u skladu s nedavnim opažanjima Ia supernova te da posmični vektor β(t) utječe na entropiju. Raspravljaju se fizička i geometrijska svojstva modela uz i bez prisutnosti magnetskog polja

A Nearly Scale Invariant Spectrum of Gravitational Radiation from Global Phase Transitions

Using a large N sigma model approximation we explicitly calculate the power spectrum of gravitational waves arising from a global phase transition in the early universe and we confirm that it is scale invariant, implying an observation of such a spectrum may not be a unique feature of inflation. Moreover, the predicted amplitude can be over 3 orders of magnitude larger than the naive dimensional estimate, implying that even a transition that occurs after inflation may dominate in Cosmic Microwave Background polarization or other gravity wave signals.Comment: 4 pages, PRL published versio

A New Class of non-Hermitian Quantum Hamiltonians with PT Symmetry

In a remarkable development Bender and coworkers have shown that it is possible to formulate quantum mechanics consistently even if the Hamiltonian and other observables are not Hermitian. Their formulation, dubbed PT quantum mechanics, replaces hermiticity by another set of requirements, notably that the Hamiltonian should be invariant under the discrete symmetry PT, where P denotes parity and T denotes time reversal. All prior work has focused on the case that time reversal is even (T^2 = 1). We generalize the formalism to the case of odd time reversal (T^2 = -1). We discover an analogue of Kramer's theorem for PT quantum mechanics, present a prototypical example of a PT quantum system with odd time reversal, and discuss potential applications of the formalism. Odd time reversal symmetry applies to fermionic systems including quarks and leptons and a plethora of models in nuclear, atomic and condensed matter physics. PT quantum mechanics makes it possible to enlarge the set of possible Hamiltonians that physicists could deploy to describe fundamental physics beyond the standard model or for the effective description of condensed matter phenomena.Comment: Replaced submitted version with accepted version; to appear in Phys Rev

Beneficiation and Processing of some Important Raw Materials, for Iron and Steel Production

India is committed to a policy of industrialisation and, along with others, the mineral industries are also expanding. The iron and still industry in the country can be considered to be fairly well est- ablished and with the expansion of the existing plants and the erection of three new plants, the steel ingot production is expected to go up to six million tons by the end of the Second plan period. Four ferro-manganese plants in the country viz. i) The Tata Iron and Steel Company's plant at joda ii) Jeypore Mining Syndicate's at Raygada (Orissa}, iii) Ferro Alloys Corporation at Garividi (Andhra) and (iv)Electro Metallurgical works Private Ltd., at Dandeli (Bombay) have gone into production and five more plants are expected to be established shortly to increase the production to 1,60,000 tons, of which 1 lakh will be for export and the remainder for internal consumption

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

Annihilation Diagrams in Two-Body Nonleptonic Decays of Charmed Mesons

In the pole-dominance model for the two-body nonleptonic decays of charmed mesons $D \rightarrow PV$ and $D \rightarrow VV$, it is shown that the contributions of the intermediate pseudoscalar and the axial-vector meson poles cancel each other in the annihilation diagrams in the chiral limit. In the same limit, the annihilation diagrams for the $D \rightarrow PP$ decays vanish independently.Comment: 9 pages (+ 3 figures available upon request), UR-1316, ER-40685-766, IC/93/21

Precise time and frequency intercomparison between NPL, India and PTB, Federal Republic of Germany via satellite symphonie-1

A time and frequency intercomparison experiment conducted using Earth stations in New Delhi, India and Raisting, FRG is described. The NPL clock was placed at New Delhi Earth Station and the Raisting Clock was calibrated with PTB/Primary standard via LORAN-C and travelling clocks. The random uncertainity of time comparisons, represented by two sample Allan Variance sigma (30 seconds), was less than 10 nanoseconds. The relative frequency difference between the NPL and Raisting Clocks, SNPL, RAIS, as measured over the 44 days period was found to be -15.7 x 10 to the -13th power. The relative frequency difference between PTB Primary Standard and Raisting Clock, SPTB, RAIS, during this period, was measured to be -22.8 x 10 to the -13th power. The relative frequency difference between NPL clock and PTB Primary Standard, SNPL, PTB, thus, is +7.1 x 10 to the -13th power. The clock rate (UTC, India) of +7.1 + or - 0.5 x 10 to the -13th power, agrees well with that obtained via VLF phase measurements over one year period and with USNO travelling clock time comparisons made in September, 1980