Showing papers in "Modern Physics Letters A in 2003"
TL;DR: In this paper, the authors consider a model of interacting cosmological constant/quintessence, where dark matter and dark energy behave as two coexisting phases of a fluid, a thermally excited Bose component and a condensate, respectively.
Abstract: We consider a model of interacting cosmological constant/quintessence, where dark matter and dark energy behave as, respectively, two coexisting phases of a fluid, a thermally excited Bose component and a condensate, respectively. In a simple phenomenological model for the dark components interaction we find that their energy density evolution is strongly coupled during the universe evolution. This feature provides a possible way out for the coincidence problem affecting many quintessence models.
132 citations
TL;DR: In this article, the authors review a few topics in Planck-scale physics, with emphasis on possible manifestations in relatively low energy The selected topics include quantum fluctuations of spacetime, their cumulative effects, uncertainties in energy-momentum measurements, and low energy quantum-gravity phenomenology.
Abstract: We review a few topics in Planck-scale physics, with emphasis on possible manifestations in relatively low energy The selected topics include quantum fluctuations of spacetime, their cumulative effects, uncertainties in energy–momentum measurements, and low energy quantum-gravity phenomenology The focus is on quantum-gravity-induced uncertainties in some observable quantities We consider four possible ways to probe Planck-scale physics experimentally: (i) looking for energy-dependent spreads in the arrival time of photons of the same energy from GRBs; (ii) examining spacetime fluctuation-induced phase incoherence of light from extragalactic sources; (iii) detecting spacetime foam with laser-based interferometry techniques; (iv) understanding the threshold anomalies in high energy cosmic ray and gamma ray events Some other experiments are briefly discussed We show how some physics behind black holes, simple clocks, simple computers, and the holographic principle is related to Planck-scale physics We also discuss a formulation of the Dirac equation as a difference equation on a discrete Planck-scale spacetime lattice, and a possible interplay between Planck-scale and Hubble-scale physics encoded in the cosmological constant (dark energy)
119 citations
TL;DR: In this paper, a minimally coupled tachyon field rolling down to its ground state on the FRW brane is studied and a tachyonic potential which can implement power law inflation in the brane world cosmology is constructed.
Abstract: We study a minimally coupled tachyon field rolling down to its ground state on the FRW brane. We construct tachyonic potential which can implement power law inflation in the brane world cosmology. The potential turns out to be V0ϕ-1 on the brane and reduces to inverse square potential at late times when brane corrections to the Friedmann equation become negligible. We also do similar exercise with a normal scalar field and discover that the inverse square potential on the brane leads to power law inflation.
116 citations
TL;DR: In this paper, a method to extend to the bulk asymptotically flat static spherically symmetric brane-world metrics was proposed, in order to allow exact integration of the relevant equations along the (fifth) extra coordinate and make contact with the parametrized post-Newtonian formalism.
Abstract: We propose a method to extend to the bulk asymptotically flat static spherically symmetric brane-world metrics. We employ the multipole (1/r) expansion in order to allow the exact integration of the relevant equations along the (fifth) extra coordinate and make contact with the parametrized post-Newtonian formalism. We apply our method to three families of solutions previously appeared as candidates of black holes in the brane world and show that the shape of the horizon is very likely a flat "pancake" for astrophysical sources.
110 citations
TL;DR: In this paper, the authors investigate the Kepler problem using a symplectic structure consistent with the commutation rules of the noncommutative quantum mechanics and show that a noncommuttative parameter of the order of 10-58m2 gives observable corrections to the movement of the solar system.
Abstract: We investigate the Kepler problem using a symplectic structure consistent with the commutation rules of the noncommutative quantum mechanics. We show that a noncommutative parameter of the order of 10-58m2 gives observable corrections to the movement of the solar system. In this way, modifications in the physics of smaller scales imply modifications at large scales, something similar to the uv/ir mixing.
78 citations
TL;DR: In this article, the neutrino mass matrices with two texture zeros with respect to the mixing angle of atmospheric neutrinos were analyzed and compared with those of quark and charged-lepton masses.
Abstract: Out of the 15 3 × 3 neutrino mass matrices with two texture zeros, seven are compatible with the neutrino oscillation data. While two of them correspond to hierarchical neutrino masses and 1 to an inverted hierarchy, the remaining four correspond to degenerate masses. Moreover only the first three of the seven mass matrices are compatible with the maximal mixing angle of atmospheric neutrino and hence favored by data. We give compact expressions for mass matrices in terms of mass eigenvalues and study phenomenological implications for the seven cases. Similarity of the textures of the neutrino, charged-lepton mass matrices with those of quark mass matrices is also discussed.
77 citations
TL;DR: In this article, the relativistic quark model is used to estimate the two-photon decay rates of pseudoscalar, scalar and tensor states of charmonium and bottomonium.
Abstract: Two-photon decay rates of pseudoscalar, scalar and tensor states of charmonium and bottomonium are calculated in the framework of the relativistic quark model. Both relativistic effects and one-loop radiative corrections are taken into account. The obtained results are compared with other theoretical predictions and available experimental data.
69 citations
TL;DR: In this paper, the authors summarize recent findings that show how standard 4D Einstein gravity coupled to a conformal field theory can become massive in anti de Sitter space, due to the nonstandard "transparent" boundary condition given to the CFT fields and the fact that AdS space is not globally hyperbolic, because of the presence of a time-like boundary.
Abstract: In this review, we summarize recent findings that show how standard 4D Einstein gravity coupled to a conformal field theory can become massive in anti de Sitter space. Key ingredients in this phenomenon are nonstandard "transparent" boundary condition given to the CFT fields and the fact that AdS space is not globally hyperbolic, due to the presence of a time-like boundary.
68 citations
Journal Article•
64 citations
TL;DR: In this paper, the cosmological constant with respect to the velocity of light, Planck and Newton gravitational constants has been derived from distant supernovae observations, and it is shown that the current value remarkably agrees with the value indicated by distant supernova observations, i.e. of the order of the critical density.
Abstract: We advance the viewpoint that, only relevant modes of the vacuum fluctuations, namely, with wavelengths conditioned by the size, homogeneity, geometry and topology of the Universe, do contribute to the cosmological constant. A formula is derived which relates the cosmological constant with the size of the Universe and the three fundamental constants: the velocity of light, Planck and Newton gravitational constants. Then the current value of the cosmological constant remarkably agrees with the value indicated by distant supernovae observations, i.e. of the order of the critical density. Thus the cosmological constant had to be smaller than the matter density in the past and will be bigger in the future.
61 citations
TL;DR: In this article, the generalised Brans-Dicke theory was studied and exact solutions of a(t), ϕ(t) and ω(t ) for different epochs of the cosmic evolution were obtained.
Abstract: We have studied the generalised Brans–Dicke theory and obtained exact solutions of a(t), ϕ(t) and ω(t) for different epochs of the cosmic evolution. We discuss how inflation, deceleration, cosmic acceleration can result from this solution. The time variation of G(t) is also examined.
TL;DR: In this article, the effective Lagrangian of the Higgs penguin in the Standard Model and its minimal supersymmetric extension (MSSM) is reviewed and the B-meson decays into a lepton-antilepton pair.
Abstract: We review the effective Lagrangian of the Higgs penguin in the Standard Model and its minimal supersymmetric extension (MSSM). As a master application of the Higgs penguin, we discuss in some detail the B-meson decays into a lepton–antilepton pair. Furthermore, we explain how this can probe the Higgs sector of the MSSM provided that some of these decays are seen at Tevatron Run II and B-factories. Finally, we present a complete list of observables where the Higgs penguin could be strongly involved.
TL;DR: A short review of Schrodinger Hamiltonians for which the spectral problem has been related in the literature to the distribution of the prime numbers is presented in this paper, where a possible connection between prime numbers and centrifugal inversions in black holes is discussed.
Abstract: A short review of Schrodinger Hamiltonians for which the spectral problem has been related in the literature to the distribution of the prime numbers is presented here. We notice a possible connection between prime numbers and centrifugal inversions in black holes and suggest that this remarkable link could be directly studied within trapped Bose–Einstein condensates. In addition, when referring to the factorizing operators of Pitkanen and Castro and collaborators, we perform a mathematical extension allowing a more standard supersymmetric approach.
TL;DR: A brief summary of the currently available low dimensional fuzzy spaces and some of the simplest field theories permitted on these spaces is given in this paper, where a simple field theory for low-dimensional fuzzy spaces is presented.
Abstract: A brief summary is given of the currently available low dimensional fuzzy spaces and some of the simplest field theories permitted on these spaces.
TL;DR: The High Intensity Gamma-ray Source (HIγS) is a joint project between Triangle Universities Nuclear Laboratory (TUNL) and the Duke Free Electron Laser Laboratory (DFELL) as mentioned in this paper.
Abstract: The High Intensity Gamma-ray Source (HIγS) is a joint project between Triangle Universities Nuclear Laboratory (TUNL) and the Duke Free Electron Laser Laboratory (DFELL). This facility utilizes intra-cavity back-scattering of the FEL photons in order to produce a γ-flux enhancement of approximately 103 over the existing sources. At present, gamma-ray beams with energies ranging from 2 to 50 MeV are available with intensities of 105–107 γ/s, energy spreads of 1% or better (with lower intensities), and 100% linear polarization. An upgrade is presently underway which will allow for the production of γ rays up to an energy of about 225 MeV having intensities in excess of 108 γ/sec. The primary component of the upgrade is a 1.2 GeV booster-injector which will provide for efficient injection at any chosen operating energy of the storage ring from 300 MeV to 1.2 GeV. In addition, an upgrade of the present OK-4 FEL to a helical undulator system (OK-5) is underway. This new system has many advantages over the pres...
TL;DR: In this paper, the authors considered tachyonic inflation with inverse power-law potential and found the solution of the evolution equations in the slow-roll limit in FRW as well as in the brane cosmology.
Abstract: We consider issues related to tachyonic inflation with inverse-power-law potential. We find the solution of the evolution equations in the slow-roll limit in FRW as well as in the brane cosmology. Using the holographic entropy bound, we estimate the quantum-gravitational discreteness of tachyonic inflation perturbations.
TL;DR: In this article, the probability of detecting the topology of a multiconnected hyperbolic universe with a randomly placed observer at any point in the observable space was investigated.
Abstract: Cosmic microwave background data shows the observable universe to be nearly flat, but leaves open the question of whether it is simply or multiply connected. Several authors have investigated whether the topology of a multiconnected hyperbolic universe would be detectable when 0.9<Ω<1. However, the possibility of detecting a given topology varies depending on the location of the observer within the space. Recent studies have assumed the observer sits at a favorable location. The present paper extends that work to consider observers at all points in the space, and (for given values of Ωm and ΩΛ and a given topology) computes the probability that a randomly placed observer could detect the topology. The computations show that when Ω=0.98 a randomly placed observer has a reasonable chance (~50%) of detecting a hyperbolic topology, but when Ω=0.99 the chances are low (<10%) and decrease still further as Ω approaches one.
TL;DR: In this article, the free spinor field on a fuzzy sphere is described within the Watamura approach to Dirac operator, and a simple gauge extension of the model with usual polynomial interaction is presented.
Abstract: The free spinor field on a fuzzy sphere is described within Watamura approach to Dirac operator. Except of the highest mode, its spectrum is the same but truncated as in the commutative case. We present a simple gauge extension of the model with usual polynomial interaction. The gauge symmetry is exact, and the chiral properties of the field modes are standard except the highest mode.
TL;DR: In the heavy quark limit, the valence Fock-state components in the B mesons are described by a set of two light-cone wave functions as mentioned in this paper, which are based on the equations of motion in the Heavy Quark Effective Theory (HQET).
Abstract: In the heavy-quark limit, the valence Fock-state components in the B mesons are described by a set of two light-cone wave functions. We show that these two wave functions obey simple coupled differential equations, which are based on the equations of motion in the Heavy Quark Effective Theory (HQET), and the analytic solutions for them are obtained. The results generalize the recently obtained longitudinal-momentum distribution in the Wandzura–Wilczek approximation by including the transverse momenta. We find that the transverse momentum distribution depends on the longitudinal momentum of the constituents, and that the wave functions damp very slowly for large transverse separation between quark and antiquark.
TL;DR: In this paper, the propagation of Dirac neutrinos in gravitational background was studied and it was shown that the gravitational interaction can lead to neutrino asymmetry due to modifications in dispersion relation.
Abstract: We study the propagation of Dirac neutrinos in gravitational backgrounds and show that the gravitational interaction can lead to neutrino asymmetry due to modifications in dispersion relation. We give some examples of spacetime geometries where such asymmetry can arise. This asymmetry would have contributed to the relic neutrino asymmetry through the interaction of neutrinos with primordial black holes before neutrinos decoupled. In the present epoch it may be generated in accretion around high temperature rotating black holes.
TL;DR: In this article, the authors studied matrix models related to SO/Sp gauge theories with flavors and derived the Seiberg-Witten curve for these theories from matrix model argument.
Abstract: We study matrix models related to SO/Sp gauge theories with flavors. We give the effective superpotentials for gauge theories with arbitrary tree level superpotential up to first instanton level. For quartic tree level superpotential, we obtained exact one-cut solution. We also derive Seiberg–Witten curve for these gauge theories from matrix model argument.
TL;DR: In this article, a possibility to construct an SU(1,1|2) invariant extension of the Calogero model is considered and the two-particle case is treated in detail.
Abstract: Recently it was conjectured by Gibbons and Townsend that the large n limit of an N = 4 superconformal extension of the n-particle Calogero model might provide a microscopic description of the extreme Reissner–Nordstrom black hole near the horizon. In this paper a possibility to construct an SU(1,1|2) invariant extension of the Calogero model is considered. We treat in detail the two-particle case and comment on some peculiarities intrinsic to n > 2 generalizations.
TL;DR: In this article, the authors investigate the dynamics of particles moving in a spacetime augmented by one extra dimension in the context of the induced matter theory of gravity and examine the appearance of a fifth force as an effect caused by the extra dimension.
Abstract: We investigate the dynamics of particles moving in a spacetime augmented by one extra dimension in the context of the induced matter theory of gravity. We examine the appearance of a fifth force as an effect caused by the extra dimension and discuss two different approaches to the fifth force formalism. We then give two simple examples of application of both approaches by considering the case of a Ricci-flat warped-product manifold and a generalized Randall–Sundrum space.
TL;DR: In this article, the authors analyzed ghost condensates of dimension two in a class of nonlinear nonlinear gauges in pure Yang-Mills theories, related to the breaking of the SL(2, R) symmetry, present in these gauges.
Abstract: Ghost condensates of dimension two are analyzed in a class of nonlinear gauges in pure Yang–Mills theories. These condensates are related to the breaking of the SL(2, R) symmetry, present in these gauges.
TL;DR: In this article, the authors studied the wave equation for a minimally coupled massive scalar in three-dimensional de Sitter space and computed the absorption cross-section to investigate its cosmological horizon in the southern diamond.
Abstract: We study the wave equation for a minimally coupled massive scalar in three-dimensional de Sitter space. We compute the absorption cross-section to investigate its cosmological horizon in the southern diamond. Although the absorption cross-section is not defined exactly, it can be determined from the fact that the low-energy s(j = 0)-wave absorption cross-section for a massless scalar is given by the area of the cosmological horizon. On the other hand, the low-temperature limit of j ≠ 0-mode absorption cross-section is useful for extracting information surrounding the cosmological horizon. Finally we mention a computation of the absorption cross-section on the CFT-side using the dS/CFT correspondence.
TL;DR: In this paper, the authors construct specific examples in which the curvature corresponding gab(xi;λ) becomes a Dirac delta function and gets concentrated on the horizon when the limit λ→0 is taken, but the action remains finite.
Abstract: A class of metrics gab(xi) describing spacetimes with horizons (and associated thermodynamics) can be thought of as a limiting case of a family of metrics gab(xi;λ)without horizons when λ→0. We construct specific examples in which the curvature corresponding gab(xi;λ) becomes a Dirac delta function and gets concentrated on the horizon when the limit λ→0 is taken, but the action remains finite. When the horizon is interpreted in this manner, one needs to remove the corresponding surface from the Euclidean sector, leading to winding numbers and thermal behavior. In particular, the Rindler spacetime can be thought of as the limiting case of (horizon-free) metrics of the form [g00=e2+a2x2; gμν=-δμν] or [g00=-gxx=(e2+4a2x2)1/2, gyy=gzz=-1] when e→0. In the Euclidean sector, the curvature gets concentrated on the origin of tE-x plane in a manner analogous to Aharanov–Bohm effect (in which the vector potential is a pure gauge everywhere except at the origin) and the curvature at the origin leads to nontrivial topological features and winding number.
TL;DR: In this paper, an SU(N)M quiver gauge theory with three chiral families was proposed to accommodate the standard model and unify all of SU(3)C, SU(2)L and U(1)Y couplings at one unique scale estimated as M ≃ 4 TeV.
Abstract: We show how an SU(N)M quiver gauge theory can accommodate the standard model with three chiral families and unify all of SU(3)C, SU(2)L and U(1)Y couplings with high accuracy at one unique scale estimated as M ≃ 4 TeV.
TL;DR: In this paper, high energy elastic pp scattering at the Large Hadron Collider (LHC) at c.m. energy 14 TeV is predicted using the asymptotic behavior of σtot(s) and ρ(s), known from dispersion relation calculations and the measured elastic differential cross-section at $\sqrt{s}=546~{\rm GeV}$.
Abstract: High energy elastic pp scattering at the Large Hadron Collider (LHC) at c.m. energy 14 TeV is predicted using the asymptotic behavior of σtot(s) and ρ(s) known from dispersion relation calculations and the measured elastic $\bar{p}p$ differential cross-section at $\sqrt{s}=546~{\rm GeV}$. The effective field theory model underlying the phenomenological analysis describes the nucleon as having an outer cloud of quark–antiquark condensed ground state, an inner core of topological baryonic charge of radius ≃ 0.44 F and a still smaller valence quark-bag of radius ≲ 0.1 F. The LHC experiment TOTEM (Total and Elastic Measurement), if carried out with sufficient precision from |t| = 0 to |t| > 10 GeV2, will be able to test this structure of the nucleon.
TL;DR: In this paper, the twisting function describing a nonstandard (super-Jordanian) quantum deformation of osp(1|2) is given in explicit closed form, and the quantum coproducts and universal R-matrix are presented.
Abstract: The twisting function describing a nonstandard (super-Jordanian) quantum deformation of osp(1|2) is given in explicit closed form. The quantum coproducts and universal R-matrix are presented. The non-uniqueness of the twisting function as well as two real forms of the deformed osp(1|2) superalgebras are considered. One real quantum osp(1|2) superalgebra is interpreted as describing the κ-deformation of D = 1, N = 1 superconformal algebra, which can be applied as a symmetry algebra of N = 1 superconformal mechanics.
TL;DR: In this paper, the authors analyzed the topological charge of general non-commutative U(N) instantons using the Corrigan's identity and found that the result is exactly the instanton number k, which appears in the non-Commutative ADHM construction as the dimension of the vector space V. This result coincides with the corresponding fact in the commutative case.
Abstract: We analytically calculate the topological charge of general noncommutative U(N) instantons using the Corrigan's identity and find that the result is exactly the instanton number k, which appears in the noncommutative ADHM construction as the dimension of the vector space V. This result coincides with the corresponding fact in the commutative case.