Showing papers in "International Journal of Modern Physics A in 2008"
TL;DR: In this article, a quark model is applied to the spectrum of baryons containing heavy quarks, and the model gives masses for the known heavy quark that are in agreement with experiment, but for the doubly-charmed baryon Ξcc, the model prediction is too heavy.
Abstract: A quark model is applied to the spectrum of baryons containing heavy quarks. The model gives masses for the known heavy baryons that are in agreement with experiment, but for the doubly-charmed baryon Ξcc, the model prediction is too heavy. Mixing between the ΞQ and Ξ′Q states is examined and is found to be small for the lowest lying states. In contrast with this, mixing between the Ξbc and Ξ′bc states is found to be large, and the implication of this mixing for properties of these states is briefly discussed. We also examine heavy-quark spin-symmetry multiplets, and find that many states in the model can be placed in such multiplets. We compare our predictions with those of a number of other authors.
363 citations
TL;DR: In this article, the existence and properties of a nontrivial fixed point in f(R)-gravity, where f is a polynomial of order up to six, were discussed.
Abstract: We discuss the existence and properties of a nontrivial fixed point in f(R)-gravity, where f is a polynomial of order up to six. Within this seven-parameter class of theories, the fixed point has three ultraviolet-attractive and four ultraviolet-repulsive directions; this brings further support to the hypothesis that gravity is nonperturbatively renormalizable.
260 citations
TL;DR: In this article, a detailed investigation of free scalar field theory on κ-Minkowski space is presented, and the Lagrangian and solutions of field equations are discussed in detail.
Abstract: This paper is devoted to detailed investigations of free scalar field theory on κ-Minkowski space. After reviewing necessary mathematical tools, we discuss in detail the Lagrangian and solutions of field equations. We analyze the space–time symmetries of the model and construct the conserved charges associated with translational and Lorentz symmetries. We show that the version of the theory usually studied breaks Lorentz invariance in a subtle way: there is an additional trans-Planckian mode present, and an associated conserved charge (the number of such modes) is not a Lorentz scalar.
107 citations
TL;DR: In this article, it was shown that practically all nucleons with momenta 300 MeV/c belong to SRCs, consisting mostly of two nucleons, and that a fast removal of such nucleon practically always leads to emission of correlated nucleon with approximately opposite momentum.
Abstract: Novel processes probing the decay of nucleus after removal of a nucleon with momentum larger than Fermi momentum by hard probes nally proved unambiguously the evidence for long sought presence of short-range correlations (SRCs) in nuclei. In combination with the analysis of large Q 2 , A(e,e’)X processes at x > 1 they allow us to conclude that (i) practically all nucleons with momenta 300 MeV/c belong to SRCs, consisting mostly of two nucleons, ii) probability of such SRCs in medium and heavy nuclei is 25%, iii) a fast removal of such nucleon practically always leads to emission of correlated nucleon with approximately opposite momentum, iv) proton removal from twonucleon SRCs in 90% of cases is accompanied by a removal of a neutron and only in 10% by a removal of another proton. We explain that observed absolute probabilities and the isospin structure of two nucleon SRCs conrm the
106 citations
TL;DR: In this article, a review of recent developments in understanding quantum/string corrections to BPS black holes and strings in five-dimensional supergravity is presented. And the off-shell formulation of this theory obtained through the conformal supergravity method and the methods for investigating supersymmetric solutions are reviewed.
Abstract: We review recent developments in understanding quantum/string corrections to BPS black holes and strings in five-dimensional supergravity. These objects are solutions to the effective action obtained from M-theory compactified on a Calabi–Yau threefold, including the one-loop corrections determined by anomaly cancellation and supersymmetry. We introduce the off-shell formulation of this theory obtained through the conformal supergravity method and review the methods for investigating supersymmetric solutions. This leads to quantum/string corrected attractor geometries, as well as asymptotically flat black strings and spinning black holes. With these solutions in hand, we compare our results with analogous studies in four-dimensional string-corrected supergravity, emphasizing the distinctions between the four- and five-dimensional theories.
104 citations
TL;DR: In this paper, the Pohlmeyer reduction of the GS superstring sigma model on AdS3 × S3 supported by RR flux is considered and the bosonic part of the reduced Lagrangian is given by the sum of the complex sine-Gordon Lagrangians and its sinh-Gordon counterpart.
Abstract: We review the Pohlmeyer reduction of the superstring sigma model on AdSn × Sn leading to a gauged WZW model with an integrable potential. In particular, we consider the case of GS superstrings on AdS3 × S3 supported by RR flux. The bosonic part of the reduced Lagrangian is given by the sum of the complex sine-Gordon Lagrangian and its sinh-Gordon counterpart. We determine the corresponding fermionic part and discuss possible 2d supersymmetry of the reduced action.
70 citations
TL;DR: In this paper, a survey of methods of measuring the spin of new physics particles at the Large Hadron Collider (LHC) can be found, focusing on the case in which a long-lived massive neutral particle is produced at the end of every cascade decay and escape detection.
Abstract: Spin measurement is crucial in distinguishing major scenarios of TeV scale new physics once it is discovered at the Large Hadron Collider (LHC). We give a brief survey of methods of measuring the spin of new physics particles at the LHC. We focus on the case in which a long lived massive neutral particle is produced at the end of every cascade decay and escape detection. This is the case for R-parity preserving supersymmetry, Little Higgs models with T-parity, extra-dimensional models with KK-parity, and a large class of similar models and scenarios. After briefly commenting on measuring spin by combining mass and rate information, we concentrate on direct measurement by observing angular correlations among decay products of the new physics particles. We survey a wide range of possible channels, discuss the construction of possible correlation variables, and outline experimental challenges. We also briefly survey the Monte Carlo tools which are useful in studying such correlations.
66 citations
TL;DR: In this article, the main identification between solitons and string spikes is reviewed and extended, and the inverse scattering technique is applied for reconstructing AdS string configurations from soliton solutions of sinh-Gordon theory.
Abstract: In this contribution we describe some soliton based techniques for generating classical AdS string solutions. The methods introduced are useful for further understanding of rotating AdS configurations with spikes which correspond to higher twist operators in SYM theory. The main identification (accomplished in arXiv:0712.1193) between solitons and string spikes is reviewed and extended. We desribe how inverse scattering technique can be applied for reconstructing AdS string configurations from soliton solutions of sinh-Gordon theory (in the example of AdS3).
65 citations
TL;DR: In this paper, the authors summarized underground and ground-based observations of solar cosmic rays (SCR) accumulated since 1942, direct spacecraft measurements of solar energetic particles (SEP) near the Earth's orbit, indirect information on the SCR variations in the past, and other relevant astrophysical, solar and geophysical data.
Abstract: This review paper comprises main concepts, available observational data and recent theoretical results related to astrophysical aspects of particle acceleration at/near the Sun and extreme capacities of the solar accelerator(s). We summarize underground and ground-based observations of solar cosmic rays (SCR) accumulated since 1942, direct spacecraft measurements of solar energetic particles (SEP) near the Earth's orbit, indirect information on the SCR variations in the past, and other relevant astrophysical, solar and geophysical data. The list of the problems under discussion includes: upper limit spectrum (ULS) for solar cosmic rays; maximum energy (rigidity), Em(Rm), of particles accelerated at/near the Sun; production of the flare neutrinos; energetics of SCR and solar flares; production of flare neutrons and gamma rays; charge states and elemental abundances of accelerated solar ions; coronal mass ejections (CME's) and extended coronal structures in acceleration models; magnetic reconnection in acceleration scenarios; size (frequency) distributions of solar proton events (SPE) and stellar flares; occurrence probability of giant flares; archaeology of solar cosmic rays. The discussion allows us to outline a series of interesting conceptual and physical associations of SCR generation with the high-energy processes at other stars. The most reliable estimates of various parameters are given in each of research fields mentioned above; a set of promising lines of future studies is highlighted. A great importance of SCR data for resolving some general astrophysical problems is emphasized.
64 citations
TL;DR: In this article, it was shown that the today estimated value of dark energy can be achieved by the vacuum condensate induced by neutrino mixing phenomenon, which is linked to the sub-eV neutrinos mass scale.
Abstract: We show that the today estimated value of dark energy can be achieved by the vacuum condensate induced by neutrino mixing phenomenon. The tiny value of dark energy is linked to the sub-eV neutrino mass scale. Contributions to dark energy from auxiliary fields or mechanisms are not necessary in this approach.
60 citations
TL;DR: In this paper, the main properties of the cosmological singularity associated with the homogeneous and inhomogeneous Mixmaster model are analyzed and a survey of the main results obtained over the last forty years on the Mixmaster topic is presented.
Abstract: This review paper is devoted to analyzing the main properties of the cosmological singularity associated with the homogeneous and inhomogeneous Mixmaster model. After the introduction of the main tools required to treat the cosmological issue, we review in detail the main results obtained over the last forty years on the Mixmaster topic. We first assess the classical picture of the homogeneous chaotic cosmologies and, after a presentation of the canonical method for the quantization, we develop the quantum Mixmaster behavior. Finally, we extend both the classical and the quantum features to the fully inhomogeneous case. Our survey analyzes the fundamental framework of the Mixmaster picture and completes it by accounting for recent and peculiar outstanding results.
TL;DR: In this paper, the authors examined a scenario where the Higgs boson is coupled to an additional Standard Model singlet scalar field from a hidden sector and obtained a feasible dark matter density.
Abstract: We examine a scenario where the Higgs boson is coupled to an additional Standard Model singlet scalar field from a hidden sector. We show that, in the case where this field is very light and has already relaxed to its nonzero vacuum expectation value, one gets a very stringent limit on the mixing angle between the hidden sector scalar and the Higgs field from fifth force experiments. However, this limit does not imply in a small coupling due to the large difference of vacuum expectation values. In the case that the hidden sector scalar is identified with the quintessence field, responsible for the recent acceleration of the universe, the most natural potential describing the interaction is disfavored since it results in a time-variation of the Fermi scale. We show that an ad hoc modification of the potential describing the Higgs interaction with the quintessence field may result in an unified picture of dark matter and dark energy, where dark energy is the zero-mode classical field rolling the usual quintessence potential and the dark matter candidate is the quantum excitation (particle) of the field, which is produced in the universe due to its coupling to the Higgs boson. This coupling also generates a mass for the new particle that, contrary to usual quintessence models, does not have to be small, since it does not affect the evolution of classical field. In this scenario, a feasible dark matter density can be, under conditions, obtained.
TL;DR: The bound state solutions of the Schrodinger equation for a second Poschl-Teller-like potential with the centrifugal term are obtained approximately in this paper, where the solutions can be expressed in terms of the hypergeometric functions 2F1(a, b, c, z).
Abstract: The bound state solutions of the Schrodinger equation for a second Poschl–Teller-like potential with the centrifugal term are obtained approximately. It is found that the solutions can be expressed in terms of the hypergeometric functions 2F1(a, b; c; z). To show the accuracy of our results, we calculate the eigenvalues numerically for arbitrary quantum numbers n and l. It is found that the results are in good agreement with those obtained by other method for short-range potential. Two special cases for l = 0 and V1 = V2 are also studied briefly.
TL;DR: H holographically derive entropy of (near) extremal black holes as entanglement entropy of conformal quantum mechanics(CQM) living in two boundaries of AdS2.
Abstract: We holographically derive entropy of (near) extremal black holes as entanglement entropy of conformal quantum mechanics(CQM) living in two boundaries of AdS2.
TL;DR: In this paper, the authors review the prospects for direct and indirect dark matter searches of Weakly Interacting Massive Particles in the dark halo of our galaxy and focus in particular on the data of GLAST, PAMELA and DAMA.
Abstract: The search for dark matter is a very wide and active field of research, and I necessarily concentrate here only in some aspects of it. I will review the prospects for direct and indirect dark matter searches of Weakly Interacting Massive Particles in the dark halo of our galaxy and focus in particular on the data of GLAST, PAMELA and DAMA.
TL;DR: In this article, the asymptotic iteration method (AIM) is applied to obtain highly accurate eigenvalues of the radial Schrodinger equation with the singular potential V(r) = r2+λ/rα(α,λ>0) in arbitrary dimensions.
Abstract: The asymptotic iteration method (AIM) is applied to obtain highly accurate eigenvalues of the radial Schrodinger equation with the singular potential V(r) = r2+λ/rα(α,λ>0) in arbitrary dimensions. Certain fundamental conditions for the application of AIM, such as a suitable asymptotic form for the wave function, and the termination condition for the iteration process, are discussed. Several suggestions are introduced to improve the rate of convergence and to stabilize the computation. AIM offers a simple, accurate, and efficient method for the treatment of singular potentials, such as V(r), valid for all ranges of coupling λ.
TL;DR: In this paper, it was shown that from the R2 high order gravity theory it is possible to produce, in the linearized approach, particles which can be seen as massive modes of gravitational waves (GW's).
Abstract: We show that from the R2 high order gravity theory it is possible to produce, in the linearized approach, particles which can be seen as massive modes of gravitational waves (GW's). The presence of the mass generates a longitudinal force in addition of the transverse one which is proper of the massless gravitational waves and the response an interferometer to the effect is computed. This could be, in principle, important to discriminate among the gravity theories. The presence of the mass could also have important applications in cosmology because the fact that gravitational waves can have mass could give a contribution to the dark matter of the Universe.
TL;DR: In this paper, the averaged Einstein equations of macroscopic gravity are modified on cosmological scales by the macro-scopic gravitational correlation tensor terms as compared with the Einstein equation of general relativity.
Abstract: The averaging problem in cosmology and the approach of macroscopic gravity to resolve the problem is discussed. The averaged Einstein equations of macroscopic gravity are modified on cosmological scales by the macroscopic gravitational correlation tensor terms as compared with the Einstein equations of general relativity. This correlation tensor satisfies a system of structure and field equations. An exact cosmological solution to the macroscopic gravity equations for a constant macroscopic gravitational connection correlation tensor for a flat spatially homogeneous, isotropic macroscopic space-time is presented. The correlation tensor term in the macroscopic Einstein equations has been found to take the form of either a negative or positive spatial curvature term. Thus, macroscopic gravity provides a cosmological model for a flat spatially homogeneous, isotropic Universe which obeys the dynamical law for either an open or closed Universe.
TL;DR: In this article, an introductory review of quantum physics on the Groenewold-Moyal plane is given, where basic ideas like star products, twisted statistics, second quantized fields and discrete symmetries are discussed.
Abstract: We give an introductory review of quantum physics on the noncommutative space–time called the Groenewold–Moyal plane. Basic ideas like star products, twisted statistics, second quantized fields and discrete symmetries are discussed. We also outline some of the recent developments in these fields and mention where one can search for experimental signals.
TL;DR: In this article, the one-loop electroweak expression of diagonal and nondiagonal stop-antistop and sbottom-antisbottom production from initial state gluons at LHC was computed.
Abstract: We have computed the one-loop electroweak expression of diagonal and nondiagonal stop–antistop and sbottom–antisbottom production from initial state gluons at LHC We have investigated the possibility that the one-loop effects exhibit a dependence on "extra" supersymmetric parameters different from the final squark masses Our results, given for a choice of twelve SUSY benchmark points in the MSSM with mSUGRA symmetry breaking, show that in some cases a mild dependence might arise, at the percent relative level, of not simple experimental detection
TL;DR: In this article, the authors summarize the expectations for top-quark physics at the Large Hadron Collider, and outline new physics scenarios in which the top quark is crucially involved.
Abstract: The LHC (Large Hadron Collider) will be a top-quark factory. With 80 million pairs of top quarks and an additional 34 million single tops produced annually at the designed high luminosity, the properties of this particle will be studied to a great accuracy. The fact that the top quark is the heaviest elementary particle in the Standard Model with a mass right at the electroweak scale makes it tempting to contemplate its role in electroweak symmetry breaking, as well as its potential as a window to unknown new physics at the TeV scale. We summarize the expectations for top-quark physics at the LHC, and outline new physics scenarios in which the top quark is crucially involved.
TL;DR: In this paper, new quantum modes of the free scalar field are derived in a special time-evolution picture that may be introduced in moving charts of de Sitter backgrounds, and the wave functions of these new modes are solutions of the Klein-Gordon equation and energy eigenfunctions, defining the energy basis.
Abstract: New quantum modes of the free scalar field are derived in a special time-evolution picture that may be introduced in moving charts of de Sitter backgrounds. The wave functions of these new modes are solutions of the Klein–Gordon equation and energy eigenfunctions, defining the energy basis. This completes the scalar quantum mechanics where the momentum basis is well known for long time. In this enlarged framework the quantization of the scalar field can be done in canonical way obtaining the principal conserved one-particle operators and the Green functions.
TL;DR: In this paper, the model of radiative neutrino mass with dark matter proposed by one of us is extended to include a real singlet scalar field, and two important new consequences are then discussed.
Abstract: The model of radiative neutrino mass with dark matter proposed by one of us is extended to include a real singlet scalar field. There are then two important new consequences. One is the realistic possibility of having the lightest neutral singlet fermion (instead of the lightest neutral component of the dark scalar doublet) as the dark matter of the universe. The other is a modification of the effective Higgs potential of the Standard Model, consistent with electroweak baryogenesis.
TL;DR: In this article, the problem of a spherically symmetric charged thin shell of dust collapsing gravitationally into a charged Reissner-Nordstrom black hole in d space-time dimensions is studied within the theory of general relativity.
Abstract: The problem of a spherically symmetric charged thin shell of dust collapsing gravitationally into a charged Reissner–Nordstrom black hole in d space–time dimensions is studied within the theory of general relativity. Static charged shells in such a background are also analyzed. First, a derivation of the equation of motion of such a shell in a d-dimensional space–time is given. Then, a proof of the cosmic censorship conjecture in a charged collapsing framework is presented, and a useful constraint which leads to an upper bound for the rest mass of a charged shell with an empty interior is derived. It is also proved that a shell with total mass equal to charge, i.e. an extremal shell, in an empty interior, can only stay in neutral equilibrium outside its gravitational radius. This implies that it is not possible to generate a regular extremal black hole by placing an extremal dust thin shell within its own gravitational radius. Moreover, it is shown, for an empty interior, that the rest mass of the shell is limited from above. Then, several types of behavior of oscillatory charged shells are studied. In the presence of a horizon, it is shown that an oscillatory shell always enters the horizon and reemerges in a new asymptotically flat region of the extended Reissner–Nordstrom space–time. On the other hand, for an overcharged interior, i.e. a shell with no horizons, an example showing that the shell can achieve a stable equilibrium position is presented. The results presented have applications in brane scenarios with extra large dimensions, where the creation of tiny higher-dimensional charged black holes in current particle accelerators might be a real possibility, and generalize to higher dimensions previous calculations on the dynamics of charged shells in four dimensions.
TL;DR: In this article, the authors analyzed the long-range correlation property and the corresponding multifractal structure of the distribution of shower particles in central Au + Au collisions at 200 A GeV by using the Multifractal Detrended Fluctuation Analysis method.
Abstract: This paper analyzes the long-range correlation property and the corresponding multifractal structure of the distribution of shower particles in central Au + Au collisions at 200 A GeV by using the Multifractal Detrended Fluctuation Analysis method. The result shows that the pseudorapidity and azimuthal distributions of shower particles are multifractals in those collisions.
TL;DR: In this paper, it was shown that spontaneous breaking of diffeomorphism invariance results in gravitational Higgs mechanism in space-time dimensions D ≤ 10, which coincides with the critical dimension of superstring theory.
Abstract: In Modern Physics Letters A15, 2265 (2000), in the context of domain wall backgrounds, it was shown that spontaneous breaking of diffeomorphism invariance results in gravitational Higgs mechanism. Recently in arXiv:0708.3184 't Hooft discussed gravitational Higgs mechanism in the context of obtaining massive gravity directly in four dimensions, and pointed out some subtleties with unitarity. We attribute these subtleties to breaking timelike diffeomorphisms, and discuss gravitational Higgs mechanism with all but timelike diffeomorphisms spontaneously broken. The resulting background is no longer flat but exhibits expansion, which is linear in time. For space–time dimensions D ≤ 10 the background is stable and has no nonunitary propagating modes. The absence of nonunitary modes is due to the unbroken timelike diffeomorphism invariance. The physical states correspond to those of a massive graviton. The effective mass squared of the graviton is positive for D 10 the graviton modes become effectively tachyonic. The special value of D = 10, which coincides with the critical dimension of superstring theory, arises in our setup completely classically.
TL;DR: In this article, an algebraic understanding of the inequivalent connectivities of the graphs associated to the irreducible supermultiplets of the N-extended supersymmetric quantum mechanics is provided.
Abstract: We furnish an algebraic understanding of the inequivalent connectivities (computed up to N ≤ 10) of the graphs associated to the irreducible supermultiplets of the N-extended supersymmetric quantum mechanics. We prove that the inequivalent connectivities of the N = 5 and N = 9 irreducible supermultiplets are due to inequivalent decompositions into two sets of N = 4 (respectively, N = 8) supermultiplets. "Oxido-reduction" diagrams linking the irreducible supermultiplets of the N = 5, 6, 7, 8 supersymmetries are presented. We briefly discuss these results and their possible applications.
TL;DR: In this article, the authors derived the EOS of QCD at finite chemical potential and zero temperature using the rainbow-ladder approximation of the Dyson-Schwinger approach, where the pressure density is the sum of two terms: the first term (the pressure density at μ = 0) is a μ-independent constant; the second term is totally determined by G[μ](p) (the dressed quark propagator at finite μ), which contains all the nontrivial μ-dependence.
Abstract: In this paper, we give a direct method for calculating the partition function, and hence the equation of state (EOS) of QCD at finite chemical potential and zero temperature. In the EOS derived in this paper, the pressure density is the sum of two terms: the first term (the pressure density at μ = 0) is a μ-independent constant; the second term, which is totally determined by G[μ](p) (the dressed quark propagator at finite μ), contains all the nontrivial μ-dependence. By applying a general result in the rainbow-ladder approximation of the Dyson–Schwinger approach obtained in our previous study, Phys. Rev. C71, 015205 (2005), G[μ](p) is calculated from the model quark propagator proposed in Phys. Rev. D20, 2947 (1979). From this the full analytic expression of the EOS of QCD at finite μ and zero T is obtained. A comparison between our EOS and the cold, perturbative EOS of QCD of Fraga, Pisarski and Schaffner-Bielich is made. It is expected that our EOS can provide a possible new approach for the study of neutron stars. In the final part of this paper, our method is generalized to the case of finite temperature and the EOS of QCD at finite μ and T is derived. A comparison is made between the EOS derived in this paper and the EOS obtained in previous literatures by directly generalizing the CJT effective action at μ = 0 and T = 0 to finite μ and finite T.
TL;DR: In this paper, the full group of approximate mass degeneracies is argued to be SU(2)f × I × O(4), where I is the degeneracy of isosinglets and isotriplets, and O (4) is the group of the relativistic hydrogen atom.
Abstract: The recent experimental results on the spectrum of highly excited light nonstrange mesons are known to reveal a high degree of degeneracy among different groups of states. We revise some suggestions about the nature of the phenomenon and put the relevant ideas into the final shape. The full group of approximate mass degeneracies is argued to be SU(2)f × I × O(4), where I is the degeneracy of isosinglets and isotriplets and O(4) is the degeneracy group of the relativistic hydrogen atom. We discuss the dynamical origin and consequences of considered symmetry with a special emphasis on distinctions of this symmetry from the so-called chiral symmetry restoration scenario.
TL;DR: In this paper, a spatially homogeneous and anisotropic Bianchi type-I space-time has been studied within the framework of Lyra's geometry, and exact solutions of the Einstein's field equations have been obtained with a time dependent gauge function by using a special law of variation for Hubble's parameter that yields a constant value of deceleration parameter.
Abstract: A spatially homogeneous and anisotropic Bianchi type-I space–time has been studied within the framework of Lyra's geometry. Exact solutions of the Einstein's field equations have been obtained with a time dependent gauge function by using a special law of variation for Hubble's parameter that yields a constant value of deceleration parameter. It has been found that the solutions generalize the solutions obtained by Rahaman et al. [Astrophys. Space Sci.299, 211 (2005)] and are consistent with the recent observations of type Ia supernovae. A detailed study of physical and kinematical properties of the model has been carried out.