Showing papers in "Modern Physics Letters A in 2001"
TL;DR: In this article, the authors analyzed the data of the Heidelberg-Moscow double beta decay experiment for the measuring period August 1990-May 2000 (54.9813 kg y or 723.44 molyears), published recently, are analyzed using the potential of the Bayesian method for low counting rates.
Abstract: The data of the Heidelberg–Moscow double beta decay experiment for the measuring period August 1990–May 2000 (54.9813 kg y or 723.44 molyears), published recently, are analyzed using the potential of the Bayesian method for low counting rates. First evidence for neutrinoless double beta decay is observed giving first evidence for lepton number violation. The evidence for this decay mode is 97% (2.2σ) with the Bayesian method, and 99.8% c.l. (3.1σ) with the method recommended by the Particle Data Group. The half-life of the process is found with the Bayesian method to be $T_{1/2}^{0
u} = (0.8\hbox{--}18.3)\times 10^{25}~{\rm y}$ (95% c.l.) with a best value of 1.5 × 1025y. The deduced value of the effective neutrino mass is, with the nuclear matrix elements from Ref. 1, = (0.11–0.56) eV (95% c.l.), with a best value of 0.39 eV. Uncertainties in the nuclear matrix elements may widen the range given for the effective neutrino mass by at most a factor 2. Our observation which at the same time means evide...
553 citations
TL;DR: In this article, the spectrum of density fluctuations in models of inflation based on a weakly self-coupled scalar matter field minimally coupled to gravity is calculated and the dependence of the predictions on modifications of the physics on length scales smaller than the Planck length is investigated.
Abstract: We calculate the spectrum of density fluctuations in models of inflation based on a weakly self-coupled scalar matter field minimally coupled to gravity, and specifically investigate the dependence of the predictions on modifications of the physics on length scales smaller than the Planck length. These modifications are encoded in terms of modified dispersion relations. Whereas for some classes of dispersion relations the predictions are unchanged compared to the usual ones which are based on a linear dispersion relation, for other classes important differences are obtained, involving tilted spectra, spectra with exponential factors and with oscillations. This is the case when the dispersion relation becomes complex. We conclude that the predictions of inflationary cosmology in these models are not robust against changes in the super-Planck-scale physics.
275 citations
TL;DR: In this paper, the authors apply the technique of complex paths to obtain Hawking radiation in different coordinate representations of the Schwarzschild space-time, and find that the radiation is recovered in these coordinates indicating the covariance of Hawking radiation.
Abstract: We apply the technique of complex paths to obtain Hawking radiation in different coordinate representations of the Schwarzschild space–time. The coordinate representations we consider do not possess a singularity at the horizon unlike the standard Schwarzschild coordinate. However, the event horizon manifests itself as a singularity in the expression for the semiclassical action. This singularity is regularized by using the method of complex paths and we find that Hawking radiation is recovered in these coordinates indicating the covariance of Hawking radiation. This also shows that there is no correspondence between the particles detected by the model detector and the particle spectrum obtained by the quantum field theoretic analysis — a result known in other contexts as well.
239 citations
TL;DR: In this article, the authors explore the conditions under which noncommutative quantum mechanics and the Landau problem are equivalent theories in the lowest Landau level and show that they are equivalent in the sense that if the potential in non-commutativity quantum mechanics is chosen as V=Ωℵ with ℵ defined in the text, then for the value $\tilde\theta=0.22\times 10^{-11}~{\rm cm}^2$ (which measures the noncommuteative effects of the space), the Land
Abstract: We explore the conditions under which noncommutative quantum mechanics and the Landau problem are equivalent theories. If the potential in noncommutative quantum mechanics is chosen as V=Ωℵ with ℵ defined in the text, then for the value $\tilde\theta=0.22\times 10^{-11}~{\rm cm}^2$ (which measures the noncommutative effects of the space), the Landau problem and noncommutative quantum mechanics are equivalent theories in the lowest Landau level. For other systems one can find different values for $\tilde\theta$ and, therefore, the possible bounds for $\tilde\theta$ should be searched in a physical independent scenario. This last fact could explain the different bounds for $\tilde\theta$ found in the literature.
157 citations
TL;DR: In this paper, the continuity equation relating the change in time of the position probability density to the gradient of the probability current density is generalized to PT-symmetric quantum mechanics and the normalization condition of eigenfunctions is modified in accordance with this new conservation law.
Abstract: The continuity, equation relating the change in time of the position probability density to the gradient of the probability current density is generalized to PT-symmetric quantum mechanics. The normalization condition of eigenfunctions is modified in accordance with this new conservation law and illustrated with some detailed examples.
155 citations
TL;DR: In this paper, the authors discuss some possible cosmological implications of noncommutative geometry and point out the possibility that non-commutativity may cause inflation induced fluctuations to become non-Gaussian and anisotropic, and may modify the short distance dispersion relations.
Abstract: We briefly discuss some possible cosmological implications of noncommutative geometry. While the noncommutativity we consider does not affect gravity, it can play an important role in the dynamics of other fields that are present in the early universe. We point out the possibility that noncommutativity may cause inflation induced fluctuations to become non-Gaussian and anisotropic, and may modify the short distance dispersion relations.
152 citations
TL;DR: The relationship between space-time-matter (STM) and brane theories was studied in this article, where it was shown that STM predicts local and nonlocal high energy corrections to general relativity in 4D, which are identical to those predicted by brane-world models.
Abstract: We study the relationship between space–time–matter (STM) and brane theories. These two theories look very different at first sight, and have different motivation for the introduction of a large extra dimension. However, we show that they are equivalent to each other. First we demonstrate that STM predicts local and nonlocal high-energy corrections to general relativity in 4D, which are identical to those predicted by brane-world models. Secondly, we point out that in brane models the usual matter in 4D is a consequence of the dependence of five-dimensional metrics on the extra coordinate. If the 5D bulk metric is independent of the extra dimension, then the brane is void of matter. Thus, in brane theory matter and geometry are unified, which is exactly the paradigm proposed in STM. Consequently, these two 5D theories share the same concepts and predict the same physics. This is important not only from a theoretical point of view, but also in practice. We propose to use a combination of both methods to alleviate the difficult task of finding solutions on the brane. We show an explicit example that illustrate the feasibility of our proposal.
118 citations
TL;DR: In this article, the method of the BRST constructions is adopted to the systems of second-class constraints by the construction of an auxiliary representations of the algebras of constraints in terms of Verma modules.
Abstract: The Lagrangian description of irreducible massless representations of the Poincare group with the corresponding Young tableaux having two rows along with some explicit examples including the notoph and Weyl tensor is given. For this purpose the method of the BRST constructions is adopted to the systems of second-class constraints by the construction of an auxiliary representations of the algebras of constraints in terms of Verma modules.
109 citations
TL;DR: In this article, the relation between Poisson sigma models on surfaces with boundary and deformation quantization is discussed, and a review aimed at the physics audience on the relation is presented.
Abstract: This is a review aimed at the physics audience on the relation between Poisson sigma models on surfaces with boundary and deformation quantization. These models are topological open string theories. In the classical Hamiltonian approach, we describe the reduced phase space and its structures (symplectic groupoid), explaining in particular the classical origin of the noncommutativity of the string endpoint coordinates. We also review the perturbative Lagrangian approach and its connection with Kontsevich's star product. Finally we comment on the relation between the two approaches.
100 citations
TL;DR: In this article, a wide class of solvable symmetric potentials was studied in order to identify conditions under which these potentials have regular solutions with complex energy, including conjugate energy pairs.
Abstract: We study a wide class of solvable symmetric potentials in order to identify conditions under which these potentials have regular solutions with complex energy. Besides confirming previous findings for two potentials, most of our results are new. We demonstrate that the occurrence of conjugate energy pairs is a natural phenomenon for these potentials and that the present method can readily be extended to further potential classes.
81 citations
TL;DR: In this article, the doublets of states in question continue to exist at complex conjugate energies in the strongly non-Hermitian regime, where the energy levels merge and disappear in many symmetric models.
Abstract: Apparently, the energy levels merge and disappear in many symmetric models. This interpretation is incorrect: In square-well model we demonstrate how the doublets of states in question continue to exist at complex conjugate energies in the strongly non-Hermitian regime.
TL;DR: In this paper, a general solution to the Vaidya-Tikekar model for a spherically symmetric superdense star was proposed, and it was shown that the equation of state (EOS) of a star with values of mass and radius within the experimental ranges for Her X-1 (a compact X-ray binary pulsar), agrees accurately with the EOS obtained by Horvath et al.
Abstract: Using a general solution to the Vaidya–Tikekar model for a spherically symmetric superdense star, we show that the equation of state (EOS) of a star with values of mass and radius within the experimental ranges for Her X-1 (a compact X-ray binary pulsar), agrees accurately with the EOS obtained by Horvath et al.,1 who considered a quark–diquark mixture in equilibrium. Nevertheless, we note that the boundary condition chosen for bosonic (diquark) component in Ref. 1 is not appropriate and the identification of Her X-1 as a quark–diquark star remains inconclusive.
TL;DR: In this paper, the authors studied the three-dimensional Schwarzschild-de Sitter (SdS3) black hole and established the relation between the mass, entropy and temperature for this black hole without any ambiguity.
Abstract: We study the three-dimensional Schwarzschild–de Sitter (SdS3) black hole which corresponds essentially to a conical defect. We compute the mass of the SdS3 black hole from the correct definition of the mass in asymptotically de Sitter space. Then we clarify the relation between the mass, entropy and temperature for this black hole without any ambiguity. We also establish the SdS3/CFT2-correspondence for the entropy by applying the Cardy formula to a CFT with a central charge c = 3l/2G3. Finally we discuss the entropy bounds for the SdS3 black hole.
TL;DR: In this article, an explicit construction of the covariant two-point function of the "massless" minimally coupled scalar field in de Sitter space is given, which is free of any infrared divergence.
Abstract: In a recent paper,1 it has been shown that negative norm states are indispensable for a fully covariant quantization of the minimally coupled scalar field in de Sitter space. Their presence, while leaving unchanged the physical content of the theory, offers an automatic and covariant renormalization of the vacuum energy divergence. This paper is a completion of our previous work. An explicit construction of the covariant two-point function of the "massless" minimally coupled scalar field in de Sitter space is given, which is free of any infrared divergence. The associated Schwinger commutator function and retarded Green's function are calculated in a fully gauge-invariant way, which also means coordinate independent.
TL;DR: In this article, the existence of a co-dual BRST symmetry for the usual BRST invariant Lagrangian density of an Abelian gauge theory in two dimensions of space-time where a U(1) gauge field is coupled to the Noether conserved current (constructed by the Dirac fields).
Abstract: We show the existence of a co(dual)-BRST symmetry for the usual BRST invariant Lagrangian density of an Abelian gauge theory in two dimensions of space–time where a U(1) gauge field is coupled to the Noether conserved current (constructed by the Dirac fields). Under this new symmetry, it is the gauge-fixing term that remains invariant and the symmetry transformations on the Dirac fields are analogous to the chiral transformations. This interacting theory is shown to provide a tractable field theoretical model for the Hodge theory. The Hodge dual operation is shown to correspond to a discrete symmetry in the theory and the extended BRST algebra for the generators of the underlying symmetries turns out to be reminiscent of the algebra obeyed by the de Rham cohomology operators of differential geometry.
TL;DR: In this article, the authors investigated the cosmological scenarios with a four-dimensional effective action which is connected with multidimensional, supergravity and string theories, and the solution for the scale factor is such that initially universe undergoes a decelerated expansion but in late times it enters into the accelerated expansion phase.
Abstract: We have investigated the cosmological scenarios with a four-dimensional effective action which is connected with multidimensional, supergravity and string theories. The solution for the scale factor is such that initially universe undergoes a decelerated expansion but in late times it enters into the accelerated expansion phase. In fact, it asymptotically becomes a de Sitter universe. The dilaton field in our model is a decreasing function of time and it becomes a constant in late time resulting the exit from the scalar–tensor theory to the standard Einstein's gravity. Also the dilaton field results in the existence of a positive cosmological constant in late times.
TL;DR: In this paper, the authors calculate the energy distribution of a charged regular black hole using the energy-momentum complexes of Einstein and Moller, and show that the energy of such a black hole can be computed using the Moller complex.
Abstract: We calculate the energy distribution of a charged regular black hole using the energy–momentum complexes of Einstein and Moller.
TL;DR: In this paper, the authors showed that the scalar cross-section σscalar for the elastic neutralino-nucleon scattering is in general several orders of magnitude below the sensitivity of current experiments.
Abstract: In SUGRA inspired supersymmetric models with universal boundary conditions for the soft masses, the scalar cross-section σscalar for the elastic neutralino–nucleon scattering is in general several orders of magnitude below the sensitivity of current experiments. For large tan β and low M1/2, m0 values, the theoretically predicted σscalar can approach the sensitivity of these experiments (≈ 10-6pb) being at the same time in agreement with recent cosmological data, which impose severe restrictions on the CDM relic density, and with accelerator experiments which put lower bounds on sparticle and Higgs boson masses. Further improvement of the sensitivity of DAMA and CDMS experiments will probe the large tan β region of the parameter space in the vicinity of the boundaries of the parameter space allowed by chargino and Higgs searches.
TL;DR: In this article, simultaneous measurements of β-decay rate with the aid of Ge(Li)-detectors performed at two laboratories 140 km apart (INR RAS, Troitsk, 60Co, and JINR, Dubna, 137Cs) from 15 March 2000 to 10 April 2000 are presented.
Abstract: Results of simultaneous measurements of β-decay rate with the aid of Ge(Li)-detectors performed at two laboratories 140 km apart (INR RAS, Troitsk, 60Co, and JINR, Dubna, 137Cs) from 15 March 2000 to 10 April 2000 are presented. Regular deviations of the count rate of γ-quanta following the β-decay of ~0.7% (INR RAS, 60Co) and ~0.2% (JINR, 137Cs) from the statistical average, are observed. The analysis of extremum deviations of γ--quanta count rate shows that the set of directions of tangents to the Earth's parallels of latitude at the extremum points of trajectories of motion in the space of each laboratory clearly forms three separate compact subsets of directions which agree, for two laboratories, to an accuracy of ±10°. This phenomenon is shown not to be explained on the basis of traditional notion. A possible explanation is suggested based on the hypothesis that there exists a new anisotropic interaction caused by the cosmological vectorial potential Ag, a new fundamental constant having, according to the experiments carried out, the coordinate of right ascension α ≈ 285° in the second equatorial system. This is in agreement with earlier experiments.
TL;DR: In this paper, the neutrinoless double beta decay has been shown to be a natural choice for leptogenesis and all models predicting Dirac masses are ruled out and only the degenerate and inverted hierarchical solutions are allowed for the three-generation Majorana neutrinos.
Abstract: Recently a positive indication of the neutrinoless double beta decay has been announced. We study the implications of this result taking into consideration earlier results on atmospheric neutrinos and solar neutrinos. We also include in our discussions the recent results from SNO and K2K. We point out that on the confidence level given for the double beta signal, the neutrino mass matrices are now highly constrained. All models predicting Dirac masses are ruled out and leptogenesis becomes a natural choice. Only the degenerate and the inverted hierarchical solutions are allowed for the three-generation Majorana neutrinos. In both cases we find that the radiative corrections destabilize the solutions and the LOW, VO and Just So solutions of the solar neutrinos are ruled out. For the four-generation case only the inverted hierarchical scenario is allowed.
TL;DR: In this paper, the projector valued field for the fuzzy sphere was derived, and non-commutative n-monopole configurations for the Chern class were shown to be integers.
Abstract: All fiber bundles with a given set of characteristic classes can be considered as particular projections of a more general bundle called a universal classifying space. This notion of projector valued field, a global definition of connections and gauge fields, may be useful in defining vector bundles for noncommutative base spaces. In this letter we derive the projector valued field for the fuzzy sphere, define noncommutative n-monopole configurations, and check that in the classical limit, using the machinery of noncommutative geometry, the corresponding topological charges (Chern class) are integers.
TL;DR: In this paper, a set of simulations of the macrolensing effects produced by large-scale cosmological violations of the energy conditions are presented and compared with the results of equal amounts of positive mass.
Abstract: We present a set of simulations of the macrolensing effects produced by large-scale cosmological violations of the energy conditions. These simulations show how the appearance of a background field of galaxies is affected when lensed by a region with an energy density equivalent to a negative mass ranging from 1012 to 1017|M⊙|. We compare with the macrolensing results of equal amounts of positive mass, and show that, contrary to the usual case where tangential arc-like structures are expected, there appear radial arcs — runaway filaments — and a central void. These results make the cosmological macrolensing produced by space–time domains where the weak energy conditions are violated, observationally distinguishable from standard regions. Whether large domains with negative energy density indeed exist in the universe can now be decided by future observations of deep fields.
TL;DR: Chromaticity effects introduced by the finite source size in microlensing events by presumed natural wormholes are studied in this paper, where it is shown that these effects provide a specific signature that allow to discriminate between ordinary and negative mass lenses through the spectral analysis of the micro-lensing event.
Abstract: Chromaticity effects introduced by the finite source size in microlensing events by presumed natural wormholes are studied It is shown that these effects provide a specific signature that allow to discriminate between ordinary and negative mass lenses through the spectral analysis of the microlensing events Both galactic and extragalactic situations are discussed
TL;DR: In this paper, the authors considered propagation of UHECR through the galaxy and showed that in the case of galactic origin of UECR, the anisotropy can reach considerable values.
Abstract: We considered propagation of Ultra High Energy Cosmic Rays (UHECR) through the galaxy. We investigated models with sources of UHECR distributed in the same way as Cold Dark Matter (CDM) in a self-consistent way, taking into account both extra-galactic and Galactic contributions. Using a very simple toy model of galactic magnetic field we showed that in the case of galactic origin of UHECRs the anisotropy can reach considerable values. In the case of extragalactic UHECRs origin, the anisotropy appears to be nonvanishing only for electron and photon components due to synchrotron losses, but it can hardly be reassured. The reason is an extremely low flux of UHE electrons and a too low level of γ-ray anisotropy.
TL;DR: In this paper, a low-energy effective action for massless open string modes is given by a combination of a Yang-Mills and a Chern-Simons like functional on the fuzzy world-volume.
Abstract: In this letter we review some recent work on the noncommutative geometry of branes on group manifolds. In particular, we show how fuzzy spaces arise in this context from an exact worldsheet description and we sketch the construction of a low-energy effective action for massless open string modes. The latter is given by a combination of a Yang–Mills and a Chern–Simons like functional on the fuzzy world-volume. It can be used to study condensation on various brane configurations in curved backgrounds.
TL;DR: In this article, the null geodesic motion in the brane world cosmology in the RS2 scenario and in the static universe in the bulk of the charged topological AdS black hole was studied.
Abstract: We study null bulk geodesic motion in the brane world cosmology in the RS2 scenario and in the static universe in the bulk of the charged topological AdS black hole We obtain equations describing the null bulk geodesic motion as observed in one lower dimension We find that the null geodesic motion in the bulk of the brane world cosmology in the RS2 scenario is observed to be under the additional influence of extra non-gravitational force by the observer on the three-brane, if the brane universe does not possess the Z2 symmetry As for the null geodesic motion in the static universe in the bulk of the charged AdS black hole, the extra force is realized even when the brane universe has the Z2 symmetry
TL;DR: In this article, the authors considered the brane universe in the bulk background of the charged topological AdS black holes and derived the generalized Cardy-Verlinde formula for the CFT with an R-charge.
Abstract: We consider the brane universe in the bulk background of the charged topological AdS black holes. The evolution of the brane universe is described by the Friedmann equations for a flat or an open FRW-universe containing radiation and stiff matter. We find that the temperature and entropy of the dual CFT are simply expressed in terms of the Hubble parameter and its time derivative, and the Friedmann equations coincide with thermodynamic formulas of the dual CFT at the moment when the brane crosses the black hole horizon. We obtain the generalized Cardy–Verlinde formula for the CFT with an R-charge, for any values of the curvature parameter k in the Friedmann equations.
TL;DR: In this paper, the role of perfect fluid at the initial state of expansion and asymptotical isotropization process of the initially anisotropic universe has been elucidated.
Abstract: Self-consistent system of nonlinear spinor field and Bianchi I (BI) gravitational one with time-dependent gravitational constant (G) and cosmological constant (Λ) has been studied. The initial and the asymptotic behaviors of the field functions and the metric one have been thoroughly investigated. Given Λ = Λ0/τ2, with , G has been estimated as a function of τ. The role of perfect fluid at the initial state of expansion and asymptotical isotropization process of the initially anisotropic universe has been elucidated.
TL;DR: In this paper, it was shown that Lorentz invariance implies that neutrinos in oscillation experiments are superpositions of massive particles with different energies and momenta.
Abstract: It is shown that Lorentz invariance implies that in general flavor neutrinos in oscillation experiments are superpositions of massive neutrinos with different energies and different momenta. It is also shown that for each process in which neutrinos are produced, there is either a Lorentz frame in which all massive neutrinos have the same energy or a Lorentz frame in which all massive neutrinos have the same momentum. In the case of neutrinos produced in two-body decay processes, there is a Lorentz frame in which all massive neutrinos have the same energy.
TL;DR: In this paper, a concise derivation of all uncertainty relations is given entirely within the context of phase-space quantization, without recourse to operator methods, to the direct use of Weyl's correspondence, or to marginal distributions of x and p.
Abstract: A concise derivation of all uncertainty relations is given entirely within the context of phase-space quantization, without recourse to operator methods, to the direct use of Weyl's correspondence, or to marginal distributions of x and p.