Gravitational collapse of charged scalar fields
Torres, Jose M
2014-01-01
In order to study the gravitational collapse of charged matter we analyze the simple model of an self-gravitating massless scalar field coupled to the electromagnetic field in spherical symmetry. The evolution equations for the Maxwell-Klein-Gordon sector are derived in the 3+1 formalism, and coupled to gravity by means of the stress-energy tensor of these fields. To solve consistently the full system we employ a generalized Baumgarte-Shapiro-Shibata-Nakamura (BSSN) formulation of General Relativity that is adapted to spherical symmetry. We consider two sets of initial data that represent a time symmetric spherical thick shell of charged scalar field, and differ by the fact that one set has zero global electrical charge while the other has non-zero global charge. For compact enough initial shells we find that the configuration doesn't disperse and approaches a final state corresponding to a sub-extremal Reissner-N\\"ordstrom black hole with $|Q|
Charged Scalars in Transient Stellar Electromagnetic Fields
Institute of Scientific and Technical Information of China (English)
Marina-Aura Dariescu; Ciprian Dariescu; Ovidiu Buhucianu
2011-01-01
We consider a non-rotating strongly magnetized object, whose magnetic induction isof the form Bx = Bo{t)sin kz. In the electromagnetic field generated by only one component of the four-vector potential, we solve the Klein-Gordon equation and discuss the sudden growth of the scalar wave functions for wavenumbers inside computable ranges. In the case of unexcited transversal kinetic degrees, we write down the recurrent differential system for the amplitude functions and compute the respective conserved currents.
Charged Scalars in Transient Stellar Electromagnetic Fields
International Nuclear Information System (INIS)
We consider a non-rotating strongly magnetized object, whose magnetic induction is of the form Bx = B0(t)sinκZ. In the electromagnetic field generated by only one component of the four-vector potential, we solve the Klein—Gordon equation and discuss the sudden growth of the scalar wave functions for wavenumbers inside computable ranges. In the case of unexcited transversal kinetic degrees, we write down the recurrent differential system for the amplitude functions and compute the respective conserved currents. (general)
Black hole solutions in Einstein-charged scalar field theory
Ponglertsakul, S.; Dolan, S.; Winstanley, E.
2015-01-01
We investigate possible end-points of the superradiant instability for a charged black hole with a reflecting mirror. By considering a fully coupled system of gravity and a charged scalar field, hairy black hole solutions are obtained. The linear stability of these black hole solutions is studied.
Conserved Charges of Minimal Massive Gravity Coupled to Scalar Field
Setare, M R
2016-01-01
Recently, the theory of Topologically massive gravity non-minimally coupled to a scalar field has been proposed which comes from Lorentz-Chern-Simons theory \\cite{1}. That theory is a torsion free one. We extend that theory by adding an extra term which makes torsion to be non-zero. The extended theory can be regarded as an extension of Minimal massive gravity such that it is non-minimally coupled to a scalar field. We obtain equations of motion of extended theory such that they are expressed in terms of usual torsion free spin-connection. We show that BTZ spacetime is a solution of this theory when scalar field is constant. We define quasi-local conserved charge by the concept of generalized off-shell ADT current which both are conserved for any asymptotically Killing vector field as well as a Killing vector field which is admitted by spacetime everywhere. Also we find general formula for entropy of stationary black hole solution in the context of considered theory. We apply the obtained formulas on BTZ blac...
Instability of charged wormholes supported by a ghost scalar field
International Nuclear Information System (INIS)
In previous work, we analyzed the linear and nonlinear stability of static, spherically symmetric wormhole solutions to Einstein's field equations coupled to a massless ghost scalar field. Our analysis revealed that all these solutions are unstable with respect to linear and nonlinear spherically symmetric perturbations and showed that the perturbation causes the wormholes to either decay to a Schwarzschild black hole or undergo a rapid expansion. Here, we consider charged generalization of the previous models by adding to the gravitational and ghost scalar field an electromagnetic one. We first derive the most general static, spherically symmetric wormholes in this theory and show that they give rise to a four-parameter family of solutions. This family can be naturally divided into subcritical, critical and supercritical solutions depending on the sign of the sum of the asymptotic masses. Then, we analyze the linear stability of these solutions. We prove that all subcritical and all critical solutions possess one exponentially in time growing mode. It follows that all subcritical and critical wormholes are linearly unstable. In the supercritical case we provide numerical evidence for the existence of a similar unstable mode.
Einstein-charged scalar field theory: black hole solutions and their stability
Ponglertsakul, Supakchai; Dolan, Sam; Winstanley, Elizabeth(Consortium for Fundamental Physics, School of Mathematics and Statistics, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH, United Kingdom)
2015-01-01
A complex scalar field on a charged black hole in a cavity is known to experience a superradiant instability. We investigate possible final states of this instability. We find hairy black hole solutions of a fully coupled system of Einstein gravity and a charged scalar field. The black holes are surrounded by a reflecting mirror. We also investigate the stability of these black holes.
Massive Scalar Field Evolution in the Dyadosphere Spacetime of Charged Black Hole
International Nuclear Information System (INIS)
Scalar field quasinormal modes in the dyadosphere spacetime of charged black hole are studied by using the third-order WKB approximation. From numerical results obtained, we find that the scalar field mass u plays an important role in studying the quasinormal frequencies. With the scalar field mass increases, the real parts increase and the magnitudes of the imaginary parts decrease. Particulary, these change are almost linearly. (geophysics, astronomy, and astrophysics)
Dark sector impact on gravitational collapse of an electrically charged scalar field
Nakonieczna, Anna; Rogatko, Marek; Nakonieczny, Łukasz
2015-11-01
Dark matter and dark energy are dominating components of the Universe. Their presence affects the course and results of processes, which are driven by the gravitational interaction. The objective of the paper was to examine the influence of the dark sector on the gravitational collapse of an electrically charged scalar field. A phantom scalar field was used as a model of dark energy in the system. Dark matter was modeled by a complex scalar field with a quartic potential, charged under a U(1)-gauge field. The dark components were coupled to the electrically charged scalar field via the exponential coupling and the gauge field-Maxwell field kinetic mixing, respectively. Complete non-linear simulations of the investigated process were performed. They were conducted from regular initial data to the end state, which was the matter dispersal or a singularity formation in a spacetime. During the collapse in the presence of dark energy dynamical wormholes and naked singularities were formed in emerging spacetimes. The wormhole throats were stabilized by the violation of the null energy condition, which occurred due to a significant increase of a value of the phantom scalar field function in its vicinity. The square of mass parameter of the dark matter scalar field potential controlled the formation of a Cauchy horizon or wormhole throats in the spacetime. The joint impact of dark energy and dark matter on the examined process indicated that the former decides what type of an object forms, while the latter controls the amount of time needed for the object to form. Additionally, the dark sector suppresses the natural tendency of an electrically charged scalar field to form a dynamical Reissner-Nordström spacetime during the gravitational collapse.
Dark sector impact on gravitational collapse of an electrically charged scalar field
Nakonieczna, Anna; Nakonieczny, Łukasz
2015-01-01
Dark matter and dark energy are dominating components of the Universe. Their presence affects the course and results of processes, which are driven by the gravitational interaction. The objective of the paper was to examine the influence of the dark sector on the gravitational collapse of an electrically charged scalar field. A phantom scalar field was used as a model of dark energy in the system. Dark matter was modeled by a complex scalar field with a quartic potential, charged under an U(1)-gauge field. The dark components were coupled to the electrically charged scalar field via the exponential coupling and the gauge field-Maxwell field kinetic mixing, respectively. Complete non-linear simulations of the investigated process were performed. They were conducted from regular initial data to the end state, which was the matter dispersal or a singularity formation in a spacetime. During the collapse in the presence of dark energy dynamical wormholes and naked singularities were formed in emerging spacetimes. ...
Stability of black holes in Einstein-charged scalar field theory in a cavity
Dolan, Sam R; Winstanley, Elizabeth
2015-01-01
Can a black hole that suffers a superradiant instability evolve towards a 'hairy' configuration which is stable? We address this question in the context of Einstein-charged scalar field theory. First, we describe a family of static black hole solutions which possess charged scalar-field hair confined within a mirror-like boundary. Next, we derive a set of equations which govern the linear, spherically symmetric perturbations of these hairy solutions. We present numerical evidence which suggests that, unlike the vacuum solutions, the (single-node) hairy solutions are stable under linear perturbations. Thus, it is plausible that stable hairy black holes represent the end-point of the superradiant instability of electrically-charged Reissner-Nordstrom black holes in a cavity; we outline ways to explore this hypothesis.
The charged black-hole bomb: A lower bound on the charge-to-mass ratio of the explosive scalar field
Hod, Shahar
2016-01-01
The well-known superradiant amplification mechanism allows a charged scalar field of proper mass $\\mu$ and electric charge $q$ to extract the Coulomb energy of a charged Reissner-Nordstr\\"om black hole. The rate of energy extraction can grow exponentially in time if the system is placed inside a reflecting cavity which prevents the charged scalar field from escaping to infinity. This composed black-hole-charged-scalar-field-mirror system is known as the {\\it charged black-hole bomb}. Previous...
The charged black-hole bomb: A lower bound on the charge-to-mass ratio of the explosive scalar field
Shahar Hod
2016-01-01
The well-known superradiant amplification mechanism allows a charged scalar field of proper mass μ and electric charge q to extract the Coulomb energy of a charged Reissner–Nordström black hole. The rate of energy extraction can grow exponentially in time if the system is placed inside a reflecting cavity which prevents the charged scalar field from escaping to infinity. This composed black-hole-charged-scalar-field-mirror system is known as the charged black-hole bomb. Previous numerical stu...
Scalar fields versus black holes
International Nuclear Information System (INIS)
It is shown that if a body is endowed with a scalar charge, the event horizon associated with the modified Schwarzchild solution is reduced to a point, this avoiding the black holes formation. The discussion is restricted to ordinary scalar fields and conformally invariant scalar fields, respectively. (authors)
The charged black-hole bomb: A lower bound on the charge-to-mass ratio of the explosive scalar field
Hod, Shahar
2016-04-01
The well-known superradiant amplification mechanism allows a charged scalar field of proper mass μ and electric charge q to extract the Coulomb energy of a charged Reissner-Nordström black hole. The rate of energy extraction can grow exponentially in time if the system is placed inside a reflecting cavity which prevents the charged scalar field from escaping to infinity. This composed black-hole-charged-scalar-field-mirror system is known as the charged black-hole bomb. Previous numerical studies of this composed physical system have shown that, in the linearized regime, the inequality q / μ > 1 provides a necessary condition for the development of the superradiant instability. In the present paper we use analytical techniques to study the instability properties of the charged black-hole bomb in the regime of linearized scalar fields. In particular, we prove that the lower bound q/μ >√{rm/r- - 1/rm /r+ - 1 frac>} provides a necessary condition for the development of the superradiant instability in this composed physical system (here r± are the horizon radii of the charged Reissner-Nordström black hole and rm is the radius of the confining mirror). This analytically derived lower bound on the superradiant instability regime of the composed black-hole-charged-scalar-field-mirror system is shown to agree with direct numerical computations of the instability spectrum.
Vacuum pair production of charged scalar bosons in time-dependent electric fields
Li, Zi-Liang; Xie, Bai-Song
2013-01-01
Based on the quantum mechanical scattering model, the dynamical assist effect and the multiple-slit interference effect in electron-positron pair production from vacuum are generalized to vacuum pair production of charged scalar bosons. For the former effect some combinations of a strong but slowly varying electric field and a weak but rapidly varying one with different time delay are studied. Results indicate that the oscillation intensity of momentum spectrum and the number density of created bosons reduce with increasing of the time delay. Obviously, they achieve the maximum if the time delay equals zero. For the latter effect, it is shown that this effect does not exist for equal-sign $N$-pulse electric field in contrast to its existence for alternating-sign $N$-pulse. An approximate solution of boson momentum spectrum is got and it is agreeable well with the exact numerical one in alternating-sign $N$-pulse electric field, especially for $2$-pulse field and for small longitudinal momentum. The difference...
The charged black-hole bomb: A lower bound on the charge-to-mass ratio of the explosive scalar field
Hod, Shahar
2016-01-01
The well-known superradiant amplification mechanism allows a charged scalar field of proper mass $\\mu$ and electric charge $q$ to extract the Coulomb energy of a charged Reissner-Nordstr\\"om black hole. The rate of energy extraction can grow exponentially in time if the system is placed inside a reflecting cavity which prevents the charged scalar field from escaping to infinity. This composed black-hole-charged-scalar-field-mirror system is known as the {\\it charged black-hole bomb}. Previous numerical studies of this composed physical system have shown that, in the linearized regime, the inequality $q/\\mu>1$ provides a necessary condition for the development of the superradiant instability. In the present paper we use analytical techniques to study the instability properties of the charged black-hole bomb in the regime of linearized scalar fields. In particular, we prove that the lower bound ${{q}\\over{\\mu}}>\\sqrt{{{r_{\\text{m}}/r_--1}\\over{r_{\\text{m}}/r_+-1}}}$ provides a necessary condition for the develo...
Spinelly, J
2003-01-01
In this paper we consider a charged massless scalar quantum field operator in the spacetime of an idealized cosmic string, i.e., an infinitely long, straight and static cosmic string, which presents a magnetic field confined in a cylindrical tube of finite radius. Three distinct situations are taking into account in this analysis: {\\it{i)}} a homogeneous field inside the tube, {\\it{ii)}} a magnetic field proportional to $1/r$ and {\\it{iii)}} a cylindrical shell with $\\delta$-function. In these three cases the axis of the infinitely long tube of radius $R$ coincides with the cosmic string. In order to study the vacuum polarization effects outside the tube, we explicitly calculate the Euclidean Green function associated with this system for the three above situations, considering points in the region outside the tube.
Institute of Scientific and Technical Information of China (English)
ZHANG Hong-Bao; CAO Zhou-Jian; GAO Chong-Shou
2004-01-01
Si-Jie Gao has recently investigated Hawking radiation from spherically symmetrical gravitational collapse to an extremal R-N black hole for a real scalar field. Especially he estimated the upper bound for the expected number of particles in any wave packet belonging to Hout spontaneously produced from the state |0＞in, which confirms the traditional belief that extremal black holes do not radiate particles. Making some modifications, we demonstrate that the analysis can go through for a charged scalar field.
Nakonieczna, Anna
2016-01-01
Investigating the dynamics of gravitational systems, especially in the regime of quantum gravity, poses a problem of measuring time during the evolution. One of the approaches to this issue is using one of the internal degrees of freedom as a time variable. The objective of our research was to check whether a scalar field or any other dynamical quantity being a part of a coupled multi-component matter-geometry system can be treated as a `clock' during its evolution. We investigated a collapse of a self-gravitating electrically charged scalar field in the Einstein and Brans-Dicke theories using the 2+2 formalism. Our findings concentrated on the spacetime region of high curvature existing in the vicinity of the emerging singularity, which is essential for the quantum gravity applications. We investigated several values of the Brans-Dicke coupling constant and the coupling between the Brans-Dicke and the electrically charged scalar fields. It turned out that both evolving scalar fields and a function which meas...
International Nuclear Information System (INIS)
We investigate quasinormal modes of a massless charged scalar field on a small Reissner-Nordstroem-anti-de Sitter (RN-AdS) black hole both with analytical and numerical approaches. In the analytical approach, by using the small black hole approximation (r++/L→0, where r+ and L stand for the black hole event horizon radius and the AdS scale, respectively. We then show that the small RN-AdS black hole is unstable if its quasinormal modes satisfy the superradiance condition and that the instability condition of the RN-AdS black hole in the limit of r+/L→0 is given by Q>(3/eL)Qc, where Q, Qc, and e are the charge of the black hole, the critical (maximum) charge of the black hole, and the charge of the scalar field, respectively. In the numerical approach, we calculate the quasinormal modes for the small RN-AdS black holes with r++=0.2L, 0.1L, and 0.01L become unstable against scalar perturbations with eL=4 when the charge of the black hole satisfies Q > or approx. 0.8Qc, 0.78Qc, and 0.76Qc, respectively.
Matos, T; Urena-Lopez, L A; Núñez, D
2001-01-01
This work is a review of the last results of research on the Scalar Field Dark Matter model of the Universe at cosmological and at galactic level. We present the complete solution to the scalar field cosmological scenario in which the dark matter is modeled by a scalar field $\\Phi$ with the scalar potential $V(\\Phi)=V_{0}(cosh {(\\lambda \\sqrt{\\kappa_{0}}\\Phi)}-1)$ and the dark energy is modeled by a scalar field $\\Psi$, endowed with the scalar potential $\\tilde{V}(\\Psi)= \\tilde{V_{0}}(\\sinh{(\\alpha \\sqrt{\\kappa_{0}}\\Psi)})^{\\beta}$, which together compose the 95% of the total matter energy in the Universe. The model presents successfully deals with the up to date cosmological observations, and is a good candidate to treat the dark matter problem at the galactic level.
International Nuclear Information System (INIS)
In this paper, we consider a charged massless scalar quantum field operator in the spacetime of an idealized cosmic string, i.e., an infinitely long, straight and static cosmic string, which presents a magnetic field confined in a cylindrical tube of finite radius. Three distinct situations are taken into account in this analysis: (i) a homogeneous field inside the tube, (ii) a magnetic field proportional to 1/r and (iii) a cylindrical shell with δ-function. In these three cases, the axis of the infinitely long tube of radius R coincides with the cosmic string. In order to study the vacuum polarization effects outside the tube, we explicitly calculate the Euclidean Green function associated with this system for the three above situations, considering points in the region outside the tube. Having these Green functions we calculate the renormalized vacuum expectation values, { hat Φ * (x) hat Φ Ren and ( hat T ν μ (x) } Ren, associated with the charged field. In the evaluation of these vacuum polarization effects, two contributions appear for the three models. The first are the standard ones due to the conical geometry of the spacetime and the magnetic flux. The second contributions appear as extra terms. They are corrections due to the finite thickness of the radius of the tube. These extra terms provide relevant contributions, even for points very far away from the system, like a long-range effect
Structure Scalars In Charged Plane Symmetry
Sharif, M
2013-01-01
We consider non-adiabatic flow of the fluid possessing dissipation in the form of shearing viscosity in electromagnetic field. The scalar functions (structure scalars) for charged plane symmetry are formulated and are related with the physical variables of the fluid. We also develop a relationship between the Weyl tensor and other physical variables by using Taub mass formalism. The role of electric charge as well as its physical significance for the evolution of the shear tensor and expansion scalar are also explored. Finally, we discuss a special case for dust with cosmological constant.
Nakonieczna, Anna; Yeom, Dong-han
2016-05-01
Investigating the dynamics of gravitational systems, especially in the regime of quantum gravity, poses a problem of measuring time during the evolution. One of the approaches to this issue is using one of the internal degrees of freedom as a time variable. The objective of our research was to check whether a scalar field or any other dynamical quantity being a part of a coupled multi-component matter-geometry system can be treated as a `clock' during its evolution. We investigated a collapse of a self-gravitating electrically charged scalar field in the Einstein and Brans-Dicke theories using the 2+2 formalism. Our findings concentrated on the spacetime region of high curvature existing in the vicinity of the emerging singularity, which is essential for the quantum gravity applications. We investigated several values of the Brans-Dicke coupling constant and the coupling between the Brans-Dicke and the electrically charged scalar fields. It turned out that both evolving scalar fields and a function which measures the amount of electric charge within a sphere of a given radius can be used to quantify time nearby the singularity in the dynamical spacetime part, in which the apparent horizon surrounding the singularity is spacelike. Using them in this respect in the asymptotic spacetime region is possible only when both fields are present in the system and, moreover, they are coupled to each other. The only nonzero component of the Maxwell field four-potential cannot be used to quantify time during the considered process in the neighborhood of the whole central singularity. None of the investigated dynamical quantities is a good candidate for measuring time nearby the Cauchy horizon, which is also singular due to the mass inflation phenomenon.
Hod, Shahar
2016-01-01
We determine the characteristic timescales associated with the linearized relaxation dynamics of the composed Reissner-Nordstr\\"om-black-hole-charged-massive-scalar-field system. To that end, the quasinormal resonant frequencies $\\{\\omega_n(\\mu,q,M,Q)\\}_{n=0}^{n=\\infty}$ which characterize the dynamics of a charged scalar field of mass $\\mu$ and charge coupling constant $q$ in the charged Reissner-Nordstr\\"om black-hole spacetime of mass $M$ and electric charge $Q$ are determined {\\it analytically} in the eikonal regime $1\\ll M\\mu
Stationary Charged Scalar Clouds around Black Holes in String Theory
Bernard, Canisius
2016-01-01
It was reported that Kerr-Newman black holes can support linear charged scalar field in their exterior regions. This stationary massive charged scalar field can form a bound-state and these bound-states are called stationary scalar clouds. In this paper, we study that Kerr-Sen black holes can also support stationary massive charged scalar clouds by matching the near and far region solutions of the radial part of Klein-Gordon wave equation. We also review stationary scalar clouds within the background of static electrically charged black hole solution in the low energy limit of heterotic string field theory namely the GMGHS black holes.
International Nuclear Information System (INIS)
We discuss the extension of a version of quaternion quantum mechanics to field theory and in particular to the simplest example, the free scalar field. A previous difficulty with the conservation of four-momentum for the ''anomalous'' bosonic particles is resolved
Energy Technology Data Exchange (ETDEWEB)
De Leo, S. (Dipartimento di Fisica, Universita di Lecce, Lecce (Italy)); Rotelli, P. (Dipartimento di Fisica, Universita di Lecce e Sezione, Istituto Nazionale di Fisica Nucleare, Lecce (Italy))
1992-01-15
We discuss the extension of a version of {ital quaternion} quantum mechanics to field theory and in particular to the simplest example, the free scalar field. A previous difficulty with the conservation of four-momentum for the anomalous'' bosonic particles is resolved.
Charged scalar perturbations around a regular magnetic black hole
Huang, Yang; Liu, Dao-Jun
2016-05-01
We study charged scalar perturbations in the background of a regular magnetic black hole. In this case, the charged scalar perturbation does not result in superradiance. By using a careful time-domain analysis, we show that the charge of the scalar field can change the real part of the quasinormal frequency, but has little impact on the imaginary part of the quasinormal frequency and the behavior of the late-time tail. Therefore, the regular magnetic black hole may be stable under the perturbations of a charged scalar field at the linear level.
Directory of Open Access Journals (Sweden)
Shahar Hod
2015-07-01
Full Text Available The quasinormal resonance spectrum {ωn(μ,q,M,Q}n=0n=∞ of charged massive scalar fields in the charged Reissner–Nordström black-hole spacetime is studied analytically in the large-coupling regime qQ≫Mμ (here {μ,q} are respectively the mass and charge coupling constant of the field, and {M,Q} are respectively the mass and electric charge of the black hole. This physical system provides a striking illustration for the validity of the universal relaxation bound τ×T≥ħ/π in black-hole physics (here τ≡1/ℑω0 is the characteristic relaxation time of the composed black-hole-scalar-field system, and T is the Bekenstein–Hawking temperature of the black hole. In particular, it is shown that the relaxation dynamics of charged massive scalar fields in the charged Reissner–Nordström black-hole spacetime may saturate this quantum time-times-temperature inequality. Interestingly, we prove that potential violations of the bound by light scalar fields are excluded by the Schwinger-type pair-production mechanism (a vacuum polarization effect, a quantum phenomenon which restricts the physical parameters of the composed black-hole-charged-field system to the regime qQ≪M2μ2/ħ.
Charged Black Holes with Scalar Hair
Fan, Zhong-Ying
2015-01-01
We consider a class of Einstein-Maxwell-Dilaton theories, in which the dilaton coupling to the Maxwell field is not the usual single exponential function, but one with a stationary point. The theories admit two charged black holes: one is the Reissner-Nordstr\\o m (RN) black hole and the other has a varying dilaton. For a given charge, the new black hole in the extremal limit has the same AdS$_2\\times$Sphere near-horizon geometry as the RN black hole, but it carries larger mass. We then introduce some scalar potentials and obtain exact charged AdS black holes. We also generalize the results to black $p$-branes with scalar hair.
Energy Technology Data Exchange (ETDEWEB)
Blaga, Robert, E-mail: robert.blaga90@e-uvt.ro [Faculty of Physics, West University of Timişoara V. Pârvan Ave. 4, RO-300223 Timişoara (Romania)
2015-12-07
We investigate the energy radiated by an inertial scalar charge evolving in the expanding Poincaré patch of de Sitter spacetime, in the framework of scalar QED perturbation theory. We approximate the transition amplitude in the small expansion parameter limit and show that the leading contribution to the radiated energy has the form of the energy radiated by an accelerated particle in Minkowski space.
Dowker, J. S.
2016-04-01
I compute the conformal weights of the twist operators of free scalar fields for charged Rényi entropy in both odd and even dimensions. Explicit expressions can be found, in odd dimensions as a function of the chemical potential in the absence of a conical singularity and thence by images for all integer coverings. This method, developed some time ago, is equivalent, in results, to the replica technique. A review is given. The same method applies for even dimensions but a general form is more immediately available. For no chemical potential, the closed form in the covering order is written in an alternative way related to old trigonometric sums. Some derivatives are obtained. An analytical proof is given of a conjecture made by Bueno, Myers and Witczak-Krempa regarding the relation between the conformal weights and a corner coefficient (a universal quantity) in the Rényi entropy.
Conformal scalar field wormholes
Halliwell, Jonathan J.; Laflamme, Raymond
1989-01-01
The Euclidian Einstein equations with a cosmological constant and a conformally coupled scalar field are solved, taking the metric to be of the Robertson-Walker type. In the case Lambda = 0, solutions are found which represent a wormhole connecting two asymptotically flat Euclidian regions. In the case Lambda greater than 0, the solutions represent tunneling from a small Tolman-like universe to a large Robertson-Walker universe.
Tachyonic field interacting with Scalar (Phantom) Field
Chattopadhyay, Surajit; Debnath, Ujjal
2009-01-01
In this letter, we have considered the universe is filled with the mixture of tachyonic field and scalar or phantom field. If the tachyonic field interacts with scalar or phantom field, the interaction term decays with time and the energy for scalar field is transferred to tachyonic field or the energy for phantom field is transferred to tachyonic field. The tachyonic field and scalar field potentials always decrease, but phantom field potential always increases.
Structure Scalars for Charged Cylindrically Symmetric Relativistic Fluids
Sharif, M
2012-01-01
We investigate some structure scalars developed through Riemann tensor for self-gravitating cylindrically symmetric charged dissipative anisotropic fluid. We show that these scalars are directly related to the fundamental properties of the fluid. We formulate dynamical-transport equation as well as the mass function by including charge which are then expressed in terms of structure scalars. The effects of electric charge are investigated in the structure and evolution of compact objects. Finally, we show that all possible solutions of the field equations can be written in terms of these scalars.
Stability of gravitating charged-scalar solitons in a cavity
Ponglertsakul, Supakchai; Dolan, Sam R
2016-01-01
We present new regular solutions of Einstein-charged scalar field theory in a cavity. The system is enclosed inside a reflecting mirror-like boundary, on which the scalar field vanishes. The mirror is placed at the zero of the scalar field closest to the origin, and inside this boundary our solutions are regular. We study the stability of these solitons under linear, spherically symmetric perturbations of the metric, scalar and electromagnetic fields. If the radius of the mirror is sufficiently large, we present numerical evidence for the stability of the solitons. For small mirror radius, some of the solitons are unstable. We discuss the physical interpretation of this instability.
Hod, Shahar
2015-01-01
The quasinormal resonance spectrum $\\{\\omega_n(\\mu,q,M,Q)\\}_{n=0}^{n=\\infty}$ of charged massive scalar fields in the charged Reissner-Nordstr\\"om black-hole spacetime is studied {\\it analytically} in the large-coupling regime $qQ\\gg M\\mu$ (here $\\{\\mu, q\\}$ are respectively the mass and charge coupling constant of the field, and $\\{M,Q\\}$ are respectively the mass and electric charge of the black hole). This physical system provides a striking illustration for the validity of the universal relaxation bound $\\tau \\times T \\geq \\hbar/\\pi$ in black-hole physics (here $\\tau\\equiv 1/\\Im\\omega_0$ is the characteristic relaxation time of the composed black-hole-scalar-field system, and $T$ is the Bekenstein-Hawking temperature of the black hole). In particular, it is shown that the relaxation dynamics of charged massive scalar fields in the charged Reissner-Nordstr\\"om black-hole spacetime may {\\it saturate} this quantum time-times-temperature inequality. Interestingly, we prove that potential violations of the bou...
Stability of a collapsed scalar field and cosmic censorship
International Nuclear Information System (INIS)
The static and asymptotically flat solution to the Einstein-massless-scalar model with spherical symmetry describes the spacetime with a naked singularity when it has a nonvanishing scalar charge. We show that such a solution is unstable against the spherical scalar monopole perturbation. This suggests the validity of the cosmic censorship hypothesis in the spherical collapse of the scalar field
Scalar clouds in charged stringy black hole-mirror system
International Nuclear Information System (INIS)
It was reported that massive scalar fields can form bound states around Kerr black holes (Herdeiro and Radu, Phys. Rev. Lett. 112:221101, 2014). These bound states are called scalar clouds; they have a real frequency ω = mΩH, where m is the azimuthal index and ΩH is the horizon angular velocity of Kerr black hole. In this paper, we study scalar clouds in a spherically symmetric background, i.e. charged stringy black holes, with the mirror-like boundary condition. These bound states satisfy the superradiant critical frequency condition ω = qΦH for a charged scalar field, where q is the charge of the scalar field, and ΦH is the horizon's electrostatic potential. We show that, for the specific set of black hole and scalar field parameters, the clouds are only possible for specific mirror locations rm. It is shown that analytical results of the mirror location rm for the clouds perfectly coincide with numerical results in the qQ << 1 regime. We also show that the scalar clouds are also possible when the mirror locations are close to the horizon. Finally, we provide an analytical calculation of the specific mirror locations rm for the scalar clouds in the qQ >> 1 regime. (orig.)
Ultrarelativistic boost with scalar field
Svítek, O.; Tahamtan, T.
2016-02-01
We present the ultrarelativistic boost of the general global monopole solution which is parametrized by mass and deficit solid angle. The problem is addressed from two different perspectives. In the first one the primary object for performing the boost is the metric tensor while in the second one the energy momentum tensor is used. Since the solution is sourced by a triplet of scalar fields that effectively vanish in the boosting limit we investigate the behavior of a scalar field in a simpler setup. Namely, we perform the boosting study of the spherically symmetric solution with a free scalar field given by Janis, Newman and Winicour. The scalar field is again vanishing in the limit pointing to a broader pattern of scalar field behaviour during an ultrarelativistic boost in highly symmetric situations.
Symmetry inheritance of scalar fields
Smolić, Ivica
2015-07-01
Matter fields do not necessarily have to share the symmetries with the spacetime they live in. When this happens, we speak of the symmetry inheritance of fields. In this paper we classify the obstructions of symmetry inheritance by the scalar fields, both real and complex, and look more closely at the special cases of stationary and axially symmetric spacetimes. Since the symmetry noninheritance is present in the scalar fields of boson stars and may enable the existence of the black hole scalar hair, our results narrow the possible classes of such solutions. Finally, we define and analyse the symmetry noninheritance contributions to the Komar mass and angular momentum of the black hole scalar hair.
Symmetry inheritance of scalar fields
Smolić, Ivica
2015-01-01
Matter fields don't necessarily have to share the symmetries with the spacetime they live in. When this happens, we speak of the symmetry inheritance of fields. In this paper we classify the obstructions of symmetry inheritance by the scalar fields, both real and complex, and look more closely at the special cases of stationary and axially symmetric spacetimes. Since the symmetry noninheritance is present in the scalar fields of boson stars and may enable the existence of the black hole scalar hair, our results narrow the possible classes of such solutions. Finally, we define and analyse the symmetry noninheritance contributions to Komar mass and angular momentum of the black hole scalar hair.
Spherically symmetric scalar field collapse
Indian Academy of Sciences (India)
Koyel Ganguly; Narayan Banerjee
2013-03-01
It is shown that a scalar field, minimally coupled to gravity, may have collapsing modes even when the energy condition is violated, that is, for ( + 3) < 0. This result may be useful in the investigation of the possible clustering of dark energy. All the examples dealt with have apparent horizons formed before the formation of singularity. The singularities formed are shell focussing in nature. The density of the scalar field distribution is seen to diverge at singularity. The Ricci scalar also diverges at the singularity. The interior spherically symmetric metric is matched with exterior Vaidya metric at the hypersurface and the appropriate junction conditions are obtained.
Electrically charged Kerr black holes with scalar hair
Delgado, Jorge F M; Radu, Eugen; Runarsson, Helgi
2016-01-01
We construct electrically charged Kerr black holes (BHs) with scalar hair. Firstly, we take an uncharged scalar field, interacting with the electromagnetic field only indirectly, via the background metric. The corresponding family of solutions, dubbed Kerr-Newman BHs with ungauged scalar hair, reduces to (a sub-family of) Kerr-Newman BHs in the limit of vanishing scalar hair and to uncharged rotating boson stars in the limit of vanishing horizon. It adds one extra parameter to the uncharged solutions: the total electric charge. This leading electromagnetic multipole moment is unaffected by the scalar hair and can be computed by using Gauss's law on any closed 2-surface surrounding (a spatial section of) the event horizon. By contrast, the first sub-leading electromagnetic multipole -- the magnetic dipole moment --, gets suppressed by the scalar hair, such that the gyromagnetic ratio is always smaller than the Kerr-Newman value ($g=2$). Secondly, we consider a gauged scalar field and obtain a family of Kerr-Ne...
Particles and scalar waves in noncommutative charged black hole spacetime
Bhar, Piyali; Rahaman, Farook; Biswas, Ritabrata(Indian Institute of Engineering Sceince and Technology Shibpur (Formerly, Bengal Engineering and Science University Shibpur), 711 013, Howrah, West Bengal, India); Mondal, U. F.
2015-01-01
In this paper we have discussed geodesics and the motion of test particle in the gravitational field of noncommutative charged black hole spacetime. The motion of massive and massless particle have been discussed seperately. A comparative study of noncommutative charged black hole and usual Reissner-Nordstrom black hole has been done. The study of effective potential has also been included. Finally, we have examined the scattering of scalar waves in noncommutative charged black hole spacetime.
Particles and Scalar Waves in Noncommutative Charged Black Hole Spacetime
Piyali, Bhar; Farook, Rahaman; Ritabrata, Biswas; U. F., Mondal
2015-07-01
In this paper we have discussed geodesics and the motion of test particle in the gravitational field of non-commutative charged black hole spacetime. The motion of massive and massless particle have been discussed seperately. A comparative study of noncommutative charged black hole and usual Reissner-Nordström black hole has been done. The study of effective potential has also been included. Finally, we have examined the scattering of scalar waves in noncommutative charged black hole spacetime.
Stationary scalar configurations around extremal charged black holes
Degollado, Juan Carlos
2013-01-01
We consider the minimally coupled Klein-Gordon equation for a charged, massive scalar field in the non-extremal Reissner-Nordstr\\"om background. Performing a frequency domain analysis, using a continued fraction method, we compute the frequencies \\omega for quasi-bound states. We observe that, as the extremal limit for both the background and the field is approached, the real part of the quasi-bound states frequencies $\\mathcal{R}(\\omega)$ tends to the mass of the field and the imaginary part $\\mathcal{I}(\\omega)$ tends to zero, for any angular momentum quantum number $\\ell$. The limiting frequencies in this double extremal limit are shown to correspond to a distribution of extremal scalar particles, at stationary positions, in no-force equilibrium configurations with the background. Thus, generically, these stationary scalar configurations are regular at the event horizon. If, on the other hand, the distribution contains scalar particles at the horizon, the configuration becomes irregular therein, in agreeme...
Charged scalar waves from the RN/CFT correspondence
Wu, Xing-Hua
2016-01-01
We examine new tests for (non-)extremal Reissner-Nordstr\\"om/Conformal field theory correspondences (RN/CFT) in this paper. The decay rate of the charged scalar wave sourced by an orbiting star around the black hole is computed and is compared with the decay rate computed in the corresponding CFT. We find that precise matches are achieved.
Discrete scalar fields and general relativity
De Souza, M M
2000-01-01
The physical meaning, the properties and the consequences of a discrete scalar field are discussed; limits for a continuous mathematical description of fundamental physics is a natural outcome of discrete fields with discrete interactions. The discrete scalar field is ultimately the gravitational field of general relativity, necessarily, and there is no place for any other fundamental scalar field, in this context.
International Nuclear Information System (INIS)
The generalized form of Killingbeck potential is an attractive Coulomb term plus a linear term and a harmonic oscillator term, i.e. −a/r + br + λr2, which has a useful application in quarkonium spectroscopy. The ground state energy with the corresponding wave function are obtained for any arbitrary m-state in two-dimensional Klein–Gordon equation with equal mixture of scalar–vector Killingbeck potentials in the presence of constant magnetic and singular Ahoronov–Bohm flux fields perpendicular to the plane where the interacting charged particle is confined. The analytical exact iteration method is used in our solution. We obtain the energy eigensolutions for particle and antiparticle corresponding to S(r) = V(r) and S(r) = −V(r) cases, respectively. Some special cases like the Coulomb, harmonic oscillator potentials and the nonrelativistic limits are found in presence and absence of external fields. (author)
The traversable wormhole with classical scalar fields
Kim, S. -W; Kim, S. P.
1999-01-01
We study the Lorentzian static traversable wormholes coupled to quadratic scalar fields. We also obtain the solutions of the scalar fields and matters in the wormhole background and find that the minimal size of the wormhole should be quantized under the appropriate boundary conditions for the positive non-minimal massive scalar field.
Scalar Fields in Particle Physics
Pedro, Leonardo
2016-01-01
Extending the scalar sector helps in studying the Higgs mechanism and some Standard Model problems. We implement the correspondence between the gauge-dependent elementary states and the non-perturbative non-abelian gauge-invariant asymptotic states, necessary to study the non-perturbative phenomenology of two-Higgs-doublet models. The Flavour and CP violation in experimental data follows a hierarchical pattern, accounted by the Standard Model. We define the Minimal Flavour Violation condition with six spurions in effective field theories, implying Flavour and CP violation entirely dependent on the fermion mixing matrices but independent of the fermion masses hierarchy; it is renormalization-group invariant. We study the phenomenology of renormalizable two-Higgs-doublet models which verify the defined condition as consequence of a symmetry; new light physical scalars, mediating Flavour Changing Neutral Currents, are allowed by flavour data without flavour coefficients beyond the Standard Model; we tested the m...
Entropic quantization of scalar fields
Energy Technology Data Exchange (ETDEWEB)
Ipek, Selman; Caticha, Ariel [Department of Physics, University at Albany-SUNY, Albany, NY 12222 (United States)
2015-01-13
Entropic Dynamics is an information-based framework that seeks to derive the laws of physics as an application of the methods of entropic inference. The dynamics is derived by maximizing an entropy subject to constraints that represent the physically relevant information that the motion is continuous and non-dissipative. Here we focus on the quantum theory of scalar fields. We provide an entropic derivation of Hamiltonian dynamics and using concepts from information geometry derive the standard quantum field theory in the Schrödinger representation.
Entropic quantization of scalar fields
Ipek, Selman; Caticha, Ariel
2015-01-01
Entropic Dynamics is an information-based framework that seeks to derive the laws of physics as an application of the methods of entropic inference. The dynamics is derived by maximizing an entropy subject to constraints that represent the physically relevant information that the motion is continuous and non-dissipative. Here we focus on the quantum theory of scalar fields. We provide an entropic derivation of Hamiltonian dynamics and using concepts from information geometry derive the standard quantum field theory in the Schrödinger representation.
Gravitational Frames and Scalar Field Dynamics
Ozaydin, M T
2016-01-01
Scalar fields describe interesting phenomena such as Higgs bosons, dark matter and dark energy, and are found to be quite common in physical theories. These fields are susceptible to gravitational forces so that being massless is not enough to remain conformal invariant. They should also be connected directly to the scalar curvature. Because of this characteristics, we investigated the structure and interactions of scalar fields under the conformal transformations. We show how to reduce the quadratic quantum contributions in the single scalar field theory. In the multi-scalar field theories, we analyzed interactions in certain limits. We suggest a new method for stabilizing Higgs bosons.
Scalar Field (Wave) Dark Matter
Matos, T
2016-01-01
Recent high-quality observations of dwarf and low surface brightness (LSB) galaxies have shown that their dark matter (DM) halos prefer flat central density profiles. On the other hand the standard cold dark matter model simulations predict a more cuspy behavior. Feedback from star formation has been widely used to reconcile simulations with observations, this might be successful in field dwarf galaxies but its success in low mass galaxies remains uncertain. One model that have received much attention is the scalar field dark matter model. Here the dark matter is a self-interacting ultra light scalar field that forms a cosmological Bose-Einstein condensate, a mass of $10^{-22}$eV/c$^2$ is consistent with flat density profiles in the centers of dwarf spheroidal galaxies, reduces the abundance of small halos, might account for the rotation curves even to large radii in spiral galaxies and has an early galaxy formation. The next generation of telescopes will provide better constraints to the model that will help...
Charged Scalar-Tensor Boson Stars Equilibrium, Stability and Evolution
Whinnett, A W
1999-01-01
We study charged boson stars in scalar-tensor (ST) gravitational theories. We analyse the weak field limit of the solutions and analytically show that there is a maximum charge to mass ratio for the bosons above which the weak field solutions are not stable. This charge limit can be greater than the GR limit for a wide class of ST theories. We numerically investigate strong field solutions in both the Brans Dicke and power law ST theories. We find that the charge limit decreases with increasing central boson density. We discuss the gravitational evolution of charged and uncharged boson stars in a cosmological setting and show how, at any point in its evolution, the physical properties of the star may be calculated by a rescaling of a solution whose asymptotic value of the scalar field is equal to its initial asymptotic value. We focus on evolution in which the particle number of the star is conserved and we find that the energy and central density of the star decreases as the cosmological time increases. We a...
Induced vacuum polarization of scalar field by impenetrable magnetic tube
Gorkavenko, V M; Stepanov, O B
2009-01-01
We investigated the influence of external magnetic field in the tube on the vacuum of massive charged scalar field for the case of arbitrary space-time dimension. The tube is considered impenetrable for scalar field and obeys Dirichlet boundary condition on bounding surface. It was shown that for particular case of 2+1 dimensional space-time the induced vacuum energy of scalar field outside the tube can be numerically calculated without regularization procedure. The dependencies of the induced vacuum energy upon distance from the tube under the different values of transversal radius of it were obtained.
Bulk scalar field in DGP braneworld cosmology
Ansari, Rizwan ul Haq
2007-01-01
We investigated the effects of bulk scalar field in the braneworld cosmological scenario. The Friedmann equations and acceleration condition in presence of the bulk scalar field for a zero tension brane and cosmological constant are studied. In DGP model the effective Einstein equation on the brane is obtained with bulk scalar field. The rescaled bulk scalar field on the brane in the DGP model behaves as an effective four dimensional field, thus standard type cosmology is recovered. In present study of the DGP model, the late-time accelerating phase of the universe can be explained .
Gravitational Frames and Scalar Field Dynamics
Ozaydin, M. T.; Pirinccioglu, N.
2016-01-01
Scalar fields describe interesting phenomena such as Higgs bosons, dark matter and dark energy, and are found to be quite common in physical theories. These fields are susceptible to gravitational forces so that being massless is not enough to remain conformal invariant. They should also be connected directly to the scalar curvature. Because of this characteristics, we investigated the structure and interactions of scalar fields under the conformal transformations. We show how to reduce the q...
Maeda, Hideki
2016-01-01
We present a simple and complete classification of static solutions in the Einstein-Maxwell system with a massless scalar field in arbitrary $n(\\ge 3)$ dimensions. We consider spacetimes which correspond to a warped product $M^2 \\times K^{n-2}$, where $K^{n-2}$ is a $(n-2)$-dimensional Einstein space. The scalar field is assumed to depend only on the radial coordinate and the electromagnetic field is purely electric. The general solution with a non-constant real scalar field consists of seven solutions for $n\\ge 4$ and three solutions for $n=3$. None of them is endowed of a Killing horizon in accordance with the no-hair theorem.
Late-Time Evolution of Charged Gravitational Collapse and Decay of Charged Scalar Hair, 2
Hod, S; Hod, Shahar; Piran, Tsvi
1998-01-01
We study analytically the initial value problem for a charged massless scalar-field on a Reissner-Nordström spacetime. Using the technique of spectral decomposition we extend recent results on this problem. Following the no-hair theorem we reveal the dynamical physical mechanism by which the charged hair is radiated away. We show that the charged perturbations decay according to an inverse power-law behaviour at future timelike infinity and along future null infinity. Along the future outer horizon we find an oscillatory inverse power-law relaxation of the charged fields. We find that a charged black hole becomes ``bald'' slower than a neutral one, due to the existence of charged perturbations. Our results are also important to the study of mass-inflation and the stability of Cauchy horizons during a dynamical gravitational collapse of charged matter in which a charged black-hole is formed.
Scalar field mass in generalized gravity
Faraoni, Valerio
2009-01-01
The notions of mass and range of a Brans-Dicke-like scalar field in scalar-tensor and f(R) gravity are subject to an ambiguity that hides a potential trap. We spell out this ambiguity and identify a physically meaningful and practical definition for these quantities. This is relevant when giving a mass to this scalar in order to circumvent experimental limits on the PPN parameters coming from Solar System experiments.
Primordial fluctuations without scalar fields
Magueijo, J
2009-01-01
We revisit the question of whether fluctuations in hydrodynamical, adiabatical matter could explain the observed structures in our Universe. We consider matter with variable equation of state $w=p_0/\\ep_0$ and a concomitant (under the adiabatic assumption) density dependent speed of sound, $c_s$. We find a limited range of possibilities for a set up when modes start inside the Hubble radius, then leaving it and freezing out. For expanding Universes, power-law $w(\\ep_0)$ models are ruled out (except when $c_s^2\\propto w \\ll 1$, requiring post-stretching the seeded fluctuations); but sharper profiles in $c_s$ do solve the horizon problem. Among these, a phase transition in $c_s$ is notable for leading to scale-invariant fluctuations if the initial conditions are thermal. For contracting Universes all power-law $w(\\ep_0)$ solve the horizon problem, but only one leads to scale-invariance: $w\\propto \\ep_0^2$ and $c_s\\propto \\ep_0$. This model bypasses a number of problems with single scalar field cyclic models (fo...
Scalar field radiation from dilatonic black holes
Gohar, H.; Saifullah, K.
2012-12-01
We study radiation of scalar particles from charged dilaton black holes. The Hamilton-Jacobi method has been used to work out the tunneling probability of outgoing particles from the event horizon of dilaton black holes. For this purpose we use WKB approximation to solve the charged Klein-Gordon equation. The procedure gives Hawking temperature for these black holes as well.
Multiple critical gravitational collapse of charged scalar with reflecting wall
Cai, Rong-Gen
2016-01-01
In this paper, we present the results on the gravitational collapse of charged massless scalar field in asymptotically flat spacetime with a perfectly reflecting wall. Differing from previous works, we study the system in the double null coordinates, by which we could simulate the system until the black hole forms with higher precision but less performance time. We investigate the influence of charge on the black hole formation and the scaling behavior near the critical collapses. The gapless and gapped critical behaviors for black hole mass and charge are studied numerically. We find that they satisfy the scaling laws for critical gravitational collapse but the gapped critical behavior is different from its AdS counterpart.
Static scalar field solutions in symmetric gravity
Hossenfelder, S.
2016-09-01
We study an extension of general relativity with a second metric and an exchange symmetry between the two metrics. Such an extension might help to address some of the outstanding problems with general relativity, for example the smallness of the cosmological constant. We here derive a family of exact solutions for this theory. In this two-parameter family of solutions the gravitational field is sourced by a time-independent massless scalar field. We find that the only limit in which the scalar field entirely vanishes is flat space. The regular Schwarzschild-solution is left with a scalar field hidden in the second metric’s sector.
Charged scalar perturbations around Garfinkle–Horowitz–Strominger black holes
Directory of Open Access Journals (Sweden)
Cheng-Yong Zhang
2015-10-01
Full Text Available We examine the stability of the Garfinkle–Horowitz–Strominger (GHS black hole under charged scalar perturbations. Employing the appropriate numerical methods, we show that the GHS black hole is always stable against charged scalar perturbations. This is different from the results obtained in the de Sitter and anti-de Sitter black holes. Furthermore, we argue that in the GHS black hole background there is no amplification of the incident charged scalar wave to cause the superradiance, so that the superradiant instability cannot exist in this spacetime.
Gravitational Field Shielding by Scalar Field and Type II Superconductors
Zhang B. J.; Zhang T. X.; Guggilia P.; Dohkanian M.
2013-01-01
The gravitational field shielding by scalar field and type II superconductors are theoret- ically investigated. In accord with the well-developed five-dimensional fully covariant Kaluza-Klein theory with a scalar field, which unifies the Einsteinian general relativity and Maxwellian electromagnetic theory, the scalar field cannot only polarize the space as shown previously, but also flatten the space as indicated recently. The polariza- tion of space decreases the...
Discrete scalar field and general relativity
De Souza, M M
2001-01-01
What is the nature - continuous or discrete - of matter and of its fundamental interactions? The physical meaning, the properties and the consequences of a discrete scalar field are discussed; limits for the validity of a mathematical description of fundamental physics in terms of continuum fields are a natural outcome of discrete fields with discrete interactions. Two demarcating points (a near and a far) define a domain where no difference between the discrete and the standard continuum field formalisms can be experimentally detected. Discrepancies, however, can be observed as a continuous-interaction is always stronger below the near point and weaker above the far point than a discrete one. The connections between the discrete scalar field and gravity from general relativity are discussed. Whereas vacuum solutions of general relativity can be retrieved from discrete scalar field solutions, this cannot be extended to solutions in presence of massive sources as they require a true tensor metric field. Contac...
Gravitational Gauge Interactions of Scalar Field
Institute of Scientific and Technical Information of China (English)
WUNing
2003-01-01
Quantum gauge theory of gravity is formulated based on gauge principle. Because the Lagrangian has strict local gravitational gauge symmetry, gravitational gauge theory is a perturbatively renormalizable quantum theory. Gravitational gauge interactions of scalar field are studied in this paper. In quantum gauge theory of gravity, scalar field minimal couples to gravitational field through gravitational gauge covariant derivative. Comparing the Lagrangian for scalar field in quantum gauge theory of gravity with the corresponding Lagrangian in quantum fields in curved space-time, the definition for metric in curved space-time in geometry picture of gravity can be obtained, which is expressed by gravitational gauge field. In classical level, the Lagrangian and Hamiltonian approaches are also discussed.
Gravitational Field Shielding by Scalar Field and Type II Superconductors
Directory of Open Access Journals (Sweden)
Zhang B. J.
2013-01-01
Full Text Available The gravitational field shielding by scalar field and type II superconductors are theoret- ically investigated. In accord with the well-developed five-dimensional fully covariant Kaluza-Klein theory with a scalar field, which unifies the Einsteinian general relativity and Maxwellian electromagnetic theory, the scalar field cannot only polarize the space as shown previously, but also flatten the space as indicated recently. The polariza- tion of space decreases the electromagnetic field by increasing the equivalent vacuum permittivity constant, while the flattening of space decreases the gravitational field by decreasing the equivalent gravitational constant. In other words, the scalar field can be also employed to shield the gravitational field. A strong scalar field significantly shield the gravitational field by largely decreasing the equivalent gravitational constant. According to the theory of gravitational field shielding by scalar field, the weight loss experimentally detected for a sample near a rotating ceramic disk at very low tempera- ture can be explained as the shielding of the Earth gravitational field by the Ginzburg- Landau scalar field, which is produced by the type II superconductors. The significant shielding of gravitational field by scalar field produced by superconductors may lead to a new spaceflight technology in future.
Chaotic instantons in scalar field theory
Addazi, Andrea
2016-01-01
We consider a new class of instantons in context of quantum field theory of a scalar field coupled with a chaotic background source field. We show how the instanton associated to the quantum tunneling from a metastable false to the true vacuum will be corrected by an exponential enhancement factor. Possible implications are discussed.
A scalar field dark energy model: Noether symmetry approach
Dutta, Sourav; Panja, Madan Mohan; Chakraborty, Subenoy
2016-04-01
Scalar field dark energy cosmology has been investigated in the present paper in the frame work of Einstein gravity. In the context of Friedmann-Lemaitre-Robertson-Walker space time minimally coupled scalar field with self interacting potential and non-interacting perfect fluid with barotropic equation of state (dark matter) is chosen as the matter context. By imposing Noether symmetry on the Lagrangian of the system the symmetry vector is obtained and the self interacting potential for the scalar field is determined. Then we choose a point transformation (a, φ )→ (u, v) such that one of the transformation variable (say u) is cyclic for the Lagrangian. Subsequently, using conserved charge (corresponding to the cyclic co-ordinate) and the constant of motion, solutions are obtained. Finally, the cosmological implication of the solutions in the perspective of recent observation has been examined.
Topological charge conservation in stochastic optical fields
Roux, Filippus S.
2016-05-01
The fact that phase singularities in scalar stochastic optical fields are topologically conserved implies the existence of an associated conserved current, which can be expressed in terms of local correlation functions of the optical field and its transverse derivatives. Here, we derive the topological charge current for scalar stochastic optical fields and show that it obeys a conservation equation. We use the expression for the topological charge current to investigate the topological charge flow in inhomogeneous stochastic optical fields with a one-dimensional topological charge density.
Intermediate inflation driven by DBI scalar field
Nazavari, N.; Mohammadi, A.; Ossoulian, Z.; Saaidi, Kh.
2016-06-01
Picking out a DBI scalar field as inflation, the slow-rolling inflationary scenario is studied by attributing an exponential time function to scale factor, known as intermediate inflation. The perturbation parameters of the model are estimated numerically for two different cases, and the final result is compared with Planck data. The diagram of tensor-to-scalar ratio r versus scalar spectra index ns is illustrated, and it is found that they are within an acceptable range as suggested by Planck. In addition, the acquired values for amplitude of scalar perturbation reveal the ability of the model to depict a good picture of the Universe in one of its earliest stages. As a further argument, the non-Gaussianity is investigated, displaying that the model prediction stands in a 68% C.L. regime according to the latest Planck data.
Cosmological Constraints on Scalar Field Dark Matter
Jesus, J F; Pereira, S H
2015-01-01
In this paper we study a real scalar field as a possible candidate to explain the dark matter in the universe. In the context of a free scalar field with quadratic potential, we have used observational $H(z)$ data to constrain the dark matter mass to $m=\\left(3.46^{+0.38+0.75+1.1}_{-0.43-0.92-1.5}\\right)\\times10^{-33}$ eV. This value is much below some previous estimates of $m\\sim 10^{-22}$ eV found in some models, which we explain as being due to a slightly different formulation, but in complete agreement with a recent model based on a cosmological scalar field harmonic oscillator, for which $m\\sim 10^{-32}$ eV. Although scalar field dark matter (SFDM) is much disfavored, as it gives rise to ultra hot dark matter and could halt structure formation, different scalar field potentials could alleviate this issue.
Gravitational waves from scalar field accretion
Núnez, Darío; Degollado, Juan Carlos; Moreno, Claudia
2011-01-01
Our aim in this work is to outline some physical consequences of the interaction between black holes and scalar field halos in terms of gravitational waves. In doing so, the black hole is taken as a static and spherically symmetric gravitational source, {\\it i. e.} the Schwarzschild black hole, and we work within the test field approximation, considering that the scalar field lives in the curved space-time outside the black hole. We focused on the emission of gravitational waves when the blac...
Cosmological twinlike models with multi scalar fields
Zhong, Yuan; Liu, Yu-Xiao
2016-01-01
We consider cosmological models driven by several canonical or noncanonical scalar fields. We show how the superpotential method enables one to construct twinlike models for a particular canonical model from some noncanonical ones. We conclude that it is possible to construct twinlike models for multi-field cosmological models, even when the spatial curvature is nonzero. This work extends the discussions of [D. Bazeia and J. D. Dantas, Phys. Rev. D, 85 (2012) 067303] to cases with multi scalar fields and with non-vanished spatial curvature, by using a different superpotential method.
Exact solutions for the biadjoint scalar field
White, Chris D
2016-01-01
Biadjoint scalar theories are novel field theories that arise in the study of non-abelian gauge and gravity amplitudes. In this short paper, we present exact nonperturbative solutions of the field equations, and compare their properties with monopole-like solutions in non-abelian gauge theory. Our results may pave the way for nonperturbative studies of the double copy.
Gravitational peculiarities of a scalar field
International Nuclear Information System (INIS)
The zero-adjoint of a time-static Ricci-flat solution to Einstein's field equations is investigated. It represents a spacetime curved solely by a massless scalar field. The cylindrical symmetry is assumed to permit both planar and non-planar geodetic motions. Unusual, velocity-dependent gravitational features are encountered from these geodesics. (Author)
D-BIonic Screening of Scalar Fields
Burrage, Clare
2014-01-01
We study a new screening mechanism which is present in Dirac-Born-Infeld (DBI)-like theories. A scalar field with a DBI-like Lagrangian is minimally coupled to matter. In the vicinity of sufficiently dense sources, non-linearities in the scalar dominate and result in an approximately constant acceleration on a test particle, thereby suppressing the scalar force relative to gravity. Unlike generic P(X) theories, screening happens within the regime of validity of the effective field theory, thanks to the DBI symmetry. This symmetry also allows the removal of a constant field gradient, like in galileons. Not surprisingly, perturbations around the spherically-symmetry background propagate superluminally, but we argue for a chronology protection analogous to galileons. We derive constraints on the theory parameters from tests of gravity and discuss various extensions.
Fluid/Gravity Correspondence with Scalar Field and Electromagnetic Field
Chou, Chia-Jui; Yang, Yi; Yuan, Pei-Hung
2016-01-01
We consider fluid/gravity correspondence in a general rotating black hole background with scalar and electromagnetic fields. Using the method of Petrov-like boundary condition, we show that the scalar and the electromagnetic fields contribute external forces to the dual Navier-Stokes equation and the rotation of black hole induces the Coriolis force.
Generalized gravitational entropy of interacting scalar field and Maxwell field
Directory of Open Access Journals (Sweden)
Wung-Hong Huang
2014-12-01
Full Text Available The generalized gravitational entropy proposed recently by Lewkowycz and Maldacena is extended to the interacting real scalar field and Maxwell field system. Using the BTZ geometry we first investigate the case of free real scalar field and then show a possible way to calculate the entropy of the interacting scalar field. Next, we investigate the Maxwell field system. We exactly solve the wave equation and calculate the analytic value of the generalized gravitational entropy. We also use the Einstein equation to find the effect of backreaction of the Maxwell field on the area of horizon. The associated modified area law is consistent with the generalized gravitational entropy.
Generalized gravitational entropy of interacting scalar field and Maxwell field
Huang, Wung-Hong
2014-12-01
The generalized gravitational entropy proposed recently by Lewkowycz and Maldacena is extended to the interacting real scalar field and Maxwell field system. Using the BTZ geometry we first investigate the case of free real scalar field and then show a possible way to calculate the entropy of the interacting scalar field. Next, we investigate the Maxwell field system. We exactly solve the wave equation and calculate the analytic value of the generalized gravitational entropy. We also use the Einstein equation to find the effect of backreaction of the Maxwell field on the area of horizon. The associated modified area law is consistent with the generalized gravitational entropy.
Generalized gravitational entropy of interacting scalar field and Maxwell field
Energy Technology Data Exchange (ETDEWEB)
Huang, Wung-Hong, E-mail: whhwung@mail.ncku.edu.tw
2014-12-12
The generalized gravitational entropy proposed recently by Lewkowycz and Maldacena is extended to the interacting real scalar field and Maxwell field system. Using the BTZ geometry we first investigate the case of free real scalar field and then show a possible way to calculate the entropy of the interacting scalar field. Next, we investigate the Maxwell field system. We exactly solve the wave equation and calculate the analytic value of the generalized gravitational entropy. We also use the Einstein equation to find the effect of backreaction of the Maxwell field on the area of horizon. The associated modified area law is consistent with the generalized gravitational entropy.
Age Crises, Scalar Fields, and the Apocalypse
Jackson, J. C.
Recent observations suggest that Hubble's constant is large, to the extent that the oldest stars appear to have ages which are greater than the Hubble time, and that the Hubble expansion is slowing down, so that according to conventional cosmology the age of the Universe is less than the Hubble time. The concepts of weak and strong age crises (respectively t01/H0 and q0>0) are introduced. These observations are reconciled in models which are dynamically dominated by a homogeneous scalar field, corresponding to an ultra-light boson whose Compton wavelength is of the same order as the Hubble radius. Two such models are considered, an open one with vacuum energy comprising a conventional cosmological term and a scalar field component, and a flat one with a scalar component only, aimed respectively at weak and strong age crises. Both models suggest that anti-gravity plays a significant role in the evolution of the Universe.
Gravitational waves from scalar field accretion
Núnez, Darío; Moreno, Claudia
2011-01-01
Our aim in this work is to outline some physical consequences of the interaction between black holes and scalar field halos in terms of gravitational waves. In doing so, the black hole is taken as a static and spherically symmetric gravitational source, {\\it i. e.} the Schwarzschild black hole, and we work within the test field approximation, considering that the scalar field lives in the curved space-time outside the black hole. We focused on the emission of gravitational waves when the black hole is perturbed by the surrounding scalar field matter. The symmetries of the spacetime and the simplicity of the matter source allow, by means of a spherical harmonic decomposition, to study the problem by means of a one dimensional description. Some properties of such gravitational waves are discussed as a function of the parameters of the infalling scalar field, and allow us to make the conjecture that the gravitational waves carry information on the type of matter that generated them.
Cosmological evolution of a ghost scalar field
Sushkov, S. V.; Kim, S. -W
2004-01-01
We consider a scalar field with a negative kinetic term minimally coupled to gravity. We obtain an exact non-static spherically symmetric solution which describes a wormhole in cosmological setting. The wormhole is shown to connect two homogeneous spatially flat universes expanding with acceleration. Depending on the wormhole's mass parameter $m$ the acceleration can be constant (the de Sitter case) or infinitely growing.
Gravitational Gauge Interactions of Scalar Field
Institute of Scientific and Technical Information of China (English)
WU Ning
2003-01-01
Quantum gauge theory of gravity is formulated based on gauge principle. Because the Lagrangian hasstrict local gravitational gauge symmetry, gravitational gauge theory is a perturbatively renormalizable quantum theory.Gravitational gauge interactions of scalar field are studied in this paper. In quantum gauge theory of gravity, scalar fieldminimal couples to gravitational field through gravitational gauge covariant derivative. Comparing the Lagrangian forscalar field in quantum gauge theory of gravity with the corresponding Lagrangian in quantum fields in curved space-time, the definition for metric in curved space-time in geometry picture of gravity can be obtained, which is expressedby gravitational gauge field. In classical level, the Lagrangian and Hamiltonian approaches are also discussed.
Black hole with a scalar field as a particle accelerator
Zaslavskii, O B
2016-01-01
We consider black holes with the background scalar field and test particles that can interact with this field directly. Then, particle collision near a black hole can lead to unbound energy $E_{c.m.}$ in the centre of mass frame (contrary to some recent claims in literature). This happens if one of particles is neutral whereas another one has nonzero scalar charge. Kinematically, two cases occur here. (i) A neutral particle approaches the horizon with the speed of light while the velocity of the charged one remains separated from it (this is direct analogue of the situation with collision of geodesic particles.). (ii) Both particles approach the horizon with the speed almost equal to that of light but with different rates. As a result, in both cases the relative velocity also approaches the speed of light, so that $E_{c.m.}$ $\\ $becomes unbound.
Two scalar field cosmology from coupled one-field models
Moraes, P H R S
2014-01-01
One possible description for the current accelerated expansion of the universe is quintessence dynamics. The basic idea of quintessence consists of analyzing cosmological scenarios driven by scalar fields. In this work we present some interesting features on the cosmological scenario obtained from the solutions of an effective two scalar field model in a flat space-time. This effective model was constructed by coupling two single scalar field systems in a nontrivial way via an extension method. The solutions related to the fields allowed us to compute analytical cosmological parameters. The behavior of these parameters are highlighted, as well as the different epochs obtained from them.
Slowly rotating neutron stars in scalar-tensor theories with a massive scalar field
Yazadjiev, Stoytcho S.; Doneva, Daniela D.; Popchev, Dimitar
2016-04-01
In the scalar-tensor theories with a massive scalar field, the coupling constants, and the coupling functions in general, which are observationally allowed, can differ significantly from those in the massless case. This fact naturally implies that the scalar-tensor neutron stars with a massive scalar field can have rather different structure and properties in comparison with their counterparts in the massless case and in general relativity. In the present paper, we study slowly rotating neutron stars in scalar-tensor theories with a massive gravitational scalar. Two examples of scalar-tensor theories are examined—the first example is the massive Brans-Dicke theory and the second one is a massive scalar-tensor theory indistinguishable from general relativity in the weak-field limit. In the latter case, we study the effect of the scalar field mass on the spontaneous scalarization of neutron stars. Our numerical results show that the inclusion of a mass term for the scalar field indeed changes the picture drastically compared to the massless case. It turns out that mass, radius, and moment of inertia for neutron stars in massive scalar-tensor theories can differ drastically from the pure general relativistic solutions if sufficiently large masses of the scalar field are considered.
Dynamical analysis in scalar field cosmology
Paliathanasis, Andronikos; Basilakos, Spyros; Barrow, John D
2015-01-01
A general method to extract exact cosmological solutions for scalar field dark energy in the presence of perfect fluids is presented. We use as a selection rule the existence of invariant transformations for the Wheeler De Witt (WdW) equation. We show that the existence of point transformation in which the WdW equation is invariant is equivalent to the existence of conservation laws for the field equations. Mathematically, the existence of extra integrals of motion indicates the existence of analytical solutions. We extend previous work by providing exact solutions for the Hubble parameter and the effective dark energy equation of state parameter for cosmologies containing a combination of perfect fluid and a scalar field whose self-interaction potential is a power of hyperbolic functions. Finally, we perform a dynamical analysis by studying the fixed points of the field equations using dimensionless variables. Amongst the variety of dynamical cases, we find that if the current cosmological model is Liouville...
Dissipation element analysis of turbulent scalar fields
Energy Technology Data Exchange (ETDEWEB)
Wang Lipo; Peters, Norbert [Institut fuer Technische Verbrennung, RWTH-Aachen, 52056 Aachen (Germany)], E-mail: wang@itv.rwth-aachen.de, E-mail: n.peters@itv.rwth-aachen.de
2008-12-15
Dissipation element analysis is a new approach for studying turbulent scalar fields. Gradient trajectories starting from each material point in a scalar field {phi}'(x-vector,t) in ascending directions will inevitably reach a maximal and a minimal point. The ensemble of material points sharing the same pair ending points is named a dissipation element. Dissipation elements can be parameterized by the length scale l and the scalar difference {delta}{phi} ', which are defined as the straight line connecting the two extremal points and the scalar difference at these points, respectively. The decomposition of a turbulent field into dissipation elements is space-filling. This allows us to reconstruct certain statistical quantities of fine scale turbulence which cannot be obtained otherwise. The marginal probability density function (PDF) of the length scale distribution based on a Poisson random cutting-reconnection process shows satisfactory agreement with the direct numerical simulation (DNS) results. In order to obtain the further information that is needed for the modeling of scalar mixing in turbulence, such as the marginal PDF of the length of elements and all conditional moments as well as their scaling exponents, there is a need to model the joint PDF of l and {delta}{phi} ' as well. A compensation-defect model is put forward in this work to show the dependence of {delta}{phi} ' on l. The agreement between the model prediction and DNS results is satisfactory, which may provide another explanation of the Kolmogorov scaling and help to improve turbulent mixing models. Furthermore, intermittency and cliff structure can also be related to and explained from the joint PDF.
Entanglement entropy for free scalar fields in AdS
Sugishita, Sotaro
2016-01-01
We compute entanglement entropy for free massive scalar fields in anti-de Sitter (AdS) space. The entangling surface is a minimal surface whose boundary is a sphere at the boundary of AdS. The entropy can be evaluated from the thermal free energy of the fields on a topological black hole by using the replica method. In odd-dimensional AdS, exact expressions of the Renyi entropy S_n are obtained for arbitrary n. We also evaluate 1-loop corrections coming from the scalar fields to holographic entanglement entropy. Applying the results, we compute the leading difference of entanglement entropy between two holographic CFTs related by a renormalization group flow triggered by a double trace deformation. The difference is proportional to the shift of a central charge under the flow.
Euclidean wormholes with minimally coupled scalar fields
International Nuclear Information System (INIS)
A detailed study of quantum and semiclassical Euclidean wormholes for Einstein's theory with a minimally coupled scalar field has been performed for a class of potentials. Massless, constant, massive (quadratic in the scalar field) and inverse (linear) potentials admit the Hawking and Page wormhole boundary condition both in the classically forbidden and allowed regions. An inverse quartic potential has been found to exhibit a semiclassical wormhole configuration. Classical wormholes under a suitable back-reaction leading to a finite radius of the throat, where the strong energy condition is satisfied, have been found for the zero, constant, quadratic and exponential potentials. Treating such classical Euclidean wormholes as an initial condition, a late stage of cosmological evolution has been found to remain unaltered from standard Friedmann cosmology, except for the constant potential which under the back-reaction produces a term like a negative cosmological constant. (paper)
Scalar Field Quantum Inequalities in Static Spacetimes
Pfenning, Michael J.; Ford, L. H.
1997-01-01
We discuss quantum inequalities for minimally coupled scalar fields in static spacetimes. These are inequalities which place limits on the magnitude and duration of negative energy densities. We derive a general expression for the quantum inequality for a static observer in terms of a Euclidean two-point function. In a short sampling time limit, the quantum inequality can be written as the flat space form plus subdominant correction terms dependent upon the geometric properties of the spaceti...
Reconstructing bidimensional scalar field theory models
Energy Technology Data Exchange (ETDEWEB)
Flores, Gabriel H.; Svaiter, N.F. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)]. E-mail: gflores@cbpf.br; nfuxsvai@cbpf.br
2001-07-01
In this paper we review how to reconstruct scalar field theories in two dimensional spacetime starting from solvable Scrodinger equations. Theree different Schrodinger potentials are analyzed. We obtained two new models starting from the Morse and Scarf II hyperbolic potencials, the U ({theta}) {theta}{sup 2} In{sup 2} ({theta}{sup 2}) model and U ({theta}) = {theta}{sup 2} cos{sup 2} (In({theta}{sup 2})) model respectively. (author)
a Nonassociative Quaternion Scalar Field Theory
Giardino, Sergio; Teotônio-Sobrinho, Paulo
2013-10-01
A nonassociative Groenewold-Moyal (GM) plane is constructed using quaternion-valued function algebras. The symmetrized multiparticle states, the scalar product, the annihilation/creation algebra and the formulation in terms of a Hopf algebra are also developed. Nonassociative quantum algebras in terms of position and momentum operators are given as the simplest examples of a framework whose applications may involve string theory and nonlinear quantum field theory.
Stability of the extremal Reissner-Nordström black hole to charged scalar perturbations
International Nuclear Information System (INIS)
The stability of Reissner-Nordström black holes to neutral (gravitational and electromagnetic) perturbations was established almost four decades ago. However, the stability of these charged black holes under charged perturbations has remained an open question due to the well-known phenomena of superradiant scattering: A charged scalar field impinging on a charged Reissner-Nordström black hole can be amplified as it scatters off the hole. If the incident field has a non-zero rest mass, then the mass term effectively works as a mirror, preventing the energy extracted from the hole from escaping to infinity. One may suspect that such superradiant amplification of charged fields in Reissner-Nordström spacetimes may lead to an instability of these charged black holes (in as much the same way that rotating Kerr black holes are unstable under rotating scalar perturbations). However, we show here that, for extremal Reissner-Nordström black holes, the two conditions which are required in order to trigger a possible superradiant instability [namely: (1) the existence of a trapping potential well outside the black hole, and (2) superradiant amplification of the trapped modes] cannot be satisfied simultaneously. Our results thus support the stability of extremal Reissner-Nordström black holes to charged scalar perturbations.
Casimir Effect of Scalar Massive Field
Mobassem, Sonia
2014-01-01
The energy momentum tensor is used to introduce the Casimir force of the massive scalar field acting on a nonpenetrating surface. This expression can be used to evaluate the vacuum force by employing the appropriate field operators. To simplify our formalism we also relates the vacuum force expression to the imaginary part of the Green function via the fluctuation dissipation theorem and Kubo formula. This allows one to evaluate the vacuum force without resorting to the process of field quantization. These two approaches are used to calculate the attractive force between two nonpenetrating plates. Special attention is paid to the generalization of the formalism to D + 1 space-time dimensions.
Li, Ran; Zhang, Hongbao; Zhao, Junkun(Department of Physics, Henan Normal University, 453007, Xinxiang, China)
2016-01-01
Reissner-Nordstr\\"om Anti-de Sitter (RNAdS) black holes are unstable against the charged scalar field perturbations due to the well-known superradiance phenomenon. We present the time domain analysis of charged scalar field perturbations in the RNAdS black hole background in general dimensions. We show that the instabilities of charged scalar field can be explicitly illustrated from the time profiles of evolving scalar field. By using the Prony method to fit the time evolution data, we confir...
Chakrabortty, Joydeep; Mondal, Subhadeep; Srivastava, Tripurari
2015-01-01
In this work, we investigate the phenomenological consequences of a doubly charged scalar which may belong to different uncoloured scalar multiplets. This doubly charged scalar couples to the charged leptons as well as gauge bosons, which we parametrize in a model independent way. Restricting ourselves in the regime of conserved charged-parity (CP), we assume only a few non-zero Yukawa couplings ($y_{\\mu \\ell}$, where $\\ell=e,\\mu,\\tau$) between the doubly charged scalar and the charged leptons. Our choices allow the doubly charged scalar to impinge low-energy processes like anomalous magnetic moment of muon and a few possible charged lepton flavour violating (CLFV) processes. These same Yukawa couplings are also instrumental in producing same-sign di-lepton signatures at the LHC. In this article we examine the impact of individual contributions from the diagonal and off-diagonal Yukawa couplings in the light of muon $(g-2)$ excess. Subsequently, we use the derived information to inquire the possible CLFV proc...
Slowly rotating neutron stars in scalar-tensor theories with a massive scalar field
Yazadjiev, Stoytcho S; Popchev, Dimitar
2016-01-01
In the scalar-tensor theories with a massive scalar field the coupling constants, and the coupling functions in general, which are observationally allowed, can differ significantly from those in the massless case. This fact naturally implies that the scalar-tensor neutron stars with a massive scalar field can have rather different structure and properties in comparison with their counterparts in the massless case and in general relativity. In the present paper we study slowly rotating neutron stars in scalar-tensor theories with a massive gravitational scalar. Two examples of scalar-tensor theories are examined - the first example is the massive Brans-Dicke theory and the second one is a massive scalar-tensor theory indistinguishable from general relativity in the weak field limit. In the later case we study the effect of the scalar field mass on the spontaneous scalarization of neutron stars. Our numerical results show that the inclusion of a mass term for the scalar field indeed changes the picture drastica...
Quantum tunneling from scalar fields in rotating black strings
Gohar, H
2011-01-01
Using the Hamilton-Jacobi method of quantum tunneling and complex path integration, we study Hawking radiation of scalar particles from rotating black strings. We discuss tunneling of both charged and uncharged scalar particles from the event horizons. For this purpose, we use the Klein-Gordon equation and find the tunneling probability of outging scalar particles. The procedure gives Hawking temperature for rotating charged black strings as well.
Quantum tunneling from scalar fields in rotating black strings
Gohar, H.; Saifullah, K.
2013-08-01
Using the Hamilton-Jacobi method of quantum tunneling and complex path integration, we study Hawking radiation of scalar particles from rotating black strings. We discuss tunneling of both charged and uncharged scalar particles from the event horizons. For this purpose, we use the Klein-Gordon equation and find the tunneling probability of outgoing scalar particles. The procedure gives Hawking temperature for rotating charged black strings as well.
Scalar fields properties for flat galactic rotation curves
Fay, S
2004-01-01
The whole class of minimally coupled and massive scalar fields which may be responsible for flattening of galactic rotation curves is found. An interesting relation with a class of scalar-tensor theories able to isotropise anisotropic models of Universe is shown. The resulting metric is found and its stability and scalar field properties are tested with respect to the presence of a second scalar field or a small perturbation of the rotation velocity at galactic outer radii.
Twinlike models in scalar field theories
International Nuclear Information System (INIS)
This work deals with the presence of defect structures in models described by a real scalar field in a diversity of scenarios. The defect structures that we consider are static solutions of the equations of motion that depend on a single spatial dimension. We search for different models, which support the same defect solution, with the very same energy density. We work in flat spacetime, where we introduce and investigate a new class of models. We also work in curved spacetime, within the braneworld context, with a single extra dimension of infinite extent, and there we show how the brane is formed from the static field configuration.
Generalized Gravitational Entropy of Interacting Scalar Field and Maxwell Field
Huang, Wung-Hong
2014-01-01
The generalized gravitational entropy proposed by Lewkowycz and Maldacena in recent is extended to the interacting real scalar field and Maxwell field system. Using the BTZ geometry we first investigate the case of free real scalar field and then show a possible way to calculate the entropy of the interacting scalar field. Next, we investigate the Maxwell field system. We exactly solve the wave equation and calculate the analytic value of the generalized gravitational entropy. We also use the Einstein equation to find the effect of backreaction of the Maxwell field on the spacetime. The associated modified area law is consistent with the generalized gravitational entropy. Our investigations have not found the unexpected anomalous surface term.
Vacuum polarization of a scalar field in wormhole spacetimes
Popov, A A; Popov, Arkadii A.; Sushkov, Sergey V.
2001-01-01
An analitical approximation of $$ for a scalar field in a static spherically symmetric wormhole spacetime is obtained. The scalar field is assumed to be both massive and massless, with an arbitrary coupling $\\xi$ to the scalar curvature, and in a zero temperature vacuum state.
Thermodynamic phase structure of charged anti-de Sitter scalar-tensor black holes
International Nuclear Information System (INIS)
When electromagnetic field with nonlinear lagrangian acts as a source of gravity the no-scalar-hair theorems can be eluded and black holes with non-trivial scalar field can be found in scalar tensor theories. Black holes with secondary scalar hair exist also when a cosmological constant is added in the theory. The thermodynamics of black holes in anti-de Sitter (AdS) space-time has attracted considerable interest due to the AdS/CFT conjecture. A natural question that arises is whether the non-trivial scalar field would alter the black-hole thermodynamical phase structure. In the current work we present the phase structure of charged hairy black holes coupled to nonlinear Born-Infeld electrodynamics in canonical ensemble which is naturally related to AdS space-time. In certain regions of the parameter space we find the existence of a first-order phase transition between small and very large black holes. An unexpected result is that for a small subinterval of charge values two phase transitions are observed – one of zeroth and one of first order
General Relativity, Scalar Fields and Cosmic Strings.
Burd, Adrian Benedict
1987-09-01
Available from UMI in association with The British Library. This thesis is divided into three, essentially self-contained, parts. In the first part we examine the structure of classical three-dimensional space-times. Here, we review and extend what is known about the gravitational theories in these models. We investigate the non-existence of a Newtonian limit to the relativistic theories showing that in the presence of certain matter terms, Newtonian gravity can be obtained as a suitable weak-field limit. We present a number of new, exact static and non-static solutions to the equations of three-dimensional general relativity with scalar field and perfect fluid sources. We comment on the relationship between the stiff perfect fluid and the scalar field. Motivated by the Kaluza-Klein procedure of dimensional reduction we find some exact scalar field solutions which have analogues in four-dimensions. We also present classification schemes based on the group of motions of homogeneous space-times and on the Cotton -York tensor. The description of the general cosmological solution in the vicinity of the singularity is given in terms of the number of arbitrary spatial functions independently specified on a space-like hypersurface. We also study a series approximation to the space-time in the vicinity of the cosmological singularity. Some conjectures are made concerning the space-time singularities. We present two exact cosmological solutions containing self-interacting scalar fields. The models exhibit an inflationary behaviour. We also present an anisotropic cosmological model. The second part of the thesis contains a study of certain cosmological models which have self-interacting scalar fields obeying an exponential potential. We use the techniques of phase portrait analysis to study the N-dimensional cosmological models as well as certain anisotropic models. The latter involves the analysis of a three-dimensional system of equations and we review the relevant theory
Scalar field collapse with negative cosmological constant
Baier, R.; Nishimura, H.; Stricker, S. A.
2015-07-01
The formation of black holes or naked singularities is studied in a model in which a homogeneous time-dependent scalar field with an exponential potential couples to four-dimensional gravity with negative cosmological constant. An analytic solution is derived and its consequences are discussed. The model depends only on one free parameter, which determines the equation of state and decides the fate of the spacetime. Without fine tuning the value of this parameter the collapse ends in a generic formation of a black hole or a naked singularity. The latter case violates the cosmic censorship conjecture.
Scalar field collapse with negative cosmological constant
Baier, R; Stricker, S A
2014-01-01
The formation of black holes or naked singularities is studied in a model in which a homogeneous time-dependent scalar field with an exponential potential couples to four dimensional gravity with negative cosmological constant. An analytic solution is derived and its consequences are discussed. The model depends only on one free parameter which determines the equation of state and decides the fate of the spacetime. Depending on the value of this parameter the collapse ends in a black hole or a naked singularity. The latter case violates the cosmic censorship conjecture.
Induced gravity I: real scalar field
Einhorn, Martin B.; Jones, D. R. Timothy
2016-01-01
We show that classically scale invariant gravity coupled to a single scalar field can undergo dimensional transmutation and generate an effective Einstein-Hilbert action for gravity, coupled to a massive dilaton. The same theory has an ultraviolet fixed point for coupling constant ratios such that all couplings are asymptotically free. However the catchment basin of this fixed point does not include regions of coupling constant parameter space compatible with locally stable dimensional transmutation. In a companion paper, we will explore whether this more desirable outcome does obtain in more complicated theories with non-Abelian gauge interactions.
Scalar-field theory of dark matter
Huang, Kerson; Zhao, Xiaofei
2013-01-01
We develop a theory of dark matter based on a previously proposed picture, in which a complex vacuum scalar field makes the universe a superfluid, with the energy density of the superfluid giving rise to dark energy, and variations from vacuum density giving rise to dark matter. We formulate a nonlinear Klein-Gordon equation to describe the superfluid, treating galaxies as external sources. We study the response of the superfluid to the galaxies, in particular, the emergence of the dark-matter galactic halo, contortions during galaxy collisions, and the creation of vortices due to galactic rotation.
Induced Gravity I: Real Scalar Field
Einhorn, Martin B
2016-01-01
We show that classically scale invariant gravity coupled to a single scalar field can undergo dimensional transmutation and generate an effective Einstein-Hilbert action for gravity, coupled to a massive dilaton. The same theory has an ultraviolet fixed point for coupling constant ratios such that all couplings are asymptotically free. However the catchment basin of this fixed point does not include regions of coupling constant parameter space compatible with locally stable dimensional transmutation. We believe that the desirable outcome may obtain in more complicated theories with non-Abelian gauge interactions.
Frolov, Valeri P.; Zelnikov, Andrei
2012-03-01
We study massless scalar and electromagnetic fields from static sources in a static higher-dimensional spacetime. Exact expressions for static Green’s functions for such problems are obtained in the background of the Majumdar-Papapetrou solutions of the Einstein-Maxwell equations. Using this result, we calculate the force between two scalar or electric charges in the presence of one or several extremally charged black holes in equilibrium in the higher-dimensional spacetime.
Scalar field dark matter and the Higgs field
Bertolami, O.; Catarina Cosme; Rosa, João G.
2016-01-01
We discuss the possibility that dark matter corresponds to an oscillating scalar field coupled to the Higgs boson. We argue that the initial field amplitude should generically be of the order of the Hubble parameter during inflation, as a result of its quasi-de Sitter fluctuations. This implies that such a field may account for the present dark matter abundance for masses in the range 10−6–10−4eV, if the tensor-to-scalar ratio is within the range of planned CMB experiments. We show that such ...
Dynamical analysis in scalar field cosmology
Paliathanasis, Andronikos; Tsamparlis, Michael; Basilakos, Spyros; Barrow, John D.
2015-06-01
We give a general method to find exact cosmological solutions for scalar-field dark energy in the presence of perfect fluids. We use the existence of invariant transformations for the Wheeler De Witt (WdW) equation. We show that the existence of a point transformation under which the WdW equation is invariant is equivalent to the existence of conservation laws for the field equations, which indicates the existence of analytical solutions. We extend previous work by providing exact solutions for the Hubble parameter and the effective dark-energy equation of state parameter for cosmologies containing a combination of perfect fluid and a scalar field whose self-interaction potential is a power of hyperbolic functions. We find solutions explicitly when the perfect fluid is radiation or cold dark matter and determine the effects of nonzero spatial curvature. Using the Planck 2015 data, we determine the evolution of the effective equation of state of the dark energy. Finally, we study the global dynamics using dimensionless variables. We find that if the current cosmological model is Liouville integrable (admits conservation laws) then there is a unique stable point which describes the de-Sitter phase of the universe.
Higgs and gravitational scalar fields together induce Weyl gauge
Scholz, Erhard
2014-01-01
A common biquadratic potential for the Higgs field $h$ and an additional scalar field $\\phi$, non minimally coupled to gravity, is considered in locally scale symmetric approaches to standard model fields in curved spacetime. A common ground state of the two scalar fields exists and couples both fields to gravity, more precisely to scalar curvature $R$. In Einstein gauge ($\\phi = const$, often called "Einstein frame"), also $R$ is scaled to a constant. This condition makes perfect sense, even...
Scalar field dark matter and the Higgs field
Bertolami, O.; Cosme, Catarina; Rosa, João G.
2016-08-01
We discuss the possibility that dark matter corresponds to an oscillating scalar field coupled to the Higgs boson. We argue that the initial field amplitude should generically be of the order of the Hubble parameter during inflation, as a result of its quasi-de Sitter fluctuations. This implies that such a field may account for the present dark matter abundance for masses in the range 10-6-10-4eV, if the tensor-to-scalar ratio is within the range of planned CMB experiments. We show that such mass values can naturally be obtained through either Planck-suppressed non-renormalizable interactions with the Higgs boson or, alternatively, through renormalizable interactions within the Randall-Sundrum scenario, where the dark matter scalar resides in the bulk of the warped extra-dimension and the Higgs is confined to the infrared brane.
Scalar field dark matter and the Higgs field
Directory of Open Access Journals (Sweden)
O. Bertolami
2016-08-01
Full Text Available We discuss the possibility that dark matter corresponds to an oscillating scalar field coupled to the Higgs boson. We argue that the initial field amplitude should generically be of the order of the Hubble parameter during inflation, as a result of its quasi-de Sitter fluctuations. This implies that such a field may account for the present dark matter abundance for masses in the range 10−6–10−4eV, if the tensor-to-scalar ratio is within the range of planned CMB experiments. We show that such mass values can naturally be obtained through either Planck-suppressed non-renormalizable interactions with the Higgs boson or, alternatively, through renormalizable interactions within the Randall–Sundrum scenario, where the dark matter scalar resides in the bulk of the warped extra-dimension and the Higgs is confined to the infrared brane.
Scalar field dark matter and the Higgs field
Bertolami, Orfeu; Rosa, João G
2016-01-01
We discuss the possibility that dark matter corresponds to an oscillating scalar field coupled to the Higgs boson. We argue that the initial field amplitude should generically be of the order of the Hubble parameter during inflation, as a result of its quasi-de Sitter fluctuations. This implies that such a field may account for the present dark matter abundance for masses in the range $10^{-6} - 10^{-4}$ eV, if the tensor-to-scalar ratio is within the range of planned CMB experiments. We show that such mass values can naturally be obtained through either Planck-suppressed non-renormalizable interactions with the Higgs boson or, alternatively, through renormalizable interactions within the Randall-Sundrum scenario, where the dark matter scalar resides in the bulk of the warped extra-dimension and the Higgs is confined to the infrared brane.
Scalar Field Theories with Polynomial Shift Symmetries
Griffin, Tom; Horava, Petr; Yan, Ziqi
2014-01-01
We continue our study of naturalness in nonrelativistic QFTs of the Lifshitz type, focusing on scalar fields that can play the role of Nambu-Goldstone (NG) modes associated with spontaneous symmetry breaking. Such systems allow for an extension of the constant shift symmetry to a shift by a polynomial of degree $P$ in spatial coordinates. These "polynomial shift symmetries" in turn protect the technical naturalness of modes with a higher-order dispersion relation, and lead to a refinement of the proposed classification of infrared Gaussian fixed points available to describe NG modes in nonrelativistic theories. Generic interactions in such theories break the polynomial shift symmetry explicitly to the constant shift. It is thus natural to ask: Given a Gaussian fixed point with polynomial shift symmetry of degree $P$, what are the lowest-dimension operators that preserve this symmetry, and deform the theory into a self-interacting scalar field theory with the shift symmetry of degree $P$? To answer this (essen...
Searching for Chameleon-Like Scalar Fields
Levshakov, S. A.; Molaro, P.; Kozlov, M. G.; Lapinov, A. V.; Henkel, Ch.; Reimersi, D.; Sakai, T.; Agafonova, I. I.
Using the 32-m Medicina, 45-m Nobeyama, and 100-m Effelsberg telescopes we found a statistically significant velocity offset ΔV ≈ 27 ± 3 m s - 1 (1σ) between the inversion transition in NH3(1,1) and low-J rotational transitions in N2H + (1-0) and HC3N(2-1) arising in cold and dense molecular cores in the Milky Way. Systematic shifts of the line centers caused by turbulent motions and velocity gradients, possible non-thermal hyperfine structure populations, pressure and optical depth effects are shown to be lower than or about 1 m s - 1 and thus can be neglected in the total error budget. The reproducibility of ΔV at the same facility (Effelsberg telescope) on a year-to-year basis is found to be very good. Since the frequencies of the inversion and rotational transitions have different sensitivities to variations in μ ≡ m e / m p, the revealed non-zero ΔV may imply that μ changes when measured at high (terrestrial) and low (interstellar) matter densities as predicted by chameleon-like scalar field models - candidates to the dark energy carrier. Thus we are testing whether scalar field models have chameleon-type interactions with ordinary matter. The measured velocity offset corresponds to the ratio Δμ / μ ≡ (μspace - μlab) / μlab of (26 ± 3) ×10 - 9 (1σ).
Creation of the universe with a stealth scalar field
Maeda, Hideki
2012-01-01
The stealth scalar field is a non-trivial configuration without any back-reaction to geometry, which is characteristic for non-minimally coupled scalar fields. Studying the creation probability of the de Sitter universe with a stealth scalar field by the Hartle and Hawking's semi-classical method, we show that the effect of the stealth field can be significant. For the class of scalar fields we consider, creation of the universe with a stealth field is possible for a discrete value of the coupling constant and its creation rate is almost the same as that of the universe in vacuum.
AdS (instability: Lessons from the scalar field
Directory of Open Access Journals (Sweden)
Pallab Basu
2015-06-01
Full Text Available We argued in arXiv:1408.0624 that the quartic scalar field in AdS has features that could be instructive for answering the gravitational stability question of AdS. Indeed, the conserved charges identified there have recently been observed in the full gravity theory as well. In this paper, we continue our investigation of the scalar field in AdS and provide evidence that in the Two-Time Formalism (TTF, even for initial conditions that are far from quasi-periodicity, the energy in the higher modes at late times is exponentially suppressed in the mode number. Based on this and some related observations, we argue that there is no thermalization in the scalar TTF model within time-scales that go as ∼1/ϵ2, where ϵ measures the initial amplitude (with only low-lying modes excited. It is tempting to speculate that the result holds also for AdS collapse.
Massive scalar field evolution in de Sitter
Markkanen, Tommi
2016-01-01
The behaviour of a massive, non-interacting and non-minimally coupled quantised scalar field in an expanding de Sitter background is investigated by solving the field evolution for an arbitrary initial state. In this approach there is no need to choose a vacuum in order to provide a definition for particle states. We conclude that the expanding de Sitter space is a stable equilibrium configuration under small perturbations of the initial conditions. Depending on the initial state, the energy density can approach its asymptotic value from above or below, the latter of which implies a violation of the weak energy condition. The backreaction of the quantum corrections can therefore lead to a phase of super-acceleration also in the non-interacting massive case.
Grassmann scalar fields and asymptotic freedom
International Nuclear Information System (INIS)
The authors extend previous results about scalar fields whose Fourier components are even elements of a Grassmann algebra with given index of nilpotency. Their main interest in particle physics is related to the possibility that they describe fermionic composites analogous to the Copper pairs of superconductivity. The authors evaluate the free propagators for arbitrary index of nilpotency and they investigate a φ4 model to one loop. Due to the nature of the integral over even Grassmann fields such as a model exists for repulsive as well as attractive self interaction. In the first case the β-function is equal to that of the ordinary theory, while in the second one the model is asymptotically free. The bare mass has a peculiar dependence on the cutoff, being quadratically decreasing/increasing for attractive/repulsive self interaction
Landau levels of scalar QED in time-dependent magnetic fields
International Nuclear Information System (INIS)
The Landau levels of scalar QED undergo continuous transitions under a homogeneous, time-dependent magnetic field. We analytically formulate the Klein–Gordon equation for a charged spinless scalar as a Cauchy initial value problem in the two-component first order formalism and then put forth a measure that classifies the quantum motions into the adiabatic change, the nonadiabatic change, and the sudden change. We find the exact quantum motion and calculate the pair-production rate when the magnetic field suddenly changes as a step function. -- Highlights: •We study the Landau levels of scalar QED in time-dependent magnetic fields. •Instantaneous Landau levels make continuous transitions but keep parity. •The Klein–Gordon equation is expressed in the two-component first order formalism. •A measure is advanced that characterizes the quantum motions into three categories. •A suddenly changing magnetic field produces pairs of charged scalars from vacuum
Imprint of thawing scalar fields on large scale galaxy overdensity
Dinda, Bikash R
2016-01-01
We calculate the observed galaxy power spectrum for the thawing class of scalar field models taking into account various general relativistic corrections that occur on very large scales. As we need to consider the fluctuations in scalar field on these large scales, the general relativistic corrections in thawing scalar field models are distinctly different from $\\Lambda$CDM and the difference can be upto $15-20\\%$ at some scales. Also there is an interpolation between suppression and enhancement of power in scalar field models compared to the $\\Lambda$CDM model on smaller scales and this happens in a specific redshift range that is quite robust to the form of the scalar field potentials or the choice of different cosmological parameters. This can be useful to distinguish scalar field models from $\\Lambda$CDM with future optical/radio surveys.
Massive basketball diagram for a thermal scalar field theory
Andersen, Jens O.; Braaten, Eric; Strickland, Michael
2000-08-01
The ``basketball diagram'' is a three-loop vacuum diagram for a scalar field theory that cannot be expressed in terms of one-loop diagrams. We calculate this diagram for a massive scalar field at nonzero temperature, reducing it to expressions involving three-dimensional integrals that can be easily evaluated numerically. We use this result to calculate the free energy for a massive scalar field with a φ4 interaction to three-loop order.
Lagrange Multipliers and Third Order Scalar-Tensor Field Theories
Horndeski, Gregory W
2016-01-01
In a space of 4-dimensions, I will examine constrained variational problems in which the Lagrangian, and constraint scalar density, are concomitants of a (pseudo-Riemannian) metric tensor and its first two derivatives. The Lagrange multiplier for these constrained extremal problems will be a scalar field. For suitable choices of the Lagrangian, and constraint, we can obtain Euler-Lagrange equations which are second order in the scalar field and third order in the metric tensor. The effect of disformal transformations on the constraint Lagrangians, and their generalizations, is examined. This will yield other second order scalar-tensor Lagrangians which yield field equations which are at most of third order. No attempt is made to construct all possible third order scalar-tensor Euler-Lagrange equations in a 4-space, although nine classes of such field equations are presented. Two of these classes admit subclasses which yield conformally invariant field equations. A few remarks on scalar-tensor-connection theor...
Self-interacting complex scalar field as dark matter
International Nuclear Information System (INIS)
We study the viability of a a complex scalar field χ with self-interacting potential V = m0χ/2|χ|2+h|χ|4 as dark matter. Due to the self interaction, the scalar field forms a Bose-Einstein condensate at early times that represents dark matter. The self interaction is also responsible of quantum corrections to the scalar field mass that naturally give the dark matter domination at late times without any fine tuning on the energy density of the scalar field at early times. Finally the properties of the spherically symmetric dark matter halos are also discussed.
One-loop quantum corrections to cosmological scalar field potentials
Arbey, A; Arbey, Alexandre; Mahmoudi, Farvah
2007-01-01
We study the loop corrections to potentials of complex or coupled real scalar fields used in cosmology to account for dark energy, dark matter or dark fluid. We show that the SUGRA quintessence and dark matter scalar field potentials are stable against the quantum fluctuations, and we propose solutions to the instability of the potentials of coupled quintessence and dark fluid scalar fields. We also find that a coupling to fermions is very restricted, unless this coupling has a structure which already exists in the scalar field potential or which can be compensated by higher order corrections. Finally, we study the influence of the curvature and kinetic term corrections.
Scalar field confinement as a model for accreting systems
Energy Technology Data Exchange (ETDEWEB)
Megevand, M [Department of Physics and Astronomy, Louisiana State University, 202 Nicholson Hall, Baton Rouge, LA 70803-4001 (United States); Olabarrieta, I [Department of Physics and Astronomy, Louisiana State University, 202 Nicholson Hall, Baton Rouge, LA 70803-4001 (United States); Lehner, L [Department of Physics and Astronomy, Louisiana State University, 202 Nicholson Hall, Baton Rouge, LA 70803-4001 (United States)
2007-07-07
We investigate the possibility of localizing scalar field configurations as a model for black hole accretion. We analyse and resolve difficulties encountered when localizing scalar fields in general relativity. We illustrate this ability with a simple spherically symmetric model which can be used to study features of accreting shells around a black hole. This is accomplished by prescribing a scalar field with a coordinate-dependent potential. Numerical solutions to the Einstein-Klein-Gordon equations are shown, where a scalar field is indeed confined within a region surrounding a black hole. The resulting spacetime can be described in terms of simple harmonic time dependence.
Accelerating cosmology in modified gravity with scalar field
Shaido, Yulia A.; Sugamoto, Akio
2004-01-01
The modified gravity with 1/R term (R being scalar curvature) and the Einstein-Hilbert term is studied by incorporating the phantom scalar field. A number of cosmological solutions are derived in the presence of the phantom field in the perfect fluid background. It is shown the current inflation obtained in the modified gravity is affected by the existence the phantom field.
Geometrization conditions for perfect fluids, scalar fields, and electromagnetic fields
Krongos, D. S.; Torre, C. G.
2015-07-01
Rainich-type conditions giving a spacetime "geometrization" of matter fields in general relativity are reviewed and extended. Three types of matter are considered: perfect fluids, scalar fields, and electromagnetic fields. Necessary and sufficient conditions on a spacetime metric for it to be part of a perfect fluid solution of the Einstein equations are given. Formulas for constructing the fluid from the metric are obtained. All fluid results hold for any spacetime dimension. Geometric conditions on a metric which are necessary and sufficient for it to define a solution of the Einstein-scalar field equations and formulas for constructing the scalar field from the metric are unified and extended to arbitrary dimensions, to include a cosmological constant, and to include any self-interaction potential. Necessary and sufficient conditions on a four-dimensional spacetime metric for it to be an electrovacuum and formulas for constructing the electromagnetic field from the metric are generalized to include a cosmological constant. Both null and non-null electromagnetic fields are treated. A number of examples and applications of these results are presented.
Harmonic bilocal fields generated by globally conformal invariant scalar fields
International Nuclear Information System (INIS)
The twist two contribution in the operator product expansion of φ1(x1) φ2(x2) for a pair of globally conformal invariant, scalar fields of equal scaling dimension d in four space-time dimensions is a field V1(x1, x2) which is harmonic in both variables. It is demonstrated that the Huygens bilocality of V1 can be equivalently characterized by a 'single-pole property' concerning the pole structure of the (rational) correlation functions involving the product φ1(x1) φ2(x2). This property is established for the dimension d = 2 of φ1, φ2. As an application we prove that any GCI scalar field of conformal dimension 2 (in four space-time dimensions) can be written as a (possibly infinite) superposition of products of free massless fields. (author)
Inflationary solutions in the nonminimally coupled scalar field theory
Koh, Seoktae; Kim, Sang Pyo; Song, Doo Jong
2005-08-01
We study analytically and numerically the inflationary solutions for various type scalar potentials in the nonminimally coupled scalar field theory. The Hamilton-Jacobi equation is used to deal with nonlinear evolutions of inhomogeneous spacetimes and the long-wavelength approximation is employed to find the homogeneous solutions during an inflation period. The constraints that lead to a sufficient number of e-folds, a necessary condition for inflation, are found for the nonminimal coupling constant and initial conditions of the scalar field for inflation potentials. In particular, we numerically find an inflationary solution in the new inflation model of a nonminimal scalar field.
Scalar field dark matter: behavior around black holes
International Nuclear Information System (INIS)
We present the numerical evolution of a massive test scalar fields around a Schwarzschild space-time. We proceed by using hyperboloidal slices that approach future null infinity, which is the boundary of scalar fields, and also demand the slices to penetrate the event horizon of the black hole. This approach allows the scalar field to be accreted by the black hole and to escape toward future null infinity. We track the evolution of the energy density of the scalar field, which determines the rate at which the scalar field is being diluted. We find polynomial decay of the energy density of the scalar field, and use it to estimate the rate of dilution of the field in time. Our findings imply that the energy density of the scalar field decreases even five orders of magnitude in time scales smaller than a year. This implies that if a supermassive black hole is the Schwarzschild solution, then scalar field dark matter would be diluted extremely fast
Boundary Conditions as Mass Generation Mechanism for Complex Scalar Fields
Nogueira, J A
2003-01-01
We consider the effects of homogeneous Dirichlet's boundary conditions in the scalar electrodynamics with self-interaction. We have found for a critical scale of the compactification length that symmetry is restored and scalar field develops mass and vector field does not.
Boundary Conditions as Mass Generation Mechanism for Real Scalar Fields
Nogueira, J A; Nogueira, Jose Alexandre; Barbieri, Pedro Leite
2001-01-01
We consider the effects of homogeneous Dirichlet's boundary conditions on two infinite parallel plane surfaces separated by a small distance {\\it a}. We find that although spontaneous symmetry breaking does not occur for the theory of a massless, quartically self-interacting real scalar field, the theory becomes a theory of a massive scalar field.
Entropy of Scalar Field near a Schwarzschild Black Hole Horizon
Setare, M.R.(Department of Science, University of Kurdistan, Campus of Bijar, Bijar, Iran)
2005-01-01
In this paper we compute the correction to the entropy of Schwarzschild black hole due to the vacuum polarization effect of massive scalar field. The Schwarzschild black hole is supposed to be confined in spherical shell. The scalar field obeying mixed boundary condition on the spherical shell.
Effective Hamiltonian for non-minimally coupled scalar fields
Mese, Emine; Pirinccioglu, Nurettin; Acikgoz, Irfan; Binbay, Figen
2006-01-01
Performing a relativistic approximation as the generalization to a curved spacetime of the flat space Klein-Gordon equation, an effective Hamiltonian which includes non-minimial coupling between gravity and scalar field and also quartic self-interaction of scalar field term is obtained.
Regular and Chaotic Regimes in Scalar Field Cosmology
Directory of Open Access Journals (Sweden)
Alexey V. Toporensky
2006-03-01
Full Text Available A transient chaos in a closed FRW cosmological model with a scalar field is studied. We describe two different chaotic regimes and show that the type of chaos in this model depends on the scalar field potential. We have found also that for sufficiently steep potentials or for potentials with large cosmological constant the chaotic behavior disappears.
Decoding the hologram: Scalar fields interacting with gravity
Kabat, Daniel
2013-01-01
We construct smeared CFT operators which represent a scalar field in AdS interacting with gravity. The guiding principle is micro-causality: scalar fields should commute with themselves at spacelike separation. To O(1/N) we show that a correct and convenient criterion for constructing the appropriate CFT operators is to demand micro-causality in a three-point function with a boundary Weyl tensor and another boundary scalar. The resulting bulk observables transform in the correct way under AdS isometries and commute with boundary scalar operators at spacelike separation, even in the presence of metric perturbations.
Landau Levels of Scalar QED in Time-Dependent Magnetic Fields
Kim, Sang Pyo
2013-01-01
The Landau levels of scalar QED undergo continuous transitions under a homogeneous, time-dependent magnetic field. We analytically formulate the Klein-Gordon equation for a charged spinless scalar as a Cauchy initial value problem in the two-component first order formalism and then put forth a measure that classifies the quantum motions into the adiabatic change, the nonadiabatic change, and the sudden change. We find the exact quantum motion and calculate the pair-production rate when the ma...
Effective field theory of quantum gravity coupled to scalar electrodynamics
Ibiapina Bevilaqua, L.; Lehum, A. C.; da Silva, A. J.
2016-05-01
In this work, we use the framework of effective field theory to couple Einstein’s gravity to scalar electrodynamics and determine the renormalization of the model through the study of physical processes below Planck scale, a realm where quantum mechanics and general relativity are perfectly compatible. We consider the effective field theory up to dimension six operators, corresponding to processes involving one-graviton exchange. Studying the renormalization group functions, we see that the beta function of the electric charge is positive and possesses no contribution coming from gravitational interaction. Our result indicates that gravitational corrections do not alter the running behavior of the gauge coupling constants, even if massive particles are present.
Covariant and gauge-invariant linear scalar perturbations in multiple scalar field cosmologies
Alho, Artur
2013-01-01
We derive a set of equations monitoring the evolution of covariant and gauge-invariant linear scalar perturbations of Friedman-Lema\\^itre-Robertson-Walker models with multiple interacting non-linear scalar fields. We use a dynamical systems' approach in order to perform a stability analysis for some classes of scalar field potentials. In particular, using a recent approximation for the inflationary dynamics of the background solution, we derive conditions under which homogenization occurs for chaotic (quadratic and quartic potentials) and new inflation. We also prove a cosmic no-hair result for power-law inflation and its generalisation for two scalar fields with independent exponential potentials (assisted power-law inflation).
Fundamental scalar fields and the dark side of the universe
Mychelkin, Eduard G
2015-01-01
Starting with geometrical premises, we infer the existence of fundamental cosmological scalar fields. We then consider physically relevant situations in which spacetime metric is induced by one or, in general, by two scalar fields, in accord with the Papapetrou algorithm. The first of these fields, identified with dark energy, has exceedingly small but finite (subquantum) Hubble mass scale (~ 10^-33 eV), and might be represented as a neutral superposition of quasi-static electric fields. The second field is identified with dark matter as an effectively scalar conglomerate composed of primordial neutrinos and antineutrinos in a special tachyonic state.
Searching for Chameleon-like Scalar Fields
Levshakov, S A; Kozlov, M G; Lapinov, A V; Henkel, C; Reimers, D; Sakai, T; Agafonova, I I
2010-01-01
Using the 32-m Medicina, 45-m Nobeyama, and 100-m Effelsberg telescopes we found a statistically significant velocity offset Delta V = 27 +/- 3 m/s (1sigma) between the inversion transition in NH3(1,1) and low-J rotational transitions in N2H+(1-0) and HC3N(2-1) arising in cold and dense molecular cores in the Milky Way. Systematic shifts of the line centers caused by turbulent motions and velocity gradients, possible non-thermal hyperfine structure populations, pressure and optical depth effects are shown to be lower than or about 1 m/s and thus can be neglected in the total error budget. The reproducibility of Delta V at the same facility (Effelsberg telescope) on a year-to-year basis is found to be very good. Since the frequencies of the inversion and rotational transitions have different sensitivities to variations in mu = m_e/m_p, the revealed non-zero Delta V may imply that mu changes when measured at high (terrestrial) and low (interstellar) matter densities as predicted by chameleon-like scalar field m...
Fundamental scalar fields and the dark side of the universe
Mychelkin, Eduard G.; Makukov, Maxim A.
2015-01-01
Starting with geometrical premises, we infer the existence of fundamental cosmological scalar fields. We then consider physically relevant situations in which spacetime metric is induced by one or, in general, by two scalar fields, in accord with the Papapetrou algorithm. The first of these fields, identified with dark energy, has exceedingly small but finite (subquantum) Hubble mass scale (~ 10^-33 eV), and might be represented as a neutral superposition of quasi-static electric fields. The ...
On the entanglement between interacting scalar field theories
Mozaffar, M. Reza Mohammadi; Mollabashi, Ali
2016-03-01
We study "field space entanglement" in certain quantum field theories consisting of N number of free scalar fields interacting with each other via kinetic mixing terms. We present exact analytic expressions for entanglement and Renyi entropies between arbitrary numbers of scalar fields by which we could explore certain entanglement inequalities. Other entanglement measures such as mutual information and entanglement negativity have also been studied. We also give some comments about possible holographic realizations of such models.
GFFD： Generalized free-form deformation with scalar fields
Institute of Scientific and Technical Information of China (English)
秦绪佳; 华炜; 方向; 鲍虎军; 彭群生
2003-01-01
The novel free-form deformation (FFD) technique presented in the paper uses scalar fields definedby skeletons with arbitrary topology. The technique embeds objects into the scalar field by assigning a field value to each point of the objects. When the space of the skeleton is changed, the distribution of the scalar field changes accordingly, which implicitly defines a deformation of the space. The generality of skeletons assures that the technique can freely define deformable regions to produce a broader range of shape deformations.
Hawking radiation of scalars from charged accelerating and rotating black holes with NUT parameter
Jan, Khush
2013-01-01
We study the quantum tunneling of scalars from charged accelerating and rotating black hole with NUT parameter. For this purpose we use the charged Klein-Gordon equation. We apply WKB approximation and the Hamilton-Jacobi method to solve charged the Klein-Gordon equation. We find the tunneling probability of outgoing charged scalars from the event horizon of this black hole, and hence the Hawking temperature for this black hole.
Charged Scalar Phenomenology in the Bilinear R-Parity Breaking Model
Ferrandis, J
1998-01-01
We consider the charged scalar boson phenomenology in the bilinear R-parity breaking model which induces a mixing between staus and the charged Higgs boson. The charged Higgs boson mass can be lower than expected in the MSSM, even before including radiative corrections. The R-parity violating decay rates can be comparable or even bigger than the R-parity conserving ones. These features could have implications for charged supersymmetric scalar boson searches at future accelerators.
Fast-roll solutions from two scalar field inflation
Santos, J R L
2015-01-01
The cosmological equations of motion of scalar fields are commonly not easy to be analytically solved, which makes necessary to use approximation methods, as the {\\it slow-roll} regime. In such an approximation one considers the scalar field potentials to be nearly flat. On the other hand, the so called {\\it fast-roll} regime considers exactly flat potentials. Our purpose in this work is to obtain solutions for a two scalar field quintessence model in the fast-roll regime. Cosmological interpretations for such solutions are also presented.
Critical gravity with a scalar field in four dimensions
Hirochi, Kyosuke
2012-01-01
We consider the critical gravity theory with a scalar field in four dimensions. We find that this theory has the solution corresponding to the de Sitter (dS), anti-de Sitter (AdS), and Minkowski background depending on whether the action includes the cosmological term or not. The Minkowski background is the solution which cannot be obtained in the model without a scalar field. At the critical point, we show that the Abbott-Deser (AD) mass of the Schwarzschild-de Sitter (SdS) black hole and the energy for the massless graviton vanish, whose situation is not changed from the model without a scalar field.
Cosmic string interactions induced by gauge and scalar fields
Kabat, Daniel; Sarkar, Debajyoti
2012-01-01
We study the interaction between two parallel cosmic strings induced by gauge fields and by scalar fields with non-minimal couplings to curvature. For small deficit angles the gauge field behaves like a collection of non-minimal scalars with a specific value for the non-minimal coupling. We check this equivalence by computing the interaction energy between strings at first order in the deficit angles. This result provides another physical context for the "contact terms" which play an importan...
General Analytical Solutions of Scalar Field Cosmology with Arbitrary Potential
Dimakis, N; Zampeli, Adamantia; Paliathanasis, Andronikos; Christodoulakis, T; Terzis, Petros A
2016-01-01
We present the solution space for the case of a minimally coupled scalar field with arbitrary potential in a FLRW metric. This is made possible due to the existence of a nonlocal integral of motion corresponding to the conformal Killing field of the two-dimensional minisuperspace metric. The case for both spatially flat and non flat are studied first in the presence of only the scalar field and subsequently with the addition of non interacting perfect fluids. It is verified that this addition does not change the general form of the solution, but only the particular expressions of the scalar field and the potential. The results are applied in the case of parametric dark energy models where we derive the scalar field equivalence solution for some proposed models in the literature.
Classical behavior of a scalar field in the inflationary universe
International Nuclear Information System (INIS)
Extending the coarse-graining approach of Starobinsky, we formulate a theory to deal with the dynamics of a scalar field in inflationary universe models. We find a set of classical Langevin equations which describes the large scale behavior of the scalar field, provided that the coarse-grained size is greater than the effective compton wavelength of the scalar field. The corresponding Fokker-Planck equation is also derived which is defined on the phase space of the scalar field. We show that our theory is essentially equivalent to the one-loop field theory in de Sitter space and reduces to that of Starobinsky in a strong limit of the slow roll-over condition. Analysis of a simple Higgs potential model is done and the implications are discussed. (author)
Scalar potential without cubic term in 3-3-1 models without exotic electric charges
Energy Technology Data Exchange (ETDEWEB)
Giraldo, Yithsbey [Universidad de Narino, Departamento de Fisica, A.A. 1175, Pasto (Colombia); Universidad de Antioquia, Instituto de Fisica, A.A. 1226, Medellin (Colombia); Ponce, William A. [Universidad de Antioquia, Instituto de Fisica, A.A. 1226, Medellin (Colombia)
2011-07-15
A detailed study of the criteria for stability of the scalar potential, and the proper electroweak symmetry breaking pattern in some 3-3-1 models without exotic electric charges is presented. In this paper we concentrate in a scalar sector with three Higgs scalar triplets, with a potential that does not include the cubic term, due to the presence of a discrete symmetry. For the analysis we use, and improve, a method previously developed to study the scalar potential in the two-Higgs-doublet extension of the standard model. Our main result is to show the consistency of those 3-3-1 models without exotic electric charges. (orig.)
Exact Inflationary Solution to Nonminimally Coupled Scalar Field
Institute of Scientific and Technical Information of China (English)
WANG Wen-Fu; YANG Shu-Zheng
2005-01-01
@@ We present a new exact inflationary solution to nonminimally coupled scalar field. The inflation is driven by the evolution of scalar field with inflation potential V() = λ/4()4 - 1/2m2()2 + Vo. This includes the solution that behaves exponential inflation for ()o ＞ () ＞ ()end and then develops smoothly towards radiation-like evolution for () ＜ (()end. The spectral index of the scalar density fluctuations, ns, is computed, and the result is consistent with the analysis of the Wilkinson-microwave anisotropy probe data. This model can lead to successful inflation with λ≈ 10-7, rather than 10-13 reported previously.
Noncommutative scalar field minimally coupled to nonsymmetric gravity
Energy Technology Data Exchange (ETDEWEB)
Kouadik, S.; Sefai, D. [Laboratory of Mechanic, Physics and Mathematical Modeling Medea University (Algeria)
2012-06-27
We construct a non-commutative non symmetric gravity minimally coupled model (the star product only couples matter). We introduce the action for the system considered namely a non-commutative scalar field propagating in a nontrivial gravitational background. We expand the action in powers of the anti-symmetric field and the graviton to second order adopting the assumption that the scalar is weekly coupled to the graviton. We compute the one loop radiative corrections to the self-energy of a scalar particle.
Cosmological spacetimes balanced by a scale covariant scalar field
Scholz, Erhard
2008-01-01
A scale invariant, Weyl geometric, Lagrangian approach to cosmology is explored, with a a scalar field \\phi of (scale) weight -1 as a crucial ingredient besides classical matter (Tann 1998, Drechsler 1999}. For a particularly simple class of Weyl geometric models (called Einstein-Weyl universes) the Klein-Gordon equation for \\phi is explicitly solvable. In this case the energy-stress tensor of the scalar field consists of a vacuum-like term \\Lambda g_{\\mu \
Supermassive black holes in scalar field galaxy halos
Ureña-López, L. Arturo; Liddle, Andrew R.
2002-01-01
Ultra-light scalar fields provide an interesting alternative to WIMPS as halo dark matter. In this paper we consider the effect of embedding a supermassive black hole within such a halo, and estimate the absorption probability and the accretion rate of dark matter onto the black hole. We show that the accretion rate would be small over the lifetime of a typical halo, and hence that supermassive central black holes can coexist with scalar field halos.
Associated single photons and doubly-charged scalars at linear - - colliders
Indian Academy of Sciences (India)
Biswarup Mukhopadhyaya; Santosh Kumar Rai
2007-11-01
Doubly-charged scalars, predicted in many models having exotic Higgs representations, can in general have lepton-number violating (LFV) couplings. We show that by using an associated monoenergetic final state photon seen at a future linear - - collider, we can have a clear and distinct signature for a doubly-charged resonance. The strength of the = 2 coupling can also be probed quite effectively as a function of the recoil mass of the doubly-charged scalar.
N-Body Simulations for Coupled Scalar Field Cosmology
Li, Baojiu
2010-01-01
We describe in detail the general methodology and numerical implementation of consistent N-body simulations for coupled scalar field cosmological models, including the background cosmology and the generation of initial conditions (with the different couplings to different matter species taken into account). We perform fully consistent simulations for a class of coupled scalar field models with an inverse power-law potential and negative coupling constant, for which the chameleon mechanism does not operate. We find that in such cosmological models the scalar-field potential plays a negligible role except in the background expansion, and the fifth force that is produced is proportional to gravity in magnitude, justifying the use of a rescaled gravitational constant G in some earlier N-body simulations of similar models. We study the effects of the scalar coupling on the nonlinear matter power spectra and compare with linear perturbation calculations to investigate where the nonlinear model deviates from the lin...
The singularity in supercritical collapse of a spherical scalar field
Burko, L M
1998-01-01
We study the singularity created in the supercritical collapse of a spherical massless scalar field. We first model the geometry and the scalar field to be homogeneous, and find a generic solution describing a spacelike singularity which is monotonic, scalar polynomial and strong. Next we confront the predictions of this analytical model with the pointwise behavior of fully-nonlinear and inhomogeneous numerical simulations, and find full compliance. We also study the phenomenology of the spatial structure of the singularity numerically. At asymptotically late advanced time the singularity approaches the Schwarzschild singularity, in addition to discrete points at finite advanced times, where the singularity is Schwarzschild-like. At other points the singularity is different from Schwarzschild due to the nonlinear scalar field.
Instability of a four-dimensional de Sitter black hole with a conformally coupled scalar field
Harper, Tom J. T.; Thomas, Paul A.; Winstanley, Elizabeth(Consortium for Fundamental Physics, School of Mathematics and Statistics, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH, United Kingdom); Young, Phil M.
2003-01-01
We study the stability of new neutral and electrically charged four-dimensional black hole solutions of Einstein's equations with a positive cosmological constant and conformally coupled scalar field. The neutral black holes are always unstable. The charged black holes are also shown analytically to be unstable for the vast majority of the parameter space of solutions, and we argue using numerical techniques that the configurations corresponding to the remainder of the parameter space are als...
Quark scalar, axial, and pseudoscalar charges in the Schwinger-Dyson formalism
Yamanaka, Nodoka; Imai, Shotaro; Doi, Takahiro M.; Suganuma, Hideo
2014-01-01
We calculate the scalar, axial, and pseudoscalar charges of the quark in the Schwinger-Dyson formalism of Landau gauge QCD. It is found that the dressed quark scalar density of the valence quark is significantly enhanced against the bare quark contribution, and the result explains qualitatively the phenomenologically known value of the pion-nucleon sigma term and also that given by lattice QCD. Moreover, we show that the Richardson's interquark potential suppresses the quark scalar density in...
Gauge Fields and Scalars in Rolling Tachyon Backgrounds
Mehen, Thomas; Wecht, Brian
2002-01-01
We investigate the dynamics of gauge and scalar fields on unstable D-branes with rolling tachyons. Assuming an FRW metric on the brane, we find a solution of the tachyon equation of motion which is valid for arbitrary tachyon potentials and scale factors. The equations of motion for a U(1) gauge field and a scalar field in this background are derived. These fields see an effective metric which differs from the original FRW metric. The field equations receive large corrections due to the curva...
Building a Holographic Superconductor with a Scalar Field Coupled Kinematically to Einstein Tensor
Kuang, Xiao-Mei
2016-01-01
We study the holographic dual description of a superconductor in which the gravity sector consists of a Maxwell field and a charged scalar field which except its minimal coupling to gravity it is also coupled kinematically to Einstein tensor. As the strength of the new coupling is increased, the critical temperature below which the scalar field condenses is lowering, the condensation gap decreases faster than the temperature, the width of the condensation gap is not proportional to the size of the condensate and at low temperatures the condensation gap tends to zero for the strong coupling. These effects which are the result of the presence of the coupling of the scalar field to the Einstein tensor in the gravity bulk, provide a dual description of impurities concentration in a superconducting state on the boundary.
Nonperturbative description of the thermal scalar effective potential at fixed charge
International Nuclear Information System (INIS)
Full text: Nowadays much attention is been devoted to the study of the phase transitions under extreme conditions, motivated mostly by the surge of experimental results from the heavy-ion experiments at the RHIC and at the LHC (Large Hadron Collider). Another important factor is the wide range of applications existing in systems where characteristic low energy phenomena may arise, such as in condensed matter, yet still possible to characterize through techniques used in quantum field theory, and going to the description of high energy systems, such as particles physics and cosmology. It is well known in the literature that conventional perturbative methods are not applicable in the description of phase transitions in general, since the perturbative expansion breaks at high temperature regimes or around the critical points, and non-perturbative methods are necessary to fully understand the phase transition phenomena in these different systems. In this work we perform a detailed study about the effects of including a fixed charge in the phase transition in a scalar field system, described by a charged scalar quantum field theory at finite temperature. The phase structure of the model is studied using a non-perturbative method know in the literature as Optimized Perturbation Theory (OPT) and we compare our results with earlier ones based on perturbation theory. (author)
Scalar field haloes as gravitational lenses
Schunck, F E; Mielke, E W
2006-01-01
A non-topological soliton model with a repulsive scalar self-interaction of the Emden type provides a constant density core,similarly as the empirical Burkert profile of dark matter haloes. As a further test, we derive the gravitational lens properties of our model, in particular, the demarcation curves between `weak' and `strong' lensing. Accordingly, strong lensing with typically three images is almost three times more probable for our solitonic model than for the Burkert fit. Moreover, some prospective consequences of a possible flattening of dark matter haloes are indicated.
The self-force on a non-minimally coupled static scalar charge outside a Schwarzschild black hole
Energy Technology Data Exchange (ETDEWEB)
Cho, Demian H J; Tsokaros, Antonios A; Wiseman, Alan G [Department of Physics, University of Wisconsin-Milwaukee, PO Box 413, Milwaukee, WI 53201 (United States)
2007-03-07
The finite part of the self-force on a static, non-minimally coupled scalar test charge outside a Schwarzschild black hole is zero. This result is determined from the work required to slowly raise or lower the charge through an infinitesimal distance. Unlike similar force calculations for minimally-coupled scalar charges or electric charges, we find that we must account for a flux of field energy that passes through the horizon and changes the mass and area of the black hole when the charge is displaced. This occurs even for an arbitrarily slow displacement of the non-minimally coupled scalar charge. For a positive coupling constant, the area of the hole increases when the charge is lowered and decreases when the charge is raised. The fact that the self-force vanishes for a static, non-minimally coupled scalar charge in Schwarzschild spacetime agrees with a simple prediction of the Quinn-Wald axioms. However, Zel'nikov and Frolov computed a non-vanishing self-force for a non-minimally coupled charge. Our method of calculation closely parallels the derivation of Zel'nikov and Frolov, and we show that their omission of this unusual flux is responsible for their (incorrect) result. When the flux is accounted for, the self-force vanishes. This correction eliminates a potential counter example to the Quinn-Wald axioms. The fact that the area of the black hole changes when the charge is displaced brings up two interesting questions that did not arise in similar calculations for static electric charges and minimally coupled scalar charges. (1) How can we reconcile a decrease in the area of the black hole horizon with the area theorem which concludes that {delta}Area{sub horizon} {>=} 0? The key hypothesis of the area theorem is that the stress-energy tensor must satisfy a null-energy condition T{sup {alpha}}{sup {beta}}l{sub {alpha}}l{sub {beta}} {>=} 0 for any null vector l{sub {alpha}}. We explicitly show that the stress-energy associated with a non
Higgs and gravitational scalar fields together induce Weyl gauge
Scholz, Erhard
2014-01-01
A common biquadratic potential for the Higgs field $h$ and an additional scalar field $\\phi$, non minimally coupled to gravity, is considered in locally scale symmetric approaches to standard model fields in curved spacetime. A common ground state of the two scalar fields exists and couples both fields to gravity, more precisely to scalar curvature $R$. In Einstein gauge ($\\phi = const$, often called "Einstein frame"), also $R$ is scaled to a constant. This condition makes perfect sense, even in the general case, in the Weyl geometric approach. There it has been called {\\em Weyl gauge}, because it was first considered by Weyl in the different context of his original scale geometric theory of gravity of 1918. Now it seems to get new meaning as a combined effect of electroweak theory and gravity, and their common influence on atomic frequencies.
Scalar field perturbations in Horava-Lifshitz cosmology
Wang, Anzhong; Maartens, Roy
2009-01-01
In this paper we study perturbations of a scalar field cosmology in Horava-Lifshitz gravity, adopting the Sotiriou-Visser-Weifurtner generalization, which is the most general setup without detailed balance but with the projectability condition. After obtaining the general field equations, including a sixth-order Klein-Gordon equation, we investigate scalar field perturbations coupled to gravity in a flat Friedmann-Robertson-Walker universe. In the sub-horizon regime, the metric and scalar field modes have independent oscillations with different frequencies and phases except in particular cases.On super-horizon scales the perturbations become adiabatic during slow-roll inflation driven by a single field and the comoving curvature perturbation is constant.
Thermodynamics of perfect fluids from scalar field theory
Ballesteros, Guillermo; Comelli, Denis; Pilo, Luigi
2016-07-01
The low-energy dynamics of relativistic continuous media is given by a shift-symmetric effective theory of four scalar fields. These scalars describe the embedding in spacetime of the medium and play the role of Stückelberg fields for spontaneously broken spatial and time translations. Perfect fluids are selected imposing a stronger symmetry group or reducing the field content to a single scalar. We explore the relation between the field theory description of perfect fluids to thermodynamics. By drawing the correspondence between the allowed operators at leading order in derivatives and the thermodynamic variables, we find that a complete thermodynamic picture requires the four Stückelberg fields. We show that thermodynamic stability plus the null-energy condition imply dynamical stability. We also argue that a consistent thermodynamic interpretation is not possible if any of the shift symmetries is explicitly broken.
Thermodynamics of perfect fluids from scalar field theory
Ballesteros, Guillermo; Pilo, Luigi
2016-01-01
The low-energy dynamics of relativistic continuous media is given by a shift-symmetric effective theory of four scalar fields. These scalars describe the embedding in spacetime of the medium and play the role of Stuckelberg fields for spontaneously broken spatial and time translations. Perfect fluids are selected imposing a stronger symmetry group or reducing the field content to a single scalar. We explore the relation between the field theory description of perfect fluids to thermodynamics. By drawing the correspondence between the allowed operators at leading order in derivatives and the thermodynamic variables, we find that a complete thermodynamic picture requires the four Stuckelberg fields. We show that thermodynamic stability plus the null energy condition imply dynamical stability. We also argue that a consistent thermodynamic interpretation is not possible if any of the shift symmetries is explicitly broken.
Li, Ran; Zhao, Junkun
2016-01-01
Reissner-Nordstr\\"om Anti-de Sitter (RNAdS) black holes are unstable against the charged scalar field perturbations due to the well-known superradiance phenomenon. We present the time domain analysis of charged scalar field perturbations in the RNAdS black hole background in general dimensions. We show that the instabilities of charged scalar field can be explicitly illustrated from the time profiles of evolving scalar field. By using the Prony method to fit the time evolution data, we confirm the mode that dominates the long time behavior of scalar field is in accordance with the quasinormal mode from the frequency domain analysis. The superradiance origin of the instability can also be demonstrated by comparing the real part of the dominant mode with the superradiant condition of charged scalar field. It is shown that all the unstable modes are superradiant, which is consistent with the analytical result in the frequency domain analysis. Furthermore, we also confirm there exists the rapid exponential growin...
Note on scalars, perfect fluids, constrained field theories, and all that
Diez-Tejedor, Alberto
2013-01-01
The relation of a scalar field with a perfect fluid has generated some debate along the last few years. In this paper we argue that shift-invariant scalar fields can describe accurately the potential flow of an isentropic perfect fluid, but, in general, the identification is possible only for a finite period of time. After that period in the evolution the dynamics of the scalar field and the perfect fluid branch off. The Lagrangian density for the velocity-potential can be read directly from the expression relating the pressure with the Taub charge and the entropy per particle in the fluid, whereas the other quantities of interest can be obtained from the thermodynamic relations.
Note on scalars, perfect fluids, constrained field theories, and all that
International Nuclear Information System (INIS)
The relation of a scalar field with a perfect fluid has generated some debate along the last few years. In this Letter we argue that shift-invariant scalar fields can describe accurately the potential flow of an isentropic perfect fluid, but, in general, the identification is possible only for a finite period of time. After that period in the evolution the dynamics of the scalar field and the perfect fluid branch off. The Lagrangian density for the velocity-potential can be read directly from the expression relating the pressure with the Taub charge and the entropy per particle in the fluid, whereas the other quantities of interest can be obtained from the thermodynamic relations
Quantum and classical aspects of scalar and vector fields around black holes
Wang, Mengjie
2016-01-01
This thesis presents recent studies on test scalar and vector fields around black holes. It is separated in two parts according to the asymptotic properties of the spacetime under study. In the first part, we investigate scalar and Proca fields on an asymptotically flat background. For the Proca field, we obtain a complete set of equations of motion in higher dimensional spherically symmetric backgrounds. These equations are solved numerically, both to compute Hawking radiation spectra and quasi-bound states. In the former case, we carry out a precise study of the longitudinal degrees of freedom induced by the field mass. This can be used to improve the model in the black hole event generators currently used at the Large Hadron Collider. Regarding quasi-bound states, we find arbitrarily long lived modes for a charged Proca field, as well as for a charged scalar field, in a Reissner-Nordstr\\"om black hole. The second part of this thesis presents research on superradiant instabilities of scalar and Maxwell fiel...
Inflation with an extra light scalar field after Planck
Vennin, Vincent; Koyama, Kazuya; Wands, David
2016-03-01
Bayesian inference techniques are used to investigate situations where an additional light scalar field is present during inflation and reheating. This includes (but is not limited to) curvaton-type models. We design a numerical pipeline where simeq 200 inflaton setups × 10 reheating scenarios = 2000 models are implemented and we present the results for a few prototypical potentials. We find that single-field models are remarkably robust under the introduction of light scalar degrees of freedom. Models that are ruled out at the single-field level are not improved in general, because good values of the spectral index and the tensor-to-scalar ratio can only be obtained for very fine-tuned values of the extra field parameters and/or when large non-Gaussianities are produced. The only exception is quartic large-field inflation, so that the best models after Planck are of two kinds: plateau potentials, regardless of whether an extra field is added or not, and quartic large-field inflation with an extra light scalar field, in some specific reheating scenarios. Using Bayesian complexity, we also find that more parameters are constrained for the models we study than for their single-field versions. This is because the added parameters not only contribute to the reheating kinematics but also to the cosmological perturbations themselves, to which the added field contributes. The interplay between these two effects lead to a suppression of degeneracies that is responsible for having more constrained parameters.
Quasistationary solutions of scalar fields around accreting black holes
Sanchis-Gual, Nicolas; Degollado, Juan Carlos; Izquierdo, Paula; Font, José A.; Montero, Pedro J.
2016-08-01
Massive scalar fields can form long-lived configurations around black holes. These configurations, dubbed quasibound states, have been studied both in the linear and nonlinear regimes. In this paper, we show that quasibound states can form in a dynamical scenario in which the mass of the black hole grows significantly due to the capture of infalling matter. We solve the Klein-Gordon equation numerically in spherical symmetry, mimicking the evolution of the spacetime through a sequence of analytic Schwarzschild black hole solutions of increasing mass. It is found that the frequency of oscillation of the quasibound states decreases as the mass of the black hole increases. In addition, accretion leads to an increase of the exponential decay of the scalar field energy. We compare the black hole mass growth rates used in our study with estimates from observational surveys and extrapolate our results to values of the scalar field masses consistent with models that propose scalar fields as dark matter in the universe. We show that, even for unrealistically large mass accretion rates, quasibound states around accreting black holes can survive for cosmological time scales. Our results provide further support to the intriguing possibility of the existence of dark matter halos based on (ultralight) scalar fields surrounding supermassive black holes in galactic centers.
Effective Action for Cosmological Scalar Fields at Finite Temperature
Cheung, Yeuk-Kwan E; Kang, Jin U; Kim, Jong Chol
2015-01-01
Scalar fields appear in many theories beyond the Standard Model of particle physics. In the early universe, they are exposed to extreme conditions, including high temperature and rapid cosmic expansion. Understanding their behavior in this environment is crucial to understand the implications for cosmology. We calculate the finite temperature effective action for the field expectation value in two particularly important cases, for damped oscillations near the ground state and for scalar fields with a flat potential. We find that the behavior in both cases can in good approximation be described by a complex valued effective potential that yields Markovian equations of motion. Near the potential minimum, we recover the solution to the well-known Langevin equation. For large field values we find a very different behavior, and our result for the damping coefficient significantly differs from the expressions given in the literature. We illustrate our results in a simple scalar model, for which we give analytic app...
Small scale structures in coupled scalar field dark matter
Directory of Open Access Journals (Sweden)
J. Beyer
2014-11-01
Full Text Available We investigate structure formation for ultra-light scalar field dark matter coupled to quintessence, in particular the cosmon–bolon system. The linear power spectrum is computed by a numerical solution of the coupled field equations. We infer the substructure abundance within a Milky Way-like halo. Estimates of dark halo abundances from recent galaxy surveys imply a lower bound on the bolon mass of about 9×10−22 eV. This seems to exclude a possible detection of scalar field dark matter through time variation in pulsar timing signals in the near future.
Higgs portal dark matter and neutrino mass and mixing with a doubly charged scalar
Hierro, I M; Rigolin, S
2016-01-01
We consider an extension of the Standard Model involving two new scalar particles around the TeV scale: a singlet neutral scalar $\\phi$, to be eventually identified as the Dark Matter candidate, plus a doubly charged $SU(2)_L$ singlet scalar, $S^{++}$, that can be the source for the non-vanishing neutrino masses and mixings. Assuming an unbroken $Z_2$ symmetry in the scalar sector, under which only the additional neutral scalar $\\phi$ is odd, we write the most general (renormalizable) scalar potential. The model may be regarded as a possible extension of the conventional Higgs portal Dark Matter scenario which also accounts for neutrino mass and mixing. This framework cannot completely explain the observed positron excess. However a softening of the discrepancy observed in conventional Higgs portal framework can be obtained, especially when the scale of new physics responsible for generating neutrino masses and lepton number violating processes is around 2 TeV.
Bose–Einstein condensates and scalar fields; exploring the similitudes
Energy Technology Data Exchange (ETDEWEB)
Castellanos, E. [Departamento de Física, Centro de Investigación y de Estudios Avanzados del IPN, A.P. 14-740, 07000 México D.F. (Mexico); Macías, A. [Departamento de Física, Universidad Autónoma Metropolitana-Iztapalapa, A.P. 55-534, México D.F. 09340 (Mexico); Núñez, D. [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior C.U., A.P. 70-543, México D.F. 04510 (Mexico)
2014-01-14
We analyze the the remarkable analogy between the classical Klein–Gordon equation for a test scalar field in a flat and also in a curved background, and the Gross–Pitaevskii equation for a Bose–Einstein condensate trapped by an external potential. We stress here that the solution associated with the Klein–Gordon equation (KG) in a flat space time has the same mathematical structure, under certain circumstances, to those obtained for the Gross–Pitaevskii equation, that is, a static soliton solution. Additionally, Thomas–Fermi approximation is applied to the 3–dimensional version of this equation, in order to calculate some thermodynamical properties of the system in curved a space–time back ground. Finally, we stress the fact that a gravitational background provides, in some cases, a kind of confining potential for the scalar field, allowing us to remarks even more the possible connection between scalar fields and the phenomenon of Bose–Einstein condensation.
DBI scalar field theory for QGP hydrodynamics
Nastase, Horatiu
2015-01-01
A way to describe the hydrodynamics of the quark-gluon plasma using a DBI action is proposed, based on the model found by Heisenberg for high energy scattering of nucleons. The expanding plasma is described as a shockwave in a DBI model for a real scalar standing in for the pion, and I show that one obtains a fluid description in terms of a relativistic fluid that near the shock is approximately ideal ($\\eta\\simeq 0$) and conformal. One can introduce an extra term inside the square root of the DBI action that generates a shear viscosity term in the energy-momentum tensor near the shock, as well as a bulk viscosity, and regulates the behaviour of the energy density at the shock, making it finite. The resulting fluid satisfies the relativistic Navier-Stokes equation with $u^\\mu, \\rho,P,\\eta$ defined in terms of $\\phi$ and its derivatives. One finds a relation between the parameters of the theory and the QGP thermodynamics, $\\a/\\b^2=\\eta/(sT)$, and by fixing $\\a$ and $\\b$ from usual (low multiplicity) particle s...
Irreducible Cartesian tensor expansions of scalar fields
International Nuclear Information System (INIS)
It is shown how a scalar function V(parallel R + Σ/sub i equals 1/sup n/ a/sub i/parallel) of a sum of n + 1 vectors can be expanded as a multiple Cartesian tensor series in the vectors a/ sub i/. This expansion is a rearrangement of the multiple Taylor series expansion of such a function. In order to prove the fundamental theorem, generalized Cartesian Legendre polynomials are defined. The theorem is applied to the eigenfunctions of the Laplace operator and to inverse powers. The expansion of the latter type of function leads to forms involving generalized hypergeometric functions in several variables. As a special case, the Cartesian form of the multipole expansion of the electrostatic potential between two linear molecules is derived. A number of sum rules for hypergeometric functions and addition formulas for (standard and modified) spherical Bessel functions are proved by using a reduction property of the generalized Legendre polynomials. The case of the expansion of a tensorial function is also briefly discussed
Boson Stars in a Theory of Complex Scalar Field coupled to Gravity
Kumar, Sanjeev; Kulshreshtha, Daya Shankar
2016-01-01
We study boson stars in a theory of complex scalar field coupled to Einstein gravity with the potential: $V(|\\Phi|) := m^{2} |\\Phi|^2 +2 \\lambda |\\Phi|$ (where $m^2$ and $\\lambda$ are positive constant parameters). This could be considered either as a theory of massive complex scalar field coupled to gravity in a conical potential or as a theory in the presence of a potential which is an overlap of a parabolic and a conical potential. We study our theory with positive as well as negative values of the cosmological constant $\\Lambda$. Boson stars are found to come in two types, having either ball-like or shell-like charge density. We have studied the properties of these solutions and have also determined their domains of existence for some specific values of the parameters of the theory. Similar solutions have also been obtained by Hartmann, Kleihaus, Kunz, and Schaffer, in a V-shaped scalar potential.
Dark energy parametrization motivated by scalar field dynamics
de la Macorra, Axel
2016-05-01
We propose a new dark energy (DE) parametrization motivated by the dynamics of a scalar field ϕ. We use an equation of state w parametrized in terms of two functions L and y, closely related to the dynamics of scalar fields, which is exact and has no approximation. By choosing an appropriate ansatz for L we obtain a wide class of behavior for the evolution of DE without the need to specify the scalar potential V. We parametrize L and y in terms of only four parameters, giving w a rich structure and allowing for a wide class of DE dynamics. Our w can either grow and later decrease, or it can happen the other way around; the steepness of the transition is not fixed and it contains the ansatz w={w}o+{w}a(1-a). Our parametrization follows closely the dynamics of a scalar field, and the function L allows us to connect it with the scalar potential V(φ ). While the Universe is accelerating and the slow roll approximation is valid, we get L≃ {({V}\\prime /V)}2. To determine the dynamics of DE we also calculate the background evolution and its perturbations, since they are important to discriminate between different DE models.
The dynamical behavior of scalar fields near the initial singularity
International Nuclear Information System (INIS)
One of the most important topics in present research on theoretical cosmology is the behavior of scalar fields in the very early universe, since by means of their existence it is possible to explain some of the basic phenomena that have characterized the evolution of the universe to its present state. Analyzing the Klein-Gordon equation in a homogeneous, isotropic and spatially flat universe model, the authors find the conditions for the existence of a universe dominated by a scalar field in its early stages
Braneworld inflation with a complex scalar field from Planck 2015
Mounzi, Z.; Ferricha-Alami, M.; Chakir, H.; Bennai, M.
2016-06-01
We study an inflationary model with a single complex scalar field in the framework of braneworld Randall-Sundrum model type 2. From the scalar curvature perturbation constrained by the recent observation values, and for specific choice of parameters, we can reduce the values of the coupling constant to take the natural values, and we found that the phase theta θ of the inflation field can take the narrow interval. We have also derived all known inflationary parameters (ns, r and dns/d ln (k)), which are widely consistent with the recent Planck data for a suitable choice of brane tension value λ.
Cosmological spacetimes balanced by a scale covariant scalar field
Scholz, Erhard
2008-01-01
A scale invariant, Weyl geometric, Lagrangian approach to cosmology is explored, with a a scalar field phi of (scale) weight -1 as a crucial ingredient besides classical matter \\cite{Tann:Diss,Drechsler:Higgs}. For a particularly simple class of Weyl geometric models (called {\\em Einstein-Weyl universes}) the Klein-Gordon equation for phi is explicitly solvable. In this case the energy-stress tensor of the scalar field consists of a vacuum-like term Lambda g_{mu nu} with variable coefficient ...
Dynamical Analysis of Scalar Field Cosmologies with Spatial Curvature
Gosenca, Mateja
2015-01-01
We explore the dynamical behaviour of cosmological models involving a scalar field (with an exponential potential and a canonical kinetic term) and a matter fluid with spatial curvature included in the equations of motion. Using appropriately defined parameters to describe the evolution of the scalar field energy in this situation, we find that there are two extra fixed points that are not present in the case without curvature. We also analyse the evolution of the effective equation-of-state parameter for different initial values of the curvature.
Langevin description of gauged scalar fields in a thermal bath
Miyamoto, Yuhei; Suyama, Teruaki; Yokoyama, Jun'ichi
2013-01-01
We study the dynamics of the oscillating gauged scalar field in a thermal bath. A Langevin type equation of motion of the scalar field, which contains both dissipation and fluctuation terms, is derived by using the real-time finite temperature effective action approach. The existence of the quantum fluctuation-dissipation relation between the non-local dissipation term and the Gaussian stochastic noise terms is verified. We find the noise variables are anti-correlated at equal-time. The dissipation rate for the each mode is also studied, which turns out to depend on the wavenumber.
Can a spectator scalar field enhance inflationary tensor mode?
Fujita, Tomohiro; Yokoyama, Shuichiro
2014-01-01
We consider the possibility of enhancing the inflationary tensor mode by introducing a spectator scalar field with a small sound speed which induces gravitational waves as a second order effect. We analytically obtain the power spectra of gravitational waves and curvature perturbation induced by the spectator scalar field. We found that the small sound speed amplifies the curvature perturbation much more than the tensor mode and the current observational constraint forces the induced gravitational waves to be negligible compared with those from the vacuum fluctuation during inflation.
Observational Constraints on New Exact Inflationary Scalar-field Solutions
Barrow, John D
2016-01-01
An algorithm is used to generate new solutions of the scalar field equations in homogeneous and isotropic universes. Solutions can be found for pure scalar fields with various potentials in the absence and presence of spatial curvature and other perfect fluids. A series of generalisations of the Chaplygin gas and bulk viscous cosmological solutions for inflationary universes are found. We also show how the Hubble slow-roll parameters can be calculated using the solution algorithm and we compare these inflationary solutions with the observational data provided by the Planck 2015 collaboration in order to constraint and rule out some of these models.
Effective field theory of modified gravity with two scalar fields: dark energy and dark matter
Gergely, László Á.; Tsujikawa, Shinji
2014-01-01
We present a framework for discussing the cosmology of dark energy and dark matter based on two scalar degrees of freedom. An effective field theory of cosmological perturbations is employed. A unitary gauge choice renders the dark energy field into the gravitational sector, for which we adopt a generic Lagrangian depending on three-dimensional geometrical scalar quantities arising in the ADM decomposition. We add to this dark-energy associated gravitational sector a scalar field $\\phi$ and i...
Effective action for scalar fields in two-dimensional gravity
International Nuclear Information System (INIS)
We consider a general two-dimensional gravity model minimally or nonminimally coupled to a scalar field. The canonical form of the model is elucidated, and a general solution of the equations of motion in the massless case is reviewed. In the presence of a scalar field all geometric fields (zweibein and Lorentz connection) are excluded from the model by solving exactly their Hamiltonian equations of motion. In this way the effective equations of motion and the corresponding effective action for a scalar field are obtained. It is written in a Minkowskian space-time and does not include any geometric variables. The effective action arises as a boundary term and is nontrivial both for open and closed universes. The reason is that unphysical degrees of freedom cannot be compactly supported because they must satisfy the constraint equation. As an example we consider spherically reduced gravity minimally coupled to a massless scalar field. The effective action is used to reproduce the Fisher and Roberts solutions
Quasiclassical approximation for ultralocal scalar fields
International Nuclear Information System (INIS)
It is shown how to obtain the quasiclassical evolution of a class of field theories called ultralocal fields. Coherent states that follow the 'classical' orbit as defined by Klauder's weak corespondence principle and restricted action principle is explicitly shown to approximate the quantum evolutions as (h/2π) → o. (Author)
The asymptotic safety scenario and scalar field inflation
Rahmede, Christoph
2013-01-01
We study quantum gravity corrections to early universe cosmology as resulting within the asymptotic safety scenario. We analyse if it is possible to obtain accelerated expansion in the regime of the renormalisation group fixed point in a theory with Einstein-Hilbert gravity and a scalar field. We show how this phase impacts cosmological perturbations observed in the cosmic microwave background.
Scalar fields and cosmic censorship hypothesis in general relativity
International Nuclear Information System (INIS)
We discuss an influence of the presence of some nonstandard scalar fields in the vicinity of naked time-like singularity on the type and properties of this singularity. The main goal is to study the validity of the Penrose's Cosmic Censorship hypothesis in the General Relativity
Gravitational collapse of massless scalar field and cosmic censorship
International Nuclear Information System (INIS)
We present a numerical study of the gravitational collapse of a massless scalar field. We calculate the future evolution of new initial data, suggested by Christodoulou, and we show that in spite of the original expectations these data lead only to singularities engulfed by an event horizon
Brane Structure from Scalar Field in Warped Spacetime
Bazeia, D; Gomes, A R
2004-01-01
We deal with scalar field coupled to gravity in five dimensions in warped geometry. We investigate models described by potentials that drive the system to support thick brane solutions that engender internal structure. We also show that the brane solutions simulate the occurrence of the complete wetting phenomenon at high temperatures.
Scalar fields in the late Universe: The mechanical approach
Burgazli, Alvina; Morais, João; Kumar, K Sravan
2015-01-01
In this paper, we consider the Universe at the late stage of its evolution and deep inside the cell of uniformity. At these scales, we consider the Universe to be filled with dust-like matter in the form of discretely distributed galaxies, a minimal scalar field, the cosmological constant and radiation as matter sources. We investigate such a Universe in the mechanical approach. This means that the peculiar velocities of the inhomogeneities (in the form of galaxies) as well as fluctuations of other perfect fluids are non-relativistic. Under such conditions, we investigate the theory of scalar perturbations. We show that, at the background level, the considered scalar field has a constant equation of state (EoS) parameter $w=-1/3$. The fluctuations of the energy density and pressure of this field are defined by the interaction between scalar field background and the gravitational potential of the system. These fluctuations are concentrated around the galaxies screening their gravitational potentials. The expre...
Scalar field entanglement entropy for small Schwarzschild black hole
Teslyk, Maksym; Teslyk, Olena
2013-01-01
We consider scalar field entanglement entropy generated with black hole of (sub)planck mass scale thus implying the unitary evolution of gravity. The dependence on the dimension of the Hilbert space for degrees of freedom located behind the horizon is taken into account. The obtained results contain polylogarithmic terms.
Effective action for a quantum scalar field in warped spaces
Energy Technology Data Exchange (ETDEWEB)
Hoff da Silva, J.M.; Mendonca, E.L.; Scatena, E. [Universidade Estadual Paulista ' ' Julio de Mesquita Filho' ' -UNESP, Departamento de Fisica e Quimica, Guaratingueta, SP (Brazil)
2015-11-15
We investigate the one-loop corrections, at zero as well as finite temperature, of a scalar field taking place in a braneworld motivated warped background. After to reach a well-defined problem, we calculate the effective action with the corresponding quantum corrections to each case. (orig.)
Vacuum polarization by a massive scalar field in Schwarzschild spacetime
International Nuclear Information System (INIS)
The vacuum polarization by massive scalar particles in the gravitational field of the Schwarzschild black hole is discussed. The explicit expression for the vacuum energy-momentum tensor is obtained in the case when the Compton length lambdasub(m)=h/mc of the massive particle is much less than the gravitational radius of a black hole. (orig.)
Effects of a scalar scaling field on quantum mechanics
Benioff, Paul
2016-07-01
This paper describes the effects of a complex scalar scaling field on quantum mechanics. The field origin is an extension of the gauge freedom for basis choice in gauge theories to the underlying scalar field. The extension is based on the idea that the value of a number at one space time point does not determine the value at another point. This, combined with the description of mathematical systems as structures of different types, results in the presence of separate number fields and vector spaces as structures, at different space time locations. Complex number structures and vector spaces at each location are scaled by a complex space time dependent scaling factor. The effect of this scaling factor on several physical and geometric quantities has been described in other work. Here the emphasis is on quantum mechanics of one and two particles, their states and properties. Multiparticle states are also briefly described. The effect shows as a complex, nonunitary, scalar field connection on a fiber bundle description of nonrelativistic quantum mechanics. The lack of physical evidence for the presence of this field so far means that the coupling constant of this field to fermions is very small. It also means that the gradient of the field must be very small in a local region of cosmological space and time. Outside this region, there are no restrictions on the field gradient.
Effects of a scalar scaling field on quantum mechanics
Benioff, Paul
2016-04-01
This paper describes the effects of a complex scalar scaling field on quantum mechanics. The field origin is an extension of the gauge freedom for basis choice in gauge theories to the underlying scalar field. The extension is based on the idea that the value of a number at one space time point does not determine the value at another point. This, combined with the description of mathematical systems as structures of different types, results in the presence of separate number fields and vector spaces as structures, at different space time locations. Complex number structures and vector spaces at each location are scaled by a complex space time dependent scaling factor. The effect of this scaling factor on several physical and geometric quantities has been described in other work. Here the emphasis is on quantum mechanics of one and two particles, their states and properties. Multiparticle states are also briefly described. The effect shows as a complex, nonunitary, scalar field connection on a fiber bundle description of nonrelativistic quantum mechanics. The lack of physical evidence for the presence of this field so far means that the coupling constant of this field to fermions is very small. It also means that the gradient of the field must be very small in a local region of cosmological space and time. Outside this region, there are no restrictions on the field gradient.
Exact Inflationary Solution in String-Motivated Scalar Field Cosmology
Institute of Scientific and Technical Information of China (English)
王文福
2001-01-01
We present a new exact solution to Einstein's equations that describes the evolution of inflationary universe models. The inflation is driven by the evolution of a scalar field with an approximate two-loop four-dimensional string potential. In this scenario, the inflation began immediately after the epoch governed by quantum gravity and therefore there is no initial singularity. The successful inflation scenario is expected to appear only at two loop order. For a1/｜a2｜ ≥ 90, the spectral index ns of the scalar density fluctuations lies well inside the limits set by the cosmic background explorer satellite and the gravitational wave spectral index is ng≈1.
Scalar field quasinormal frequencies of Reissner-Nordstr\\"om black hole surrounded by quintessence
Wu, Chen
2016-01-01
We evaluate the quasinormal modes of massless scalar field around Reissner-Nordstr$\\ddot{\\text{o}}$m black hole surrounded by a static and spherically symmetric quintessence by using the continued fraction method. The appropriate Frobenius series for three special cases of the quintessence parameter $ \\epsilon = -1/3, -2/3$ and $-1$ are derived successfully. We show that the variation of quasinormal frequencies with charge of the black hole and the quintessential parameters. The numerical res...
Tunnelling of scalar and Dirac particles from squashed charged rotating Kaluza-Klein black holes
Stetsko, M M
2014-01-01
Thermal radiation of scalar particles and Dirac fermions from squashed charged rotating five-dimensional black holes is considered. To obtain temperature of the black holes we use the tunnelling method. In case of scalar particles we make use of the Hamilton-Jacobi equation. To consider tunnelling of fermions the Dirac equation was investigated. The examination shows that radial parts of the action for scalar particles and fermions in quasi-classical limit in the vicinity of horizon are almost the same and as a consequence it gives rise to the identical expressions for the temperature in both cases.
Tunnelling of scalar and Dirac particles from squashed charged rotating Kaluza-Klein black holes
Stetsko, M. M.
2016-02-01
The thermal radiation of scalar particles and Dirac fermions from squashed charged rotating five-dimensional black holes is considered. To obtain the temperature of the black holes we use the tunnelling method. In the case of scalar particles we make use of the Hamilton-Jacobi equation. To consider tunnelling of fermions the Dirac equation was investigated. The examination shows that the radial parts of the action for scalar particles and fermions in the quasi-classical limit in the vicinity of horizon are almost the same and as a consequence it gives rise to identical expressions for the temperature in the two cases.
Tunnelling of scalar and Dirac particles from squashed charged rotating Kaluza-Klein black holes
Energy Technology Data Exchange (ETDEWEB)
Stetsko, M.M. [Ivan Franko National University of Lviv, Department of Theoretical Physics, Lviv (Ukraine)
2016-02-15
The thermal radiation of scalar particles and Dirac fermions from squashed charged rotating five-dimensional black holes is considered. To obtain the temperature of the black holes we use the tunnelling method. In the case of scalar particles we make use of the Hamilton-Jacobi equation. To consider tunnelling of fermions the Dirac equation was investigated. The examination shows that the radial parts of the action for scalar particles and fermions in the quasi-classical limit in the vicinity of horizon are almost the same and as a consequence it gives rise to identical expressions for the temperature in the two cases. (orig.)
Exploring the thermodynamics of noncommutative scalar fields
Brito, Francisco A.; Lima, Elisama E. M.
2016-04-01
We study the thermodynamic properties of the Bose-Einstein condensate (BEC) in the context of the quantum field theory with noncommutative target space. Our main goal is to investigate in which temperature and/or energy regimes the noncommutativity can characterize some influence on the BEC properties described by a relativistic massive noncommutative boson gas. The noncommutativity parameters play a key role in the modified dispersion relations of the noncommutative fields, leading to a new phenomenology. We have obtained the condensate fraction, internal energy, pressure and specific heat of the system and taken ultrarelativistic (UR) and nonrelativistic (NR) limits. The noncommutative effects on the thermodynamic properties of the system are discussed. We found that there appear interesting signatures around the critical temperature.
Electromagnetic fields with vanishing scalar invariants
Czech Academy of Sciences Publication Activity Database
Ortaggio, Marcello; Pravda, Vojtěch
2016-01-01
Roč. 33, č. 11 (2016), s. 115010. ISSN 0264-9381 R&D Projects: GA ČR GA13-10042S Institutional support: RVO:67985840 Keywords : electromagnetic fields * n-dimensional spacetime * Einstein-Maxwell equations Subject RIV: BA - General Mathematics Impact factor: 3.168, year: 2014 http://dx.doi.org/10.1088/0264-9381/33/11/115010
Scalar field localization on deformed extra space
Energy Technology Data Exchange (ETDEWEB)
Rubin, Sergey G. [National Research Nuclear University ' ' MEPhI' ' (Moscow Engineering Physics Institute), Moscow (Russian Federation)
2015-07-15
Field localization on 2-dim extra space is considered in the framework of f(R) gravity. It is shown that interference of the local matter energy distribution and the metric of the extra space forms a point-like defect - a 4-dim brane. The energy-momentum of the brane depends on the initial conditions, which could lead to an arbitrarily small cosmological Λ term. (orig.)
Inflation with an extra light scalar field after Planck
Vennin, Vincent; Wands, David
2015-01-01
Bayesian inference techniques are used to investigate situations where an additional light scalar field is present during inflation and reheating. This includes (but is not limited to) curvaton-type models. We design a numerical pipeline where $\\simeq 200$ inflaton setups $\\times\\, 10$ reheating scenarios $= 2000$ models are implemented and we present the results for a few prototypical potentials. We find that single-field models are remarkably robust under the introduction of light scalar degrees of freedom. Models that are ruled out at the single-field level are not improved in general, because good values of the spectral index and the tensor-to-scalar ratio can only be obtained for very fine-tuned values of the extra field parameters and/or when large non-Gaussianities are produced. The only exception is quartic large-field inflation, so that the best models after Planck are of two kinds: plateau potentials, regardless of whether an extra field is added or not, and quartic large-field inflation with an ext...
The fluctuation-dissipation dynamics of cosmological scalar fields
Bartrum, Sam; Rosa, Joao G
2014-01-01
We show that dissipative effects have a significant impact on the evolution of cosmological scalar fields, leading to friction, entropy production and field fluctuations. We explicitly compute the dissipation coefficient for different scalar fields within the Standard Model and some of its most widely considered extensions, in different parametric regimes. We describe the generic consequences of fluctuation-dissipation dynamics in the post-inflationary universe and analyze in detail two important effects. Firstly, we show that dissipative friction delays the process of spontaneous symmetry breaking and may even damp the the motion of a Higgs field sufficiently to induce a late period of warm inflation. Along with dissipative entropy production, this may parametrically dilute the abundance of dangerous thermal relics. Secondly, we show that dissipation can generate the observed baryon asymmetry without symmetry restoration, and we develop in detail a model of dissipative leptogenesis. We further show that this...
Sensitivity of atom interferometry to ultralight scalar field dark matter
Geraci, Andrew A.; Derevianko, Andrei
2016-01-01
We discuss the use of atom interferometry as a tool to search for Dark Matter (DM) composed of ultra-light scalar fields. Previous work on ultra-light DM detection using accelerometers has considered the possibility of equivalence principle violating effects whereby gradients in the dark matter field can directly produce relative accelerations between media of differing composition. In atom interferometers, we find that time-varying phase signals from oscillatory, or dilaton-like, DM can also...
General features of single-scalar field dark energy models
Perenon, Louis
2016-01-01
We present a systematic study of modified gravity (MG) models containing a single scalar field non-minimally coupled to the metric. Despite a large parameter space, exploiting the effective field theory of dark energy (EFT of DE) formulation and imposing simple physical constraints such as stability conditions and (sub-)luminal propagation of perturbations, we arrive at a number of generic predictions about the large scale structures.
On the stability of the asymptotically free scalar field theories
International Nuclear Information System (INIS)
Asymptotic freedom plays a vital role in our understanding of the theory of particle interactions. To have this property, one has to resort to a Non-abelian gauge theory with the number of colors equal to or greater than three (QCD). However, recent studies have shown that simple scalar field theories can possess this interesting property. These theories have non-Hermitian effective field forms but their classical potentials are bounded from above. In this work, we shall address the stability of the vacua of the bounded from above (−Φ4+n) scalar field theories. Moreover, we shall cover the effect of the distribution of the Stokes wedges in the complex Φ-plane on the features of the vacuum condensate within these theories
A Note on Scalar Field Theory in AdS_3/CFT_2
Minces, Pablo
2009-01-01
We consider a scalar field theory in AdS_{d+1}, and introduce a formalism on surfaces at equal values of the radial coordinate. In particular, we define the corresponding conjugate momentum. We compute the Noether currents for isometries in the bulk, and carefully perform the asymptotic limit on the corresponding `conserved' charges. We then introduce Poisson brackets at the border, and show that the asymptotic values of the bulk scalar field and the conjugate momentum transform as conformal fields of scaling dimensions \\Delta_{-} and \\Delta_{+}, respectively, where \\Delta_{\\pm} are the standard parameters giving the asymptotic behavior of the scalar field in AdS. Then we consider the case d=2, where the boundary is described in terms of complex holomorphic and antiholomorphic coordinates. We obtain two copies of the Virasoro algebra, with vanishing central charge. An AdS_3/CFT_2 prescription, giving the commutators of the boundary CFT in terms of the Poisson brackets at the border, arises in a natural way. W...
A study of phantom scalar field cosmology using Lie and Noether symmetries
Dutta, Sourav
2016-01-01
The paper deals with phantom scalar field cosmology in Einstein gravity. At first using Lie symmetry, the coupling function to the kinetic term and the potential function of the scalar field and the equation of state parameter of the matter field are determined and a simple solution is obtained. Subsequently, Noether symmetry is imposed on the Lagrangian of the system. The symmetry vector is obtained and the potential takes a very general form from which potential using Lie Symmetry can be obtained as a particular case. Then we choose a point transformation $(a,\\phi)\\rightarrow(u,v)$ such that one of the transformed variables (say u) is a cyclic for the Lagrangian. Using conserved charge (corresponding to the cyclic coordinate) and the constant of motion, solutions are obtained.
Institute of Scientific and Technical Information of China (English)
陈光
2001-01-01
The static spherically symmetric solution of Einstein gravity coupled to electromagnetic and scalar fields is obtained under the consideration of the self-gravitational interaction of the electromagnetic and scalar fields, which is singularityfree and stable.
New techniques in 3D scalar and vector field visualization
International Nuclear Information System (INIS)
At Lawrence Livermore National Laboratory (LLNL) we have recently developed several techniques for volume visualization of scalar and vector fields, all of which use back-to-front compositing. The first renders volume density clouds by compositing polyhedral volume cells or their faces. The second is a ''splatting'' scheme which composites textures used to reconstruct the scalar or vector fields. One version calculates the necessary texture values in software, and another takes advantage of hardware texture mapping. The next technique renders contour surface polygons using semi-transparent textures, which adjust appropriately when the surfaces deform in a flow, or change topology. The final one renders the ''flow volume'' of smoke or dye tracer swept out by a fluid flowing through a small generating polygon. All of these techniques are applied to a climate model data set, to visualize cloud density and wind velocity
Constraining scalar field dark energy with cosmological observations
Samushia, Lado
2009-01-01
High precision cosmological observations in last decade suggest that about 70% of our universe's energy density is in so called "Dark Energy" (DE). Observations show that DE has negative effective pressure and therefore unlike conventional energy sources accelerates the cosmic expansion instead of decelerating it. DE is highly uniform and has become a dominant component only recently. The simplest candidate for DE is the time-independent cosmological constant $\\Lambda$. Although successful in fitting available data, the cosmological constant model has a number of theoretical shortcomings and because of that alternative models of DE are considered. In one such scenario a cosmological scalar field that slowly rolls down its potential acts like a time-dependent cosmological constant. I have used different independent cosmological data sets to constrain the time dependence of DE's energy density in the framework of the slowly-rolling cosmological scalar field model. Present data favors a time-independent cosmolog...
The scalar field in quantum gravity: a spin foam model
International Nuclear Information System (INIS)
Spin foams are nonperturbative models that describe spacetime at the Planck scale. They have been introduced starting from loop quantum gravity, but have consequently been recognized in other approaches. The most prominent of all is the Barrett-Crane model. However, this is a description of pure gravity and various attempts have been made in order to introduce matter in this general setting. The present paper describes the coupling of a massless scalar field to the Riemannian Barrett-Crane model and is, to our best knowledge, the first attempt of this kind. The main result is the computation of the partition function for the coupled model. This exhibits the general structure of a spin foam partition function. It is given by a product of face, edge and vertex amplitudes together with a sum over the irreducible representations of both the gauge group of the scalar field and the gauge group of gravity. (author)
Scalar Field Cosmologies Hidden Within the Nonlinear Schrodinger Equation
Lidsey, James E
2013-01-01
The nonlinear, cubic Schrodinger (NLS) equation has numerous physical applications, but in general is very difficult to solve. Nonetheless, under certain circumstances parameters quantifying the width, momentum and energy of the wavefunction evolve under a closed set of ordinary differential equations. It is shown that for the case of the radial, two dimensional NLS equation, such evolution equations may be mapped directly onto the cosmological Friedmann equations for a spatially flat and isotropic universe sourced by a self-interacting scalar field and a barotropic perfect fluid. Consequently, analytical techniques that have been developed to study the dynamics of such cosmological models may be applied to gain insight into aspects of nonlinear quantum mechanics. In this paper, the Hamilton-Jacobi formalism of the Friedmann equations, where the scalar field is viewed as the dynamical variable, is developed within this context. Algorithms for finding exact solutions are presented and the scaling solutions det...
Scalar field as a Bose-Einstein condensate?
International Nuclear Information System (INIS)
We discuss the analogy between a classical scalar field with a self-interacting potential, in a curved spacetime described by a quasi-bounded state, and a trapped Bose-Einstein condensate. In this context, we compare the Klein-Gordon equation with the Gross-Pitaevskii equation. Moreover, the introduction of a curved background spacetime endows, in a natural way, an equivalence to the Gross-Pitaevskii equation with an explicit confinement potential. The curvature also induces a position dependent self-interaction parameter. We exploit this analogy by means of the Thomas-Fermi approximation, commonly used to describe the Bose-Einstein condensate, in order to analyze the quasi bound scalar field distribution surrounding a black hole
Scalar field as a Bose-Einstein condensate?
Energy Technology Data Exchange (ETDEWEB)
Castellanos, Elías; Escamilla-Rivera, Celia [Mesoamerican Centre for Theoretical Physics (ICTP regional headquarters in Central America, the Caribbean and Mexico), Universidad Autónoma de Chiapas, Carretera Zapata Km. 4, Real del Bosque (Terán), 29040, Tuxtla Gutiérrez, Chiapas (Mexico); Macías, Alfredo [Departamento de Física, Universidad Autónoma Metropolitana-Iztapalapa, A.P. 55-534, Mexico D.F. 09340 (Mexico); Núñez, Darío, E-mail: ecastellanos@mctp.mx, E-mail: cescamilla@mctp.mx, E-mail: amac@xanum.uam.mx, E-mail: nunez@nucleares.unam.mx [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior C.U., A.P. 70-543, México D.F. 04510 (Mexico)
2014-11-01
We discuss the analogy between a classical scalar field with a self-interacting potential, in a curved spacetime described by a quasi-bounded state, and a trapped Bose-Einstein condensate. In this context, we compare the Klein-Gordon equation with the Gross-Pitaevskii equation. Moreover, the introduction of a curved background spacetime endows, in a natural way, an equivalence to the Gross-Pitaevskii equation with an explicit confinement potential. The curvature also induces a position dependent self-interaction parameter. We exploit this analogy by means of the Thomas-Fermi approximation, commonly used to describe the Bose-Einstein condensate, in order to analyze the quasi bound scalar field distribution surrounding a black hole.
LHC bounds on lepton number violation mediated by doubly and singly-charged scalars
International Nuclear Information System (INIS)
The only possible doubly-charged scalar decays into two Standard Model particles are into pairs of same-sign charged leptons, H±±→l±l±,l=e,μ,τ, or gauge bosons, H±±→W±W±; being necessary the observation of both to assert the violation of lepton number. However, present ATLAS and CMS limits on doubly-charged scalar production are obtained under specific assumptions on its branching fractions into dileptons only. Although they can be extended to include decays into dibosons and lepton number violating processes. Moreover, the production rates also depend on the type of electroweak multiplet H±± belongs to. We classify the possible alternatives and provide the Feynman rules and codes for generating the corresponding signals for pair and associated doubly-charged scalar production, including the leading contribution from the s-channel exchange of electroweak gauge bosons as well as the vector-boson fusion corrections. Then, using the same analysis criteria as the LHC collaborations we estimate the limits on the H±± mass as a function of the electroweak multiplet it belongs to, and obtain the bounds on the lepton number violating processes pp→H±±H∓∓→ℓ±ℓ±W∓W∓ and pp→H±±H∓→ℓ±ℓ±W∓Z, ℓ=e,μ, implied by the ATLAS and CMS doubly-charged scalar searches
Light-front Quantized Scalar Field Theory and Phase Transition
Srivastava, Prem P.
1994-01-01
The light-front Hamiltonian formulation for the scalar field theory contains a new ingredient in the form of a constraint equation. Renormalization of the two dimensional $\\phi^{4}$ theory, described in the continuum, is discussed. The mass renormalization condition and the renormalized constraint equation contain all the information to describe the phase transition in the theory, which is found to be of the second order. We argue that the same result would also be obtained in the conventiona...
Coupled dark energy: a dynamical analysis with complex scalar field
Landim, Ricardo C G
2016-01-01
The dynamical analysis for coupled dark energy with dark matter is presented, where a complex scalar field is taken into account and it is considered in the presence of a barothropic fluid. We consider three dark energy candidates: quintessence, phantom and tachyon. The critical points are found and their stabilities analyzed, leading to the three cosmological eras (radiation, matter and dark energy), for a generic potential. The results presented here enlarge the previous analyses found in the literature.
Coupled dark energy: a dynamical analysis with complex scalar field
Landim, Ricardo C. G.
2016-01-01
The dynamical analysis for coupled dark energy with dark matter is presented, where a complex scalar field is taken into account and it is considered in the presence of a barothropic fluid. We consider three dark-energy candidates: quintessence, phantom, and tachyon. The critical points are found and their stabilities analyzed, leading to the three cosmological eras (radiation, matter, and dark energy), for a generic potential. The results presented here extend the previous analyses found in ...
Higgs particles interacting via a scalar Dark Matter field
Bhattacharya, Yajnavalkya; Darewych, Jurij W.
2016-01-01
We study a system of two Higgs bound state, interacting via a real scalar Dark Matter mediating field, without imposing $Z_2$ symmetry on the DM sector of the postulated Lagrangian. The variational method in the Hamiltonian formalism of QFT is used to derive relativistic wave equations for the two-Higgs system, using a truncated Fock-space trial state. Approximate solutions of the 2-body relativistic coupled integral equations are presented, and conditions for the existence of Higgs bound sta...
Scalar fields in BTZ black hole spacetime and entanglement entropy
Veer Singh, Dharm; Siwach, Sanjay
2013-12-01
We study the quantum scalar fields in the background of BTZ black hole spacetime. We calculate the entanglement entropy using the discretized model, which resembles a system of coupled harmonic oscillators. The leading term of the entropy formula is standard Bakenstein-Hawking entropy and sub-leading corresponds to quantum corrections to black hole entropy. We calculate the coefficient of sub-leading logarithmic corrections numerically.
Non-trivial fixed points of the scalar field theory
International Nuclear Information System (INIS)
The phase structure of the scalar field theory with arbitrary powers of the gradient operator and a local non-analytic potential is investigated by the help of the RG in Euclidean space. Infinitely many nontrivial fixed points of the RG transformations are found. The corresponding effective actions are unbounded from below and probably do not exhibit any particle content. Therefore they do not provide physically sensible theories. (author)
Higgs particles interacting via a scalar Dark Matter field
Directory of Open Access Journals (Sweden)
Bhattacharya Yajnavalkya
2016-01-01
Full Text Available We study a system of two Higgs particles, interacting via a scalar Dark Matter mediating field. The variational method in the Hamiltonian formalism of QFT is used to derive relativistic wave equations for the two-Higgs system, using a truncated Fock-space trial state. Approximate solutions of the two-body equations are used to examine the existence of Higgs bound states.
Hydrodynamic Transport Coefficients in Relativistic Scalar Field Theory
Jeon, Sangyong
1994-01-01
Hydrodynamic transport coefficients may be evaluated from first principles in a weakly coupled scalar field theory at arbitrary temperature. In a theory with cubic and quartic interactions, the infinite class of diagrams which contribute to the leading weak coupling behavior are identified and summed. The resulting expression may be reduced to a single linear integral equation, which is shown to be identical to the corresponding result obtained from a linearized Boltzmann equation describing ...
A non-associative quaternion scalar field theory
Giardino, Sergio
2012-01-01
A non-associative Groenewold-Moyal plane is constructed using quaternion-valued function algebras. The symmetrized multi-particle states, the scalar product, the annihilation/creation algebra and d the formulation in terms of a Hopf algebra are also developed. Non-associative quantum algebras in terms of position and momentum operators are given as the simplest examples of a framework whose applications may involve string theory and non-linear quantum field theory
Coupled dark energy: a dynamical analysis with complex scalar field
Energy Technology Data Exchange (ETDEWEB)
Landim, Ricardo C.G. [Universidade de Sao Paulo, Instituto de Fisica, Caixa Postal 66318, Sao Paulo, SP (Brazil)
2016-01-15
The dynamical analysis for coupled dark energy with dark matter is presented, where a complex scalar field is taken into account and it is considered in the presence of a barothropic fluid. We consider three dark-energy candidates: quintessence, phantom, and tachyon. The critical points are found and their stabilities analyzed, leading to the three cosmological eras (radiation, matter, and dark energy), for a generic potential. The results presented here extend the previous analyses found in the literature. (orig.)
Coupled dark energy: a dynamical analysis with complex scalar field
International Nuclear Information System (INIS)
The dynamical analysis for coupled dark energy with dark matter is presented, where a complex scalar field is taken into account and it is considered in the presence of a barothropic fluid. We consider three dark-energy candidates: quintessence, phantom, and tachyon. The critical points are found and their stabilities analyzed, leading to the three cosmological eras (radiation, matter, and dark energy), for a generic potential. The results presented here extend the previous analyses found in the literature. (orig.)
Study of Inflationary Generalized Cosmic Chaplygin Gas for Standard and Tachyon Scalar Fields
Sharif, M
2014-01-01
We consider an inflationary universe model in the context of generalized cosmic Chaplygin gas by taking matter field as standard and tachyon scalar fields. We evaluate the corresponding scalar fields and scalar potentials during intermediate and logamediate inflationary regimes by modifying the first Friedmann equation. In each case, we evaluate the number of e-folds, scalar as well as tensor power spectra, scalar spectral index and important observational parameter, i.e., tensor-scalar ratio in terms of inflatons. The graphical behavior of this parameter shows that the model remains incompatible with WMAP7 and Planck observational data in each case.
Study of inflationary generalized cosmic Chaplygin gas for standard and tachyon scalar fields
Energy Technology Data Exchange (ETDEWEB)
Sharif, M.; Saleem, Rabia [University of the Punjab, Department of Mathematics, Lahore (Pakistan)
2014-07-15
We consider an inflationary universe model in the context of the generalized cosmic Chaplygin gas by taking the matter field as standard and tachyon scalar fields. We evaluate the corresponding scalar fields and scalar potentials during the intermediate and logamediate inflationary regimes by modifying the first Friedmann equation. In each case, we evaluate the number of e-folds, scalar as well as tensor power spectra, scalar spectral index, and the important observational parameter, the tensor-scalar ratio in terms of inflation. The graphical behavior of this parameter shows that the model remains incompatible with WMAP7 and Planck observational data in each case. (orig.)
On the Energy-Momentum Tensor of the Scalar Field in Scalar--Tensor Theories of Gravity
Santiago, David I.; Silbergleit, Alexander S.
1999-01-01
We study the dynamical description of gravity, the appropriate definition of the scalar field energy-momentum tensor, and the interrelation between them in scalar-tensor theories of gravity. We show that the quantity which one would naively identify as the energy-momentum tensor of the scalar field is not appropriate because it is spoiled by a part of the dynamical description of gravity. A new connection can be defined in terms of which the full dynamical description of gravity is explicit, ...
Production of Charged Scalars from the Littlest Higgs Model Associated with Top Quark at LHC
Institute of Scientific and Technical Information of China (English)
LIU Wei-Na; LIU Yao-Bei; LI Ping; SHEN Jie-Fen; GOU Qing-Quan; CUI Xiao-Min; ZHAO Yan-Ping; REN Xiao-Yan
2008-01-01
The littlest Higgs (LH) model is the most economical one among various little Higgs models, which predicts the existence of the charged scalars φ±. In this paper, we study the production of the charged Higgs boson φ- with single top quark via the process gb → tφ- at the CERN Large Hadron Collider (LHC). The numerical results show that the production cross section is smaller than 0.2 pb in most of the parameters space, it is very difficult to observe the signatures of the charged scalars via the process pp → gb + X → tφ- + X at the LHC experiments. However, it can open a window to distinguish the top-pions in the TC2 model or charged Higgs in the MSSM from φ±.
Synthesis of magnetic systems producing field with maximal scalar characteristics
International Nuclear Information System (INIS)
A method of synthesis of the magnetic systems (MSs) consisting of uniformly magnetized blocks is proposed. This method allows to synthesize MSs providing maximum value of any magnetic field scalar characteristic. In particular, it is possible to synthesize the MSs providing the maximum of a field projection on a given vector, a gradient of a field modulus and a gradient of a field energy on a given directing vector, a field magnitude, a magnetic flux through a given surface, a scalar product of a field or a force by a directing function given in some area of space, etc. The synthesized MSs provide maximal efficiency of permanent magnets utilization. The usage of the proposed method of MSs synthesis allows to change a procedure of projecting in principal, namely, to execute it according to the following scheme: (a) to choose the sizes, a form and a number of blocks of a system proceeding from technological (economical) reasons; (b) using the proposed synthesis method, to find an orientation of site magnetization providing maximum possible effect of magnet utilization in a system obtained in (a). Such approach considerably reduces a time of MSs projecting and guarantees maximal possible efficiency of magnets utilization. Besides it provides absolute assurance in 'ideality' of a MS design and allows to obtain an exact estimate of the limit parameters of a field in a working area of a projected MS. The method is applicable to a system containing the components from soft magnetic material with linear magnetic properties
Regular black holes in de Sitter universe: scalar field perturbations and quasinormal modes
Fernando, Sharmanthie
2015-01-01
The purpose of this paper is to study quasinormal modes (QNM) of a regular black hole with a cosmological constant due to scalar perturbations. A detailed study of the QNM frequencies for the massless scalar field were done by varying the parameters of the theory such as the mass, magnetic charge, cosmological constant, and the spherical harmonic index. We have employed the sixth order WKB approximation to compute the QNM frequencies. We have also proved analytically that the $l=0$ mode for the massless field reach a constant value at late times. We have approximated the near-extreme regular-de Sitter black hole potential with the P$\\ddot{o}$schl-Teller potential to obtain exact frequencies. The null geodesics of the regular-de Sitter black hole is employed to describe the QNM frequencies at the eikonal limit ($ l >>1$).
Quasistationary solutions of scalar fields around accreting black holes
Sanchis-Gual, Nicolas; Izquierdo, Paula; Font, José A; Montero, Pedro J
2016-01-01
Massive scalar fields can form long-lived configurations around black holes. These configurations, dubbed quasi-bound states, have been studied both in the linear and nonlinear regimes. In this paper we show that quasi-bound states can form in a dynamical scenario in which the mass of the black hole grows significantly due to the capture of infalling matter. We solve the Klein-Gordon equation numerically in spherical symmetry, mimicking the evolution of the spacetime through a sequence of analytic Schwarzschild black hole solutions of increasing mass. It is found that the frequency of oscillation of the quasi-bound states decreases as the mass of the black hole increases. In addition, accretion leads to a significative increase of the exponential decay of the scalar field energy due to the presence of terms of order higher than linear in the exponent. We compare the black hole mass growth rates used in our study with estimates from observational surveys and extrapolate our results to values of the scalar fiel...
On the Effects of Coupled Scalar Fields on Structure Formation
Li, Baojiu
2010-01-01
A coupling between a scalar field (representing the dark energy) and dark matter could produce rich phenomena in cosmology. It affects cosmic structure formation mainly through the fifth force, a velocity-dependent force that acts parallel to particle's direction of motion and proportional to its speed, an effective rescaling of the particle masses, and a modified background expansion rate. In many cases these effects entangle and it is difficult to see which is the dominant one. Here we perform N-body simulations to study their qualitative behaviour and relative importance in affecting the key structure formation observables, for a model with exponential scalar field coupling. We find that the fifth force, a prominent example of the scalar-coupling effects, is far less important than the rescaling of particle mass or the modified expansion rate. In particular, the rescaling of particle masses is shown to be the key factor leading to less concentration of particles in halos than in LCDM, a pattern which is al...
Extension of warm inflation to non-canonical scalar fields
Zhang, Xiao-Min
2014-01-01
We extend the warm inflationary scenario to the case of the non-canonical scalar fields. The equation of motion and the other basic equations of this new scenario are obtained. The Hubble damped term is enhanced in non-canonical inflation. A linear stability analysis is performed to give the proper slow roll conditions in warm non-canonical inflation. We study the density fluctuations in the new picture and obtain an approximate analytic expression of the power spectrum. The energy scale at the horizon crossing is depressed by both non-canonical effect and thermal effect, so does the tensor-to-scalar ratio. Besides the synergy, the non-canonical effect and the thermal effect are competing in the case of the warm non-canonical inflation.
Orbital angular momentum of scalar field generated by gravitational scatterings
Nishikawa, Ryusuke; Masuda, Atsuki; Nambu, Yasusada; Ishihara, Hideki
2016-01-01
It has been expected that astronomical observations to detect the orbital angular momenta of electromagnetic waves may give us a new insight into astrophysics. Previous works pointed out the possibility that a rotating black hole can produce orbital angular momenta of electromagnetic waves through gravitational scattering, and the spin parameter of the black hole can be measured by observing them. However, the mechanism how the orbital angular momentum of the electromagnetic wave is generated by the gravitational scattering has not been clarified sufficiently. In this paper, in order to understand it from a point of view of gravitational lensing effects, we consider an emitter which radiates a spherical wave of the real massless scalar field and study the deformation of the scalar wave by the gravitational scattering due to a black hole by invoking the geometrical optics approximation. We show that the frame dragging caused by the rotating black hole is not a necessary condition for generating the orbital ang...
Mass hierarchies and nondecoupling in multi-scalar-field dynamics
International Nuclear Information System (INIS)
In this work, we study the effects of field space curvature on scalar field perturbations around an arbitrary background field trajectory evolving in time. Nontrivial imprints of the 'heavy' directions on the low-energy dynamics arise when the vacuum manifold of the potential does not coincide with the span of geodesics defined by the sigma model metric of the full theory. When the kinetic energy is small compared to the potential energy, the field traverses a curve close to the vacuum manifold of the potential. The curvature of the path followed by the fields can still have a profound influence on the perturbations, as modes parallel to the trajectory mix with those normal to it if the trajectory turns sharply enough. We analyze the dynamical mixing between these nondecoupled degrees of freedom and deduce its nontrivial contribution to the low-energy effective theory for the light modes. We also discuss the consequences of this mixing for various scenarios where multiple scalar fields play a vital role, such as inflation and low-energy compactifications of string theory.
Partition function of massless scalar field in Schwarzschild background
Sanyal, Abhik Kumar
2014-01-01
Using thermal value of zeta function instead of zero temperature, the partition function of quantized fields in arbitrary stationary backgrounds was found to be independent of undetermined regularization constant in even-dimension and the long drawn problem associated with the trace anomaly effect had been removed. Here, we explicitly calculate the expression for the coincidence limit so that the technique may be applied in some specific problems. A particular problem dealt with here is to calculate the partition function of massless scalar field in Schwarzschild background.
Entanglement of self interacting scalar fields in an expanding spacetime
Alexander, Helder; Mansfield, Paul; da Paz, I G; Sampaio, Marcos
2016-01-01
We evaluate self-interaction effects on the quantum correlations of field modes of opposite momenta for scalar $\\lambda \\phi^4$ theory in a two-dimensional asymptotically flat Robertson-Walker spacetime. Such correlations are encoded both in the von-Neumann entropy defined through the reduced density matrix in one of the modes and in the covariance expressed in terms of the expectation value of the number operators for each mode in the evolved state. The entanglement between field modes carries information about the underlying spacetime evolution.
Geometrical destabilization of heavy scalar fields during inflation
Renaux-Petel, Sébastien
2015-01-01
We show the existence of a general mechanism by which heavy scalar fields can be destabilized during inflation. It relies on the fact that the effective mass of fluctuations orthogonal to the inflationary direction contains a contribution proportional to the curvature tensor of the field space metric, and that it can render the entropic fluctuations tachyonic. We describe a simple and rather universal setup in which apparently benign higher-order operators trigger this instability. This phenomenon can prematurely end inflation and have important observational consequences, sometimes excluding models that would otherwise perfectly fit the data. More generally, it modifies the interpretation of cosmological constraints in terms of fundamental physics.
On particle creation by a time-dependent scalar field
International Nuclear Information System (INIS)
The probability of particles creation by a homogeneous scalar field Χ(t) is calculated. Explicit analytical expressions are obtained in two limiting cases in the quasiclassical approximation and in the framework of perturbation theory. In the case when the mass of the created particles is defined by the time-dependent field Χ(t) according to the expression gΧ(t) Ψ-barΨ, where Χ(t)=Χ0cos(ωt), it is shown that the creation probability is suppresed not exponentially, but as ω1/2. Some cosmological consequences of the results are discussed. 13 refs
Scalar field quasinormal frequencies of Reissner-Nordstr\\"om black hole surrounded by quintessence
Wu, Chen
2016-01-01
We evaluate the quasinormal modes of massless scalar field around Reissner-Nordstr$\\ddot{\\text{o}}$m black hole surrounded by a static and spherically symmetric quintessence by using the continued fraction method. The appropriate Frobenius series for three special cases of the quintessence parameter $ \\epsilon = -1/3, -2/3$ and $-1$ are derived successfully. We show that the variation of quasinormal frequencies with charge of the black hole and the quintessential parameters. The numerical results show that quintessence field decreases oscillation frequencies of all angular momentum $l$ modes and increases the damping time of $l>0$ modes.
Effects of Interaction Between Gravitation and Nonlinear Electrodynamics On Scalar Field Evolution
Institute of Scientific and Technical Information of China (English)
CHEN Ju-Hua; WANG Yong-Jiu
2011-01-01
In this paper we investigate the scalar field evolution in the dyadosphere spacetime by using the third-order WKB approximation.We find that the coupling term between the gravitation and the nonlinear electrodynamics makes the scalar field decay more quickly and it also makes the scalar field oscillate more slowly.On the other words, this coupling term takes effect on the scalar field evolution as a damping factor.At the same time these effects become more obvious for the scalar field with higher angle quantum number.
Scalar-field amplitudes in black-hole evaporation
International Nuclear Information System (INIS)
We consider the quantum-mechanical decay of a Schwarzschild-like black hole into almost-flat space and weak radiation at a very late time. That is, we are concerned with evaluating quantum amplitudes (not just probabilities) for transitions from initial to final states. In this quantum description, no information is lost because of the black hole. The Lagrangian is taken, in the first instance, to consist of the simplest locally supersymmetric generalization of Einstein gravity and a massless scalar field. The quantum amplitude to go from given initial to final bosonic data in a slightly complexified time-interval T=τexp(-iθ) at infinity may be approximated by the form constxexp(-I), where I is the (complex) Euclidean action of the classical solution filling in between the boundary data. Additionally, in a pure supergravity theory, the amplitude constxexp(-I) is exact. Suppose that Dirichlet boundary data for gravity and the scalar field are posed on an initial spacelike hypersurface extending to spatial infinity, just prior to collapse, and on a corresponding final spacelike surface, sufficiently far to the future of the initial surface to catch all the Hawking radiation. Only in an averaged sense will this radiation have an approximately spherically-symmetric distribution. If the time-interval T had been taken to be exactly real, then the resulting 'hyperbolic Dirichlet boundary-value problem' would, as is well known, not be well posed. Provided instead ('Euclidean strategy') that one takes T complex, as above (0<θ=<π/2), one expects that the field equations become strongly elliptic, and that there exists a unique solution to the classical boundary-value problem. Within this context, by expanding the bosonic part of the action to quadratic order in perturbations about the classical solution, one obtains the quantum amplitude for weak-field final configurations, up to normalization. Such amplitudes are here calculated for weak final scalar fields
Self-Force on a Scalar Charge in Circular Orbit around a Schwarzschild Black Hole
Nakano, Hiroyuki; Mino, Yasushi; Sasaki, Misao
2001-01-01
In an accompanying paper, we have formulated two types of regulariz_ation methods to calculate the scalar self-force on a particle of charge $q$ moving around a black hole of mass $M$, one of which is called the ``power expansion regularization''. In this paper, we analytically evaluate the self-force (which we also call the reaction force) to the third post-Newtonian (3PN) order on the scalar particle in circular orbit around a Schwarzschild black hole by using the power expansion regulariza...
Sensitivity of atom interferometry to ultralight scalar field dark matter
Geraci, Andrew A
2016-01-01
We discuss the use of atom interferometry as a tool to search for Dark Matter (DM) composed of ultra-light scalar fields. Previous work on ultra-light DM detection using accelerometers has considered the possibility of equivalence principle violating effects whereby gradients in the dark matter field can directly produce relative accelerations between media of differing composition. In atom interferometers, we find that time-varying phase signals from oscillatory, or dilaton-like, DM can also arise due to changes in the atom rest mass that can occur between light-pulses throughout the interferometer sequence as well as changes in the earth's gravitational field. We estimate that several orders of magnitude of unexplored phase space for light DM fields can be probed with our proposed method.
Scalar field collapse in a conformally flat spacetime
Chakrabarti, Soumya
2016-01-01
The collapse scenario of a scalar field along with a perfect fluid distribution is investigated for a conformally flat spacetime. The theorem for the integrability of an anharmonic oscillator has been utilized. For a pure power law potential of the form ${\\phi}^{n+1}$, it is found that a central singularity is formed which is covered by an apparent horizon for $n>0$ and $n<-3$. Some numerical results have also been presented for a combination of two different powers of $\\phi$ in the potential.
Observable Effects of Scalar Fields and Varying Constants
Barrow, J D; Barrow, John D.; Shaw, Douglas J.
2006-01-01
We show by using the method of matched asymptotic expansions that a sufficient condition can be derived which determines when a local experiment will detect the cosmological variation of a scalar field which is driving the spacetime variation of a supposed constant of Nature. We extend our earlier analyses of this problem by including the possibility that the local region is undergoing collapse inside a virialised structure, like a galaxy or galaxy cluster. We show by direct calculation that the sufficient condition is met to high precision in our own local region and we can therefore legitimately use local observations to place constraints upon the variation of "constants" of Nature on cosmological scales.
Slowly rotating scalar field wormholes: The second order approximation
International Nuclear Information System (INIS)
We discuss rotating wormholes in general relativity with a scalar field with negative kinetic energy. To solve the problem, we use the assumption about slow rotation. The role of a small dimensionless parameter plays the ratio of the linear velocity of rotation of the wormhole's throat and the velocity of light. We construct the rotating wormhole solution in the second-order approximation with respect to the small parameter. The analysis shows that the asymptotical mass of the rotating wormhole is greater than that of the nonrotating one, and the null energy condition violation in the rotating wormhole spacetime is weaker than that in the nonrotating one.
Complex solutions for the scalar field model of the Universe
Lyons, Glenn W.
1992-08-01
The Hartle-Hawking proposal is implemented for Hawking's scalar field model of the Universe. For this model the complex saddle-point geometries required by the semiclassical approximation to the path integral cannot simply be deformed into real Euclidean and real Lorentzian sections. Approximate saddle points are constructed which are fully complex and have contours of real Lorentzian evolution. The semiclassical wave function is found to give rise to classical spacetimes at late times and extra terms in the Hamilton-Jacobi equation do not contribute significantly to the potential.
Stable cosmological models driven by a free quantum scalar field
Energy Technology Data Exchange (ETDEWEB)
Dappiaggi, C.; Pinamonti, N. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik]|[Citta Univ., Roma (Italy). Istituto Nazionale di Alta Matematica ' ' F. Severi' ' - GNFM; Fredenhagen, K. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik
2008-01-15
In the mathematically rigorous analysis of semiclassical Einstein's equations, the renormalisation of the stress-energy tensor plays a crucial role. We address such a topic in the case of a scalar field with both arbitrary mass and coupling with gravity in the hypothesis that the underlying algebraic quantum state is of Hadamard type. Particularly, if we focus on highly symmetric solutions of the semiclassical Einstein's equations, the envisaged method displays a de Sitter type behaviour even without an a priori introduced cosmological constant. As a further novel result we shall show that these solutions turn out to be stable. (orig.)
Supersymmetric Homogeneous Quantum Cosmologies Coupled to a Scalar Field
Bene, J
1994-01-01
Recent work on $N=2$ supersymmetric Bianchi type IX cosmologies coupled to a scalar field is extended to a general treatment of homogeneous quantum cosmologies with explicitely solvable momentum constraints, i.e. Bianchi types I, II, VII, VIII besides the Bianchi type IX, and special cases, namely the Friedmann universes, the Kantowski-Sachs space, and Taub-NUT space. Besides the earlier explicit solution of the Wheeler DeWitt equation for Bianchi type IX, describing a virtual wormhole fluctuation, an additional explicit solution is given and identified with the `no-boundary state'.
Higgs particles interacting via a scalar Dark Matter field
Bhattacharya, Yajnavalkya
2016-01-01
We study a system of two Higgs bound state, interacting via a real scalar Dark Matter mediating field, without imposing $Z_2$ symmetry on the DM sector of the postulated Lagrangian. The variational method in the Hamiltonian formalism of QFT is used to derive relativistic wave equations for the two-Higgs system, using a truncated Fock-space trial state. Approximate solutions of the 2-body relativistic coupled integral equations are presented, and conditions for the existence of Higgs bound states is examined in a broad parameter space of DM mass and coupling constants.
Hydrodynamic transport coefficients in relativistic scalar field theory
Jeon, S
1995-01-01
Hydrodynamic transport coefficients may be evaluated from first principles in a weakly coupled scalar field theory at arbitrary temperature. In a theory with cubic and quartic interactions, the infinite class of diagrams which contribute to the leading weak coupling behavior are identified and summed. The resulting expression may be reduced to a single linear integral equation, which is shown to be identical to the corresponding result obtained from a linearized Boltzmann equation describing effective thermal excitations with temperature dependent masses and scattering amplitudes. The effective Boltzmann equation is valid even at very high temperature where the thermal lifetime and mean free path are short compared to the Compton wavelength of the fundamental particles.
Free evolution of nonlinear scalar field collapse in double-null coordinates
Burko, L M
1999-01-01
We study numerically the fully nonlinear spherically-symmetric collapse of a self-gravitating, minimally-coupled, massless scalar field. Our numerical code is based on double-null coordinates and on free evolution of the metric functions and the scalar field. The numerical code is stable and second-order accurate. We use this code to study the late-time asymptotic behavior at fixed $r$ (outside the black hole), along the event horizon, and along future null infinity. In all three asymptotic regions we find that, after the decay of the quasi-normal modes, the perturbations are dominated by inverse power-law tails. The corresponding power indices agree with the integer values predicted by linearized theory. We also study the case of a charged black hole nonlinearly perturbed by a (neutral) self-gravitating scalar field, and find the same type of behavior---i.e., quasi-normal modes followed by inverse power-law tails, with the same indices as in the uncharged case.
Stable, Renormalizable, Scalar Tachyonic Quantum Field Theory with Chronology Protection
Radzikowski, Marek J
2008-01-01
We use microlocal arguments to suggest that Lorentz symmetry breaking must occur in a reasonably behaved tachyonic quantum field theory that permits renormalizability. In view of this, we present a scalar tachyonic quantum field model with manifestly broken Lorentz symmetry and without exponentially growing/decaying modes. A notion of causality, in which anti-telephones are excluded, and which is viewed as a form of chronology protection, is obeyed. The field theory is constructed in a preferred tachyon frame in terms of commuting creation/annihilation operators. We calculate some sample (renormalized) operators in this preferred frame, argue that the Hadamard condition is satisfied, and discuss the PCT and spin-statistics theorems for this model.
Correspondence between Generalized Dark Energy and Scalar Field Dark Energies
Maity, Sayani; Debnath, Ujjal
2015-07-01
In this work, we have considered non-flat FRW universe filled with dark matter (with non-zero pressure) and generalized dark energy (GDE) as motivated by the work of Sharif et al. (Mod. Phys. Lett. A 28, 1350180, 2013). Also the dark matter and the dark energy are considered to be interacting. The energy density, pressure and the EoS of the GDE have been calculated for the interacting scenario. For stability analysis of this model, we have also analyzed the sign of square speed of sound. Next we investigate the correspondence between GDE and different other candidates of dark energies such as DBI-essence, tachyonic field, hessenc and electromagnetic field. Also we have reconstructed the potential functions and the scalar fields in this scenario.
Casimir effect for a scalar field via Krein quantization
International Nuclear Information System (INIS)
In this work, we present a rather simple method to study the Casimir effect on a spherical shell for a massless scalar field with Dirichlet boundary condition by applying the indefinite metric field (Krein) quantization technique. In this technique, the field operators are constructed from both negative and positive norm states. Having understood that negative norm states are un-physical, they are only used as a mathematical tool for renormalizing the theory and then one can get rid of them by imposing some proper physical conditions. -- Highlights: • A modification of QFT is considered to address the vacuum energy divergence problem. • Casimir energy of a spherical shell is calculated, through this approach. • In this technique, it is shown, the theory is automatically regularized
Geib, Tanja; Merle, Alexander; No, Jose Miguel; Panizzi, Luca
2015-01-01
We discuss how the intensity and the energy frontiers provide complementary constraints within a minimal model of neutrino mass involving just one new field beyond the Standard Model at accessible energy, namely a doubly charged scalar $S^{++}$ and its antiparticle $S^{--}$. In particular we focus on the complementarity between high-energy LHC searches and low-energy probes such as lepton flavor violation. Our setting is a prime example of how high- and low-energy physics can cross-fertilize each other.
Geib, Tanja; King, Stephen F.; Merle, Alexander; No, Jose Miguel; Panizzi, Luca
2016-04-01
We discuss how the intensity and the energy frontiers provide complementary constraints within a minimal model of neutrino mass involving just one new field beyond the Standard Model at accessible energy, namely a doubly charged scalar S++ and its antiparticle S-- . In particular, we focus on the complementarity between high-energy LHC searches and low-energy probes such as lepton flavor violation. Our setting is a prime example of how high- and low-energy physics can cross-fertilize each other.
Decay of massive scalar field in a black hole background immersed in magnetic field
Energy Technology Data Exchange (ETDEWEB)
Wu, Chen [Chinese Academy of Sciences, Shanghai Institute of Applied Physics, Shanghai (China); Xu, Renli [Nanjing University, Key Laboratory of Modern Acoustics, Department of Physics, Nanjing (China)
2015-08-15
We evaluate quasinormal modes of a massive scalar field of the Ernst spacetime, an exact solution of the Einstein-Maxwell equations, describing a black hole immersed in a uniform magnetic field B. It is well known that the quasinormal spectrum for a massive scalar field in the vicinity of the magnetized black holes acquires an effective mass μ{sub eff} = √(4B{sup 2}m{sup 2}+μ{sup 2}), where m is the azimuthal number and μ is the mass of scalar field. The numerical result shows that increasing of the field effective mass and the magnetic field B gives rise to decreasing of the imaginary part of the quasinormal modes until reaching a vanishing damping rate. (orig.)
Bianchi type-I cosmology with scalar and spinor fields
International Nuclear Information System (INIS)
We consider a self-consistent system of interacting spinor and scalar fields within the framework of a Bianchi type-I (BI) cosmological model filled with perfect fluid. The interacting term in the Lagrangian is chosen in the form of derivative coupling, i.e., Lint=(λ/2)φ,αφ,αF. Here F is a power or trigonometric function of the invariants I and/or J constructed from bilinear spinor forms S=ψ-bar ψ and P=iψ-barγ5ψ. Self-consistent solutions to the spinor, scalar, and BI gravitational field equations are obtained. The problems of an initial singularity and the asymptotically isotropization process of the initially anisotropic space-time are studied. The role of the cosmological constant (Λ term) in the evolution of a BI Universe is studied. It is shown that a positive Λ generates an oscillatory mode of expansion of the BI model, whereas if F in Lint is chosen to be a trigonometric function of its arguments, there exists a nonexponential mode of evolution even with a negative Λ. It is shown also that for a suitable choice of problem parameters the present model allows regular solutions without a broken dominant energy condition
Bouncing scalar field cosmology in the polymeric minisuperspace picture
Vakili, B; Hosseinzadeh, V; Gorji, M A
2014-01-01
We study a cosmological setup consisting of a FRW metric as the background geometry with a massless scalar field in the framework of classical polymerization of a given dynamical system. To do this, we first introduce the polymeric representation of the quantum operators. We then extend the corresponding process to reach a transformation which maps any classical variable to its polymeric counterpart. It is shown that such a formalism has also an analogue in terms of the symplectic structure, i.e., instead of applying polymerization to the classical Hamiltonian to arrive its polymeric form, one can use a new set of variables in terms of which Hamiltonian retains its form but now the corresponding symplectic structure gets a new deformed functional form. We show that these two methods are equivalent and by applying of them to the scalar field FRW cosmology see that the resulting scale factor exhibits a bouncing behavior from a contraction phase to an expanding era. Since the replacing of the big bang singularit...
A brief Review of the Scalar Field Dark Matter model
Magaña, Juan; Robles, Victor; Suárez, Abril
2012-01-01
In the last time the cold dark matter (CDM) model has suggested more and more that it is not able to describe all the properties of nearby galaxies that can be observed in great detail as well as that it has some problems in the mechanism by which matter is more rapidly gathered into large-scale structure such as galaxies and clusters of galaxies. In this work we revisit an alternative model, the scalar field dark matter (SFDM) model, which proposes that the galactic haloes form by condensation of a scalar field (SF) very early in the Universe, i.e., in this model the haloes of galaxies are astronomical Bose-Einstein Condensate drops of SF. On the other hand, large-scale structures like clusters or superclusters of galaxies form similar to the $\\Lambda$CDM model, by hierarchy, thus all the predictions of the $\\Lambda$CDM model at cosmological scales are reproduced by SFDM. This model predicts that all galaxy haloes must be very similar and exist for higher redshifts than in the $\\Lambda$CDM model. In the firs...
Directory of Open Access Journals (Sweden)
Ran Li
2016-07-01
Full Text Available Reissner–Nordström Anti-de Sitter (RNAdS black holes are unstable against the charged scalar field perturbations due to the well-known superradiance phenomenon. We present the time domain analysis of charged scalar field perturbations in the RNAdS black hole background in general dimensions. We show that the instabilities of charged scalar field can be explicitly illustrated from the time profiles of evolving scalar field. By using the Prony method to fit the time evolution data, we confirm the mode that dominates the long time behavior of scalar field is in accordance with the quasinormal mode from the frequency domain analysis. The superradiance origin of the instability can also be demonstrated by comparing the real part of the dominant mode with the superradiant condition of charged scalar field. It is shown that all the unstable modes are superradiant, which is consistent with the analytical result in the frequency domain analysis. Furthermore, we also confirm there exists the rapid exponential growing modes in the RNAdS case, which makes the RNAdS black hole a good test ground to investigate the nonlinear evolution of superradiant instability.
Inflation in a conformally invariant two-scalar-field theory with an extra R2 term
International Nuclear Information System (INIS)
We explore inflationary cosmology in a theory where there are two scalar fields which non-minimally couple to the Ricci scalar and an additional R2 term, which breaks the conformal invariance. Particularly, we investigate the slow-roll inflation in the case of one dynamical scalar field and that of two dynamical scalar fields. It is explicitly demonstrated that the spectral index of the scalar mode of the density perturbations and the tensor-to-scalar ratio can be consistent with the observations obtaind by the recent Planck satellite. The graceful exit from the inflationary stage is achieved as in convenient R2 gravity. We also propose the generalization of the model under discussion with three scalar fields
Conformally coupled scalar black holes admit a flat horizon due to axionic charge
Bardoux, Yannis; Charmousis, Christos
2012-01-01
Static, charged black holes in the presence of a negative cosmological constant and with a planar horizon are found in four dimensions. The solutions have scalar secondary hair. We claim that these constitute the planar version of the Martinez-Troncoso-Zanelli black holes, only known up to now for a curved event horizon in four dimensions. Their planar version is rendered possible due to the presence of two, equal and homogeneously distributed, axionic charges dressing the flat horizon. The solutions are presented in the conformal and minimal frame and their basic properties and thermodynamics analysed. Entertaining recent applications to holographic superconductors, we expose two branches of solutions: the undressed axionic Reissner-Nordstrom-AdS black hole, and the novel black hole carrying secondary hair. We show that there is a critical temperature at which the (bald) axionic Reissner-Nordstrom-AdS black hole undergoes a second order phase transition to the hairy black hole spontaneously acquiring scalar ...
Boson Stars in a Theory of Complex Scalar Fields coupled to $U(1)$ Gauge Field and Gravity
Kumar, Sanjeev; Kulshreshtha, Daya Shankar
2016-01-01
We study boson shells and boson stars in a theory of complex scalar field coupled to the $U(1)$ gauge field $A_{\\mu}$ and Einstein gravity with the potential: $V(|\\Phi|) := \\frac{1}{2} m^{2} \\left(|\\Phi|+ a \\right)^2$. This could be considered either as a theory of massive complex scalar field coupled to electromagnetic field and gravity in a conical potential or as a theory in the presence of a potential which is an overlap of a parabolic and a conical potential. Our theory has a positive cosmological constant $(\\Lambda := 4 \\pi G m^2 a^2)$. Boson stars are found to come in two types, having either ball-like or shell-like charge density. We have studied the properties of these solutions and have also determined their domains of existence for some specific values of the parameters of the theory. Similar solutions have also been obtained by Kleihaus, Kunz, Laemmerzahl and List, in a V-shaped scalar potential.
Quantum theory of relativistic charged particles in external fields
International Nuclear Information System (INIS)
A study was made on external field theories in which the quantized field corresponds to relativistic elementary particles with non-zero rest mass. These particles are assumed to be charged, thus they have distinct antiparticles. The thesis consists of two parts. The first tries to accommodate the general features of theories of relativistic charged particles in external fields. Spin and dynamics in particular are not specified. In the second part, the results are applied to charged spin-1/2 and spin-0 particles, the dynamics of which are given by the Dirac resp. Klein-Gordon equation. The greater emphasis is on external fields which are rapidly decreasing, infinitely differentiable functions of space-time, but also considers time-independent fields. External fields, other than electromagnetic fields are also considered, e.g. scalar fields
Strong deflection lensing by charged black holes in scalar-tensor gravity
Energy Technology Data Exchange (ETDEWEB)
Eiroa, Ernesto F.; Sendra, Carlos M. [Instituto de Astronomia y Fisica del Espacio (IAFE, CONICET-UBA), Buenos Aires (Argentina); Universidad de Buenos Aires, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina)
2014-11-15
We examine a class of charged black holes in scalar-tensor gravity as gravitational lenses. We find the deflection angle in the strong deflection limit, from which we obtain the positions and the magnifications of the relativistic images. We compare our results with those corresponding to the Reissner-Norstroem spacetime and we analyze the observational aspects in the case of the Galactic supermassive black hole. (orig.)
Quantization of massive scalar fields over static black string backgrounds
Piedra, Owen Pavel Fernandez
2007-01-01
The renormalized mean value of the corresponding components of the Energy-Momentum tensor for massive scalar fields coupled to an arbitrary gravitational field configuration having cylindrical symmetry are analytically evaluated using the Schwinger-DeWitt approximation, up to second order in the inverse mass value. The general results are employed to explicitly derive compact analytical expressions for the Energy-Momentum tensor in the particular background of the Black-String spacetime. In the case of the Black String considered in this work, we proof that a violation of the weak energy condition occur at the horizon of the space-time for values of the coupling constant, that include as particular cases the most interesting of minimal and conformal coupling.
Locally smeared operator product expansions in scalar field theory
Monahan, Christopher
2015-01-01
We propose a new "locally smeared operator product expansion" (sOPE) to decompose non-local operators in terms of a basis of smeared operators. The sOPE formally connects nonperturbative matrix elements determined numerically using lattice field theory to matrix elements of non-local operators in the continuum. These nonperturbative matrix elements do not suffer from power-divergent mixing on the lattice, which significantly complicates calculations of quantities such as the moments of parton distribution functions, provided the smearing scale is kept fixed in the continuum limit. The presence of this smearing scale complicates the connection to the Wilson coefficients of the standard operator product expansion and requires the construction of a suitable formalism. We demonstrate the feasibility of our approach with examples in real scalar field theory.
Self Tuning Scalar Fields in Spherically Symmetric Spacetimes
Appleby, Stephen
2015-01-01
We search for self tuning solutions to the Einstein-scalar field equations for the simplest class of `Fab-Four' models with constant potentials. We first review the conditions under which self tuning occurs in a cosmological spacetime, and by introducing a small modification to the original theory - introducing the second and third Galileon terms - show how one can obtain de Sitter states where the expansion rate is independent of the vacuum energy. We then consider whether the same self tuning mechanism can persist in a spherically symmetric inhomogeneous spacetime. We show that there are no asymptotically flat solutions to the field equations in which the vacuum energy is screened, other than the trivial one (Minkowski space). We then consider the possibility of constructing Schwarzschild de Sitter spacetimes for the modified Fab Four plus Galileon theory. We argue that the only model that can successfully screen the vacuum energy in both an FLRW and Schwarzschild de Sitter spacetime is one containing `John...
Quark scalar, axial and tensor charges in the Schwinger-Dyson formalism
Energy Technology Data Exchange (ETDEWEB)
Yamanaka, Nodoka [2-1 Hirosawa, Wako, 351-0198 Saitama (Japan)
2016-01-22
The quark scalar, axial and tensor charges of nucleon are calculated in the Schwinger-Dyson formalism. We first calculate these charges in the rainbow-ladder truncation using the IR cut quark-gluon vertex, and show that the result is in agreement with the known data. We then perform the same calculation with the phenomenological IR singular quark-gluon vertex. In this case, the Schwinger-Dyson equation does not converge. We show that this result suggests the requirement of additional corrections to the rainbow-ladder truncation, due to the interaction between quark and gluons in the deep IR region.
Quark scalar, axial and tensor charges in the Schwinger-Dyson formalism
International Nuclear Information System (INIS)
The quark scalar, axial and tensor charges of nucleon are calculated in the Schwinger-Dyson formalism. We first calculate these charges in the rainbow-ladder truncation using the IR cut quark-gluon vertex, and show that the result is in agreement with the known data. We then perform the same calculation with the phenomenological IR singular quark-gluon vertex. In this case, the Schwinger-Dyson equation does not converge. We show that this result suggests the requirement of additional corrections to the rainbow-ladder truncation, due to the interaction between quark and gluons in the deep IR region
A search for charged scalar particles pair produced in e+e- annihilation
International Nuclear Information System (INIS)
We have searched for unstable charged scalar particles (S+-) such as techni-pions or charged Higgs particles pair produced in high energy e+e- annihilation. No evidence for such particles was observed in both decay modes e+e- → S+S- → (tauν)(hadrons) and → (tauν)(tauν). Upper limits of 4 to 11% are obtained for the branching ratio S+- → (tauν) in the S+- mass range between 4 to 12 GeV. (orig.)
Cosmological Model with Nonminimal Derivative Coupling of Scalar Fields in Five Dimensions
Suroso, Agus
2014-01-01
We study a nonminimal derivative coupling (NMDC) of scalar field, where the scalar field is coupled to curvature tensor in the five dimensional universal extra dimension model. We apply the Einstein equation and find its solution. First, we consider a special case of pure free scalar field without NMDC and we find that for static extradimension, the solution is equivalent to the standard cosmology with stiff matter. For a general case of pure free scalar field with NMDC, we find that the de Sitter solution is the solution of our model. For this solution, the scalar field evolves linearly in time. In the limit of small Hubble parameter, the general case give us the same solution as in the pure free scalar field. Finally, we perform a dynamical analysis to determine the stability of our model. We find that the extradimension, if it exist, can not be static and always shrinks with the expansion of four dimensional spacetime.
Nandi, Debottam
2016-01-01
In this work, we present a consistent Hamiltonian analysis of cosmological perturbations for generalized non-canonical scalar fields. In order to do so, we introduce a new phase-space variable that is uniquely defined for different non-canonical scalar fields. We also show that this is the simplest and efficient way of expressing the Hamiltonian. We extend the Hamiltonian approach of [arXiv:1512.02539] to non-canonical scalar field and obtain a new definition of speed of sound in phase-space. In order to invert generalized phase-space Hamilton's equations to Euler-Lagrange equations of motion, we prescribe a general inversion formulae and show that our approach for non-canonical scalar field is consistent. We also obtain the third and fourth order interaction Hamiltonian for generalized non-canonical scalar fields and briefly discuss the extension of our method to generalized Galilean scalar fields.
Backreaction to wormhole by classical scalar field: Will classical scalar field destroy wormhole?
Kim, Sung-Won
1999-01-01
There are two effects of extra matter fields on the Lorentzian traversable wormhole. The ``primary effect'' says that the extra matter can afford to be a part of source or whole source of the wormhole when the wormhole is being formed. Thus the matter does not affect the stability of wormhole and the wormhole is still safe. If the extra matter is extotic, it can be the whole part of the source of the wormhole. The ``auxiliary effect'' is that the extra matter plays the role of the additional ...
Comments on Unified dark energy and dark matter from a scalar field different from quintessence
Chimento, Luis P.; Forte, Mónica
2010-01-01
In a recent paper by C. Gao, M. Kunz, A. Liddle and D. Parkinson [arXiv:0912.0949], the unification of dark matter and dark energy was explored within a theory containing a scalar field of non-Lagrangian type. This scalar field, different from the classic quintessence, can be obtained from the scalar field representation of an interacting two-fluid mixture described in the paper by L.P. Chimento and M. Forte [arXiv:0706.4142
Neutron Star Structure in the Presence of Conformally Coupled Scalar Fields
Sultana, Joseph; Bose, Benjamin; Kazanas, Demosthenes
2014-01-01
Neutron star models are studied in the context of scalar-tensor theories of gravity in the presence of a conformally coupled scalar field, using two different numerical equations of state (EoS) representing different degrees of stiffness. In both cases we obtain a complete solution by matching the interior numerical solution of the coupled Einstein-scalar field hydrostatic equations, with an exact metric on the surface of the star. These are then used to find the effect of the scalar field and its coupling to geometry, on the neutron star structure, particularly the maximum neutron star mass and radius. We show that in the presence of a conformally coupled scalar field, neutron stars are less dense and have smaller masses and radii than their counterparts in the minimally coupled case, and the effect increases with the magnitude of the scalar field at the center of the star.
The Model for Final Stage of Gravitational Collapse Massless Scalar Field
Gladush, V. D.; Mironin, D. V.
It is known that in General relativity, for some spherically symmetric initial conditions, the massless scalar field (SF) experience the gravitational collapse (Choptuik, 1989), and arise a black hole (BH). According Bekenstein, a BH has no "hair scalar", so the SF is completely under the horizon. Thus, the study of the final stage for the gravitational collapse of a SF is reduced to the construction of a solution of Einstein's equations describing the evolution of a SF inside the BH. In this work, we build the Lagrangian for scalar and gravitationalfields in the spherically symmetric case, when the metric coefficients and SF depends only on the time. In this case, it is convenient to use the methods of classical mechanics. Since the metric allows an arbitrary transformation of time, then the corresponding field variable (g00) is included in the Lagrangian without time derivative. It is a non-dynamic variable, and is included in the Lagrangian as a Lagrange multiplier. A variation of the action on this variable gives the constraint. It turns out that Hamiltonian is proportional to the constraint, and so it is zero. The corresponding Hamilton-Jacobi equation easily integrated. Hence, we find the relation between the SF and the metric. To restore of time dependence we using an equation dL / dq' = dS / dq After using a gauge condition, it allows us to find solution. Thus, we find the evolution of the SF inside the BH, which describes the final stage of the gravitational collapse of a SF. It turns out that the mass BH associated with a scalar charge G of the corresponding SF inside the BH ratio M = G/(2√ κ).
The Real Scalar Field in Schwarzschild-de Sitter Spacetime
Tian, J; Guo, G; Lv, Y; Zhang, S; Wang, W; Tian, Jianxiang; Gui, Yuanxing; Guo, Guanghai; Lv, Yan; Zhang, Suhong; Wang, Wei
2003-01-01
In this paper, the real scalar field equation in Schwarzschild-de Sitter spacetime is solved numerically with high precision. A method called polynomial approximation is introduced to derive the relation between the tortoise coordinate x and the radius r. This method is diﬀerent from the tangent approximation [1] and leads to more accurate result. The Nariai black hole is then discussed in details. We find that the wave function is harmonic only near the horizons as I. Brevik and B. Simonsen [1] found. Howerver the wave function is not harmonic in the region of the potential peak, with amplitude increasing instead. Furthermore, we also find that, when cosmological constant decreases, the potential peak increases, and the maximum wave amplitude increases.
Nonequlibrium dynamics of scalar fields in a thermal bath
Energy Technology Data Exchange (ETDEWEB)
Anisimov, A.; Buchmueller, W.; Drewes, M.; Mendizabal, S.
2008-12-15
We study the approach to equilibrium for a scalar field which is coupled to a large thermal bath. Our analysis of the initial value problem is based on Kadanoff-Baym equations which are shown to be equivalent to a stochastic Langevin equation. The interaction with the thermal bath generates a temperature-dependent spectral density, either through decay and inverse decay processes or via Landau damping. In equilibrium, energy density and pressure are determined by the Bose-Einstein distribution function evaluated at a complex quasi-particle pole. The time evolution of the statistical propagator is compared with solutions of the Boltzmann equations for particles as well as quasi-particles. The dependence on initial conditions and the range of validity of the Boltzmann approximation are determined. (orig.)
Free box^k Scalar Conformal Field Theory
Brust, Christopher
2016-01-01
We consider the generalizations of the free U(N) and O(N) scalar conformal field theories to actions with higher powers of the Laplacian, box^k, in general dimension d. We study the spectra, Verma modules, anomalies and OPE of these theories. We argue that in certain d and k, the spectrum contains zero norm operators which are both primary and descendant, as well as extension operators which are neither primary nor descendant. In addition, we argue that in even dimensions d <= 2k, there are well-defined operator algebras which are related to the box^k theories and are novel in that they have a finite number of single-trace states.
Detailed ultraviolet asymptotics for AdS scalar field perturbations
Evnin, Oleg
2016-01-01
We present a range of methods suitable for accurate evaluation of the leading asymptotics for integrals of products of Jacobi polynomials in limits when the degrees of some or all polynomials inside the integral become large. The structures in question have recently emerged in the context of effective descriptions of small amplitude perturbations in anti-de Sitter (AdS) spacetime. The limit of high degree polynomials corresponds in this situation to effective interactions involving extreme short-wavelength modes, whose dynamics is crucial for the turbulent instabilities that determine the ultimate fate of small AdS perturbations. We explicitly apply the relevant asymptotic techniques to the case of a self-interacting probe scalar field in AdS and extract a detailed form of the leading large degree behavior, including closed form analytic expressions for the numerical coefficients appearing in the asymptotics.
Approximation of the potential in scalar field dark energy models
Battye, Richard A
2016-01-01
We study the nature of potentials in scalar field based models for dark energy - both with canonical and non-canonical kinetic terms. We calculate numerically, and using an analytic approximation around $a\\approx 1$, potentials for models with constant equation-of-state parameter, $w_{\\phi}$. We find that for a wide range of models with canonical and non-canonical kinetic terms there is a simple approximation for the potential that holds when the scale factor is in the range $0.6\\lesssim a\\lesssim 1.4$. We discuss how this form of the potential can also be used to represent models with non-constant $w_{\\phi}$ and, hence, how it could be used in reconstruction from cosmological data.
Line-Integral Representations of the Diffraction of Scalar Fields
Lu, Yi-Chuan
2011-01-01
Traditionally, the diffraction of a scalar wave satisfying Helmholtz equation through an aperture on an otherwise black screen can be solved approximately by Kirchhoff's integral over the aperture. Rubinowicz, on the other hand, was able to split the solution into two parts: one is the geometrical part that appears only in the geometrical illuminated region, and the other representing the reflected wave is a line-integral along the edge of the aperture. However, this decomposition is not entirely satisfactory in the sense that the two separated fields are discontinuous at the boundary of the illuminated region. Also, the functional form of the line-integral is not what one would expect an ordinary reflection wave should be due to some confusing factors in the integrand. Finally, the boundary conditions on the screen imposed by Kirchhoff's approximation are mathematically inconsistent, and therefore, rigorously, this decomposition formulation must be slightly modified by taking into account the correct B.C.s. ...
Hydrodynamic transport coefficients in relativistic scalar field theory
International Nuclear Information System (INIS)
Hydrodynamic transport coefficients may be evaluated from first principals in a weakly coupled scalar field theory at an arbitrary temperature. In a theory with cubic and quartic interactions, the infinite class of diagrams which contributes to the leading weak coupling behavior is identified and summed. The resulting expression may be reduced to a single linear integral equation, which is shown to be identical to the corresponding result obtained from a linearized Boltzmann equation describing effective thermal excitations with temperature-dependent masses and scattering amplitudes. The effective Boltzmann equation is valid even at very high temperature where the thermal lifetime and mean free path are short compared to the Compton wavelength of the fundamental particles. Numerical results for the shear and the bulk viscosities are presented
Polymer-Fourier quantization of the scalar field revisited
Garcia-Chung, Angel
2016-01-01
The Polymer Quantization of the Fourier modes of the real scalar field is studied within algebraic scheme. We replace the positive linear functional of the standard Poincar\\'e invariant quantization by a singular one. This singular positive linear functional is constructed as mimicking the singular limit of the complex structure of the Poincar\\'e invariant Fock quantization. The resulting symmetry group of such Polymer Quantization is the subgroup $\\mbox{SDiff}(\\mathbb{R}^4)$ which is a subgroup of $\\mbox{Diff}(\\mathbb{R}^4)$ formed by spatial volume preserving diffeomorphisms. In consequence, this yields an entirely different irreducible representation of the Canonical Commutation Relations, non-unitary equivalent to the standard Fock representation. We also compared the Poincar\\'e invariant Fock vacuum with the Polymer Fourier vacuum.
Nonequilibrium Dynamics of Scalar Fields in a Thermal Bath
Anisimov, A; Drewes, M; Mendizabal, S
2008-01-01
We study the approach to equilibrium for a scalar field which is coupled to a large thermal bath. Our analysis of the initial value problem is based on Kadanoff-Baym equations which are shown to be equivalent to a stochastic Langevin equation. The interaction with the thermal bath generates a temperature-dependent spectral density, either through decay and inverse decay processes or via Landau damping. In equilibrium, energy density and pressure are determined by the Bose-Einstein distribution function evaluated at a complex quasi-particle pole. The time evolution of the statistical propagator is compared with solutions of the Boltzmann equations for particles as well as quasi-particles. The dependence on initial conditions and the range of validity of the Boltzmann approximation are determined.
Loop representation for 2-D Wilson lattice fermions in a scalar background field
Gattringer, Christof
1998-01-01
We show that the fermion determinant for 2-D Wilson lattice fermions coupled to an external scalar field is equivalent to self avoiding loops interacting with the external field. In an application of the resulting formula we integrate the scalar field with a Gaussian action to generate the N-component Gross-Neveu model. The loop representation for this model is discussed.
Kinky torsion in a Poincare gauge model of gravity coupled to a massless scalar field
International Nuclear Information System (INIS)
For the quadratic Poincare gauge theory coupled to a massless scalar field (''Higgs field'') we study spherically symmetric solutions with duality properties of the Riemann-Cartan curvature. We find an exact solution with a localized scalar field and a torsion kink both residing in an open einsteinian microcosmos. Via a new dynamical mechanism, the asymptotically constant torsion compensates the bare ''cosmological'' constant. (orig.)
Propagators of charged particles in an external magnetic field, expanded over Landau levels
Kuznetsov, A V; Shitova, A M
2015-01-01
Various forms of expressions for the propagators of charged particles in a constant magnetic field that should be used for investigations of electroweak processes in external uniform magnetic field are discussed. Formulas for the propagators of the Standard Model charged $W$- and scalar $\\Phi$-bosons in an arbitrary $\\xi$-gauge, expanded over Landau levels, are derived for the first time.
Isovector Scalar Field Effects in Asymmetric Nuclear Matter
Institute of Scientific and Technical Information of China (English)
WANG Zhi-Xia; LIU Bo; ZHANG Xi-He; SHEN Cai-Wan; SHEN Ke; M. Di Toro; ZHAO En-Guang
2008-01-01
Density-dependent parametrization models of the nucleon-meson coupling constants, including the isovector scalar δ-field, are applied to asymmetric nuclear matter. The nuclear equation of state (EOS) and the neutron star properties are studied in a relativistic Lagrangian density, using the relativistic mean field (RMF) hadron theory. It is known that the 5-field in the constant coupling scheme leads to a larger repulsion in dense neutron-rich matter and to a definite splitting of proton and neutron effective masses, finally influences the stability of the neutron stars. We use density-dependent models of the nucleon-meson couplings to study the properties of neutron star matter and to reexamine the δ-field effects in asymmetric nuclear matter. Our calculation shows that the stability conditions of the neutron star matter can be improved in presence of the 5-meson in the density-dependent models of the coupling constants. The EOS of nuclear matter strongly depends on the density dependence of the interactions.
On the existence of conformally coupled scalar field hair for black holes in (anti-)de Sitter space
Winstanley, Elizabeth(Consortium for Fundamental Physics, School of Mathematics and Statistics, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH, United Kingdom)
2002-01-01
The Einstein-conformally coupled scalar field system is studied in the presence of a cosmological constant. We consider a massless or massive scalar field with no additional self-interaction, and spherically symmetric black hole geometries. When the cosmological constant is positive, no scalar hair can exist and the only solution is the Schwarzschild-de Sitter black hole. When the cosmological constant is negative, stable scalar field hair exists provided the mass of the scalar field is not t...
Axial, Scalar and Tensor Charges of the Nucleon from 2+1+1-flavor Lattice QCD
Bhattacharya, Tanmoy; Cohen, Saul; Gupta, Rajan; Lin, Huey-Wen; Yoon, Boram
2016-01-01
We present results for the isovector axial, scalar and tensor charges $g^{u-d}_A$, $g^{u-d}_S$ and $g^{u-d}_T$ of the nucleon needed to probe the Standard Model and novel physics. The axial charge is a fundamental parameter describing the weak interactions of nucleons. The scalar and tensor charges probe novel interactions at the TeV scale in neutron and nuclear $\\beta$-decays, and the flavor-diagonal tensor charges $g^{u}_T$, $g^{d}_T$ and $g^{s}_T$ are needed to quantify the contribution of the quark electric dipole moment (EDM) to the neutron EDM. The lattice-QCD calculations were done using nine ensembles of gauge configurations generated by the MILC Collaboration using the HISQ action with 2+1+1 dynamical flavors. These ensembles span three lattice spacings $a \\approx 0.06, 0.09$ and $0.12$ fm and light-quark masses corresponding to the pion masses $M_\\pi \\approx$ 135, 225 and 315 MeV. High-statistics estimates on five ensembles using the all-mode-averaging method allow us to quantify all systematic unce...
Superfield approach to symmetry invariance in quantum electrodynamics with complex scalar fields
Indian Academy of Sciences (India)
R P Malik; B P Mandal
2009-05-01
We show that the Grassmannian independence of the super-Lagrangian density, expressed in terms of the superfields defined on a (4,2)-dimensional supermanifold, is a clear-cut proof for the Becchi–Rouet–Stora–Tyutin (BRST) and anti-BRST invariance of the corresponding four (3+1)-dimensional (4D) Lagrangian density that describes the interaction between the (1) gauge field and the charged complex scalar fields. The above 4D field theoretical model is considered on a (4,2)-dimensional supermanifold para- metrized by the ordinary four space-time variables (with = 0, 1, 2, 3) and a pair of Grassmannian variables and $\\bar{}$ (with $^{2} = \\bar{}^{2} = 0$, $\\bar{} + \\bar{} = 0$). Geometrically, the (anti-)BRST invariance is encoded in the translation of the super-Lagrangian density along the Grassmannian directions of the above supermanifold such that the outcome of this shift operation is zero.
The continuous tower of scalar fields as a system of interacting dark matter–dark energy
Paulo Santos
2016-01-01
This paper aims to introduce a new parameterisation for the coupling Q in interacting dark matter and dark energy models by connecting said models with the Continuous Tower of Scalar Fields model. Based upon the existence of a dark matter and a dark energy sectors in the Continuous Tower of Scalar Fields, a simplification is considered for the evolution of a single scalar field from the tower, validated in this paper. This allows for the results obtained with the Continuous Tower of Scalar Fi...
Potential-density pairs for axisymmetric galaxies: the influence of scalar fields
Rodriguez-Meza, M A; Cervantes-Cota, Jorge L.; Pedraza, M. I.; Tlapanco, J. F.; De la Calleja, E. M.
2005-01-01
We present a formulation for potential-density pairs to describe axisymmetric galaxies in the Newtonian limit of scalar-tensor theories of gravity. The scalar field is described by a modified Helmholtz equation with a source that is coupled to the standard Poisson equation of Newtonian gravity. The net gravitational force is given by two contributions: the standard Newtonian potential plus a term stemming from massive scalar fields. General solutions have been found for axisymmetric systems a...
Strong field gravitational lensing by a charged Galileon black hole
Zhao, Shan-Shan
2016-01-01
Strong field gravitational lensings are dramatically disparate from those in the weak field by representing relativistic images due to light winds one to infinity loops around a lens before escaping. We study such a lensing caused by a charged Galileon black hole, which is expected to have possibility to evade no-hair theorem. We calculate the angular separations and time delays between different relativistic images of the charged Galileon black hole. All these observables can potentially be used to discriminate a charged Galileon black hole from others. We estimate the magnitudes of the observables for the closest suppermassive black hole Sgr A*. It is found that when the scalar filed in the Galileon is weakly coupled to the gravitational field and it is "low-speed", the charged Galileon black hole can possibly be distinguished from a Reissner-Nordstr\\"om black hole.
Effective field theory of modified gravity with two scalar fields: dark energy and dark matter
Gergely, László Á
2014-01-01
We present a framework for discussing the cosmology of dark energy and dark matter based on two scalar degrees of freedom. An effective field theory of cosmological perturbations is employed. A unitary gauge choice renders the dark energy field into the gravitational sector, for which we adopt a generic Lagrangian depending on three-dimensional geometrical scalar quantities arising in the ADM decomposition. We add to this dark-energy associated gravitational sector a scalar field $\\phi$ and its kinetic energy $X$ as dark matter variables. Compared to the single-field case, we find that there are additional conditions to obey in order to keep the equations of motion for linear cosmological perturbations at second order. For such a second-order multi-field theory we derive conditions under which ghosts and Laplacian instabilities of the scalar and tensor perturbations are absent. We apply our general results to models with dark energy emerging in the framework of the Horndeski theory and dark matter described b...
Sadjadi, H Mohseni
2016-01-01
We study the parameterized post Newtonian approximation in teleparallel model of gravity with a scalar field. The scalar field is non-minimally coupled to the scalar torsion as well as to the boundary term introduced in [1]. We show that, in contrast to the case where the scalar field is only coupled to the scalar torsion, the presence of the new coupling affects the parameterized post Newtonian parameters. These parameters for different situations are obtained and discussed.
Quasiperiodical orbits in the scalar classical lambdaphi4 field theory
International Nuclear Information System (INIS)
New numerical and theoretical results of resonance kink-antikink (Kanti K) interactions in the classical one-dimentional space Higgs theory are presented. Earlier studies of these interactions revealed nine initial relative velocity-intervals with two-bounce Kanti K-collisions followed by the escape of kinks to infinite separations, the breathing solution was formed outside those intervals. Two-bounce Kanti K-interactions with the number of small oscillations between Kanti K-bounces up to 35 in the initial kink velocity interval 0.18 <= Vsub(infinite) <= 0.26 were found. Several examples for n-bounces Kanti K-interaction (n <= 6) are also found. The observed phenomenon can be explaned by the existence of quasi-two-periodical solutions of the nonlinear wave equation. The simple Hamiltonian with two degrees of freedom is studied. This model supplies quantitative descrtiptions of all numerical results for the field theory considered above. The considered phenomenon may be called ''autoquantization'' of a nonlinear classical scalar selfinteracting field
A flashless quantization of the scalar field on the "trousers"
Krasnikov, S
2016-01-01
The "trousers" spacetime is a pair of flat 2D cylinders ("legs") merging into into a single one ("trunk"). In spite of its simplicity this spacetime has a few features (including, in particular, a naked singularity in the "crotch") each of which is presumably unphysical, but for none of which a mechanism is known able to prevent its occurrence. Therefore it is interesting and important to study the behavior of the quantum fields in such a space. Anderson and DeWitt were the first to consider the free scalar field in the trousers spacetime. They argued that the crotch singularity produces an infinitely bright flash, which was interpreted as evidence that the topology of space is dynamically preserved. Similar divergencies were later discovered by Manogue, Copeland and Dray who used a more exotic quantization scheme. Later yet the same result obtained within a somewhat different approach led Sorkin to the conclusion that the topological transition in question is suppressed in quantum gravity. In this paper I sh...
Nonperturbative dynamics of scalar field theories through the Feynman-Schwinger representation
International Nuclear Information System (INIS)
A summary of results obtained for scalar field theories using the Feynman-Schwinger (FSR) approach is presented. Specifically, scalar QED and χ2φ theories are considered. The motivation behind the applications discussed in this paper is to use the FSR method as a rigorous tool for testing the quality of commonly used approximants in field theory
Casimir entropy and internal energy of the objects in fluctuating scalar and electromagnetic fields
Jafari, Marjan
2016-01-01
Casimir entropy is an important aspect of casimir effect.In this paper,we employ the path integral method to derive the total relation for casimir entropy and internal energy of arbitrary shaped objects in the presence of two,three and four dimensions scalar fields and electromagnetic field.We obtain the casimir entropy and internal energy of two nanoribbon immersed in scalar field and two nanospheres immersed in scalar field and electromagnetic field.The casmir entropy of two nanospheres immersed in the electromagnetic field in small interval of temperature variations,shown a different behavior.
Nucleon Scalar and Tensor Charges from Lattice QCD with Light Wilson Quarks
Green, J R; Pochinsky, A V; Syritsyn, S N; Engelhardt, M; Krieg, S
2012-01-01
We present 2+1 flavor Lattice QCD calculations of the nucleon scalar and tensor charges. Using the BMW clover-improved Wilson action with pion masses between 150 and 350 MeV and three source-sink separations between 0.9 and 1.4 fm, we achieve good control over excited-state contamination and extrapolation to the physical pion mass. As a consistency check, we also present results from calculations using unitary domain wall fermions with pion masses between 300 and 400 MeV, and using domain wall valence quarks and staggered sea quarks with pion masses between 300 and 600 MeV.
Gravitational Field of the Early Universe; 1, Non-linear Scalar Field as the Source
Chervon, S V
1997-01-01
In this review article we consider three most important sources of the gravitational field of the Early Universe: self-interacting scalar field, chiral field and gauge field. The correspondence between all of them are pointed out. More attention is payed to nonlinear scalar field source of gravity. The progress in finding the exact solutions in inflationary universe is reviewed. The basic idea of `fine turning of the potential' method is discussed and computational background is presented in details. A set of new exact solutions for standard inflationary model and conformally-flat space-times are obtained. Special attention payed to relations between `fine turning of the potential' and Barrow's approaches. As the example of a synthesis of both methods new exact solution is obtained.
Gravitational collapse of massless scalar field in $f(R)$ gravity
Zhang, Cheng-Yong; Wang, Bin
2016-01-01
We study the spherically symmetric gravitational collapse of massless scalar matter field in asymptotic flat spacetime in $f(R)$ gravity. In the Einstein frame of $f(R)$ gravity, an additional scalar field arises due to the conformal transformation. We find that besides the usual competition between gravitational energy and kinetic energy in the process of gravitational collapse, the new scalar field brought by the conformal transformation adds one more competing force in the dynamical system. The dynamical competition can be controlled by tuning the amplitudes of the initial perturbations of the new scalar field and the matter field. To understand the physical reasons behind these phenomena, we analyze the gravitational potential behavior and calculate the Ricci scalar at center with the change of initial amplitudes of perturbations. We find rich physics on the formation of black holes through gravitational collapse in $f(R)$ gravity.
The continuous tower of scalar fields as a system of interacting dark matter–dark energy
Directory of Open Access Journals (Sweden)
Paulo Santos
2015-10-01
Full Text Available This paper aims to introduce a new parameterisation for the coupling Q in interacting dark matter and dark energy models by connecting said models with the Continuous Tower of Scalar Fields model. Based upon the existence of a dark matter and a dark energy sectors in the Continuous Tower of Scalar Fields, a simplification is considered for the evolution of a single scalar field from the tower, validated in this paper. This allows for the results obtained with the Continuous Tower of Scalar Fields model to match those of an interacting dark matter–dark energy system, considering that the energy transferred from one fluid to the other is given by the energy of the scalar fields that start oscillating at a given time, rather than considering that the energy transference depends on properties of the whole fluids that are interacting.
The Continuous Tower of Scalar Fields as a System of Interacting Dark Matter -- Dark Energy
Santos, Paulo
2015-01-01
This paper aims to introduce a new parameterisation for the coupling Q in interacting dark matter and dark energy models by connecting said models with the Continuous Tower of Scalar Fields model. Based upon the existence of a dark matter and a dark energy sectors in the Continuous Tower of Scalar Fields, a simplification is considered for the evolution of a single scalar field from the tower, validated in this paper. This allows for the results obtained with the Continuous Tower of Scalar Fields model to match those of an interacting dark matter - dark energy system, considering that the energy transferred from one fluid to the other is given by the energy of the scalar fields that start oscillating at a given time, rather than considering that the energy transference depends on properties of the whole fluids that are interacting.
The continuous tower of scalar fields as a system of interacting dark matter-dark energy
Santos, Paulo
2015-10-01
This paper aims to introduce a new parameterisation for the coupling Q in interacting dark matter and dark energy models by connecting said models with the Continuous Tower of Scalar Fields model. Based upon the existence of a dark matter and a dark energy sectors in the Continuous Tower of Scalar Fields, a simplification is considered for the evolution of a single scalar field from the tower, validated in this paper. This allows for the results obtained with the Continuous Tower of Scalar Fields model to match those of an interacting dark matter-dark energy system, considering that the energy transferred from one fluid to the other is given by the energy of the scalar fields that start oscillating at a given time, rather than considering that the energy transference depends on properties of the whole fluids that are interacting.
Cosmological perturbations in SFT inspired non-local scalar field models
International Nuclear Information System (INIS)
We study cosmological perturbations in models with a single non-local scalar field originating from the string field theory description of the rolling tachyon dynamics. We construct the equation for the energy density perturbations of the non-local scalar field and explicitly prove that for the free field it is identical to a system of local cosmological perturbation equations in a particular model with multiple (maybe infinitely many) local free scalar fields. We also show that vector and tensor perturbations are absent in this set-up. (orig.)
Thermodynamics of Lovelock black holes with a nonminimal scalar field
Energy Technology Data Exchange (ETDEWEB)
Correa, Francisco [Centro de Estudios Científicos (CECs),Valdivia (Chile); Hassaine, Mokhtar [Instituto de Matemática y Física, Universidad de Talca,Casilla 747, Talca (Chile)
2014-02-04
We source the Lovelock gravity theories indexed by an integer k and fixed by requiring a unique anti-de Sitter vacuum with a self-interacting nonminimal scalar field in arbitrary dimension d. For each inequivalent Lovelock gravity theory indexed by the integer k, we establish the existence of a two-parametric self-interacting potential that permits to derive a class of black hole solutions with planar horizon for any arbitrary value of the nonminimal coupling parameter. In the thermodynamical analysis of the solution, we show that, once regularized the Euclidean action, the mass contribution coming form the gravity side exactly cancels, order by order, the one arising from the matter part yielding to a vanishing mass. This result is in accordance with the fact that the entropy of the solution, being proportional to the lapse function evaluated at the horizon, also vanishes. Consequently, the integration constant appearing in the solution is interpreted as a sort of hair which turns out to vanish at high temperature.
Localization of gravity on a thick braneworld without scalar fields
Herrera-Aguilar, Alfredo; Mora-Luna, Refugio Rigel
2010-01-01
In this work we present a simple thick braneworld model that is generated by an intriguing interplay between a 5D cosmological constant with a de Sitter metric induced in the 3-brane without the inclusion of scalar fields. We show that 4D gravity is localized on this brane, provide analytic expressions for the massive Kaluza-Klein (KK) fluctuation modes and also show that the spectrum of metric excitations displays a mass gap. We finally present the corrections to Newton's law due to these massive modes. This model has no naked singularities along the fifth dimension despite the existence of a mass gap in the graviton spectrum as it happens in thick branes with 4D Poincare symmetry, providing a simple model with very good features: the curvature is completely smooth along the fifth dimension, it localizes 4D gravity and the spectrum of gravity fluctuations presents a mass gap, a fact that rules out the existence of phenomenologically dangerous ultralight KK excitations in the model.
Thermodynamics of Lovelock black holes with a nonminimal scalar field
Correa, Francisco
2013-01-01
We source the Lovelock gravity theories indexed by an integer k and fixed by requiring a unique anti-de Sitter vacuum with a self-interacting nonminimal scalar field in arbitrary dimension d. For each inequivalent Lovelock gravity theory indexed by the integer k, we establish the existence of a two-parametric self-interacting potential that permits to derive a class of black hole solutions with planar horizon for any arbitrary value of the nonminimal coupling parameter. In the thermodynamical analysis of the solution, we show that, once regularized the Euclidean action, the mass contribution coming form the gravity side exactly cancels, order by order, the one arising from the matter part yielding to a vanishing mass. This result is in accordance with the fact that the entropy of the solution, being proportional to the lapse function evaluated at the horizon, also vanishes. Consequently, the integration constant appearing in the solution is interpreted as a sort of hair which turns out to vanish at high tempe...
Cosmological perturbations in coherent oscillating scalar field models
Cembranos, J. A. R.; Maroto, A. L.; Jareño, S. J. Núñez
2016-03-01
The fact that fast oscillating homogeneous scalar fields behave as perfect fluids in average and their intrinsic isotropy have made these models very fruitful in cosmology. In this work we will analyse the perturbations dynamics in these theories assuming general power law potentials V( ϕ) = λ| ϕ| n /n. At leading order in the wavenumber expansion, a simple expression for the effective sound speed of perturbations is obtained c eff 2 = ω = ( n - 2)/( n + 2) with ω the effective equation of state. We also obtain the first order correction in k 2/ ω eff 2 , when the wavenumber k of the perturbations is much smaller than the background oscillation frequency, ω eff. For the standard massive case we have also analysed general anharmonic contributions to the effective sound speed. These results are reached through a perturbed version of the generalized virial theorem and also studying the exact system both in the super-Hubble limit, deriving the natural ansatz for δϕ; and for sub-Hubble modes, exploiting Floquet's theorem.
Cosmological perturbations in coherent oscillating scalar field models
Cembranos, J A R; Jareño, S J Núñez
2015-01-01
The fact that fast oscillating homogeneous scalar fields behave as perfect fluids in average and their intrinsic isotropy have made these models very fruitful in cosmology. In this work we will analyse the perturbations dynamics in these theories assuming general power law potentials $V(\\phi)=\\lambda \\vert\\phi\\vert^{n}/n$. At leading order in the wavenumber expansion, a simple expression for the effective sound speed of perturbations is obtained $c_{\\text{eff}}^2 = \\omega=(n-2)/(n+2)$ with $\\omega$ the effective equation of state. We also obtain the first order correction in $k^2/\\omega_{\\text{eff}}^2$, when the wavenumber $k$ of the perturbations is much smaller than the background oscillation frequency, $\\omega_{\\text{eff}}$. For the standard massive case we have also analysed general anharmonic contributions to the effective sound speed. These results are reached through a perturbed version of the generalized virial theorem and also studying the exact system both in the super-Hubble limit, deriving the nat...
Spikes and matter inhomogeneities in massless scalar field models
Coley, Alan
2015-01-01
We shall discuss the general relativistic generation of spikes in a massless scalar field or stiff perfect fluid model. We first investigate orthogonally transitive (OT) $G_2$ stiff fluid spike models both heuristically and numerically, and give a new exact OT $G_2$ stiff fluid spike solution. We then present a new two-parameter family of non-OT $G_2$ stiff fluid spike solutions, obtained by the generalization of non-OT $G_2$ vacuum spike solutions to the stiff fluid case by applying Geroch's transformation on a Jacobs seed. The dynamics of these new stiff fluid spike solutions is qualitatively different from that of the vacuum spike solutions, in that the matter (stiff fluid) feels the spike directly and the stiff fluid spike solution can end up with a permanent spike. We then derive the evolution equations of non-OT $G_2$ stiff fluid models, including a second perfect fluid, in full generality, and briefly discuss some of their qualitative properties and their potential numerical analysis. Finally, we discu...
Electric charge in the stochastic electric field
Simonov, Yu A
2016-01-01
The influence of electric stochastic fields on the relativistic charged particles is investigated in the gauge invariant path integral formalism. Using the cumulant expansion one finds the exponential relaxation of the charge Green's function both for spinless and Dirac charges.
Inflation and the semiclassical dynamics of a conformal scalar field
International Nuclear Information System (INIS)
We derive the semiclassical evolution of massless conformally coupled scalar matter in the de Sitter space-time from the Born-Oppenheimer reduction of the Wheeler-DeWitt equation. We find a remarkable difference with respect to the minimally coupled case: the effect of the quantum gravitational corrections does not depend on the momentum of the scalar mode up to second order in the Planck length and, therefore, there are no relevant corrections to the dispersion relation
Cosmological dynamics of scalar field with non-minimal kinetic term
Kröger, H; Melkonyan, G.; Rubin, S. G.
2003-01-01
We investigate dynamics of scalar field with non-minimal kinetic term. Nontrivial behavior of the field in the vicinity of singular points of kinetic term is observed. In particular, the singular points could serve as attractor for classical solutions.
Conversions of Bound Muons: Lepton Flavour Violation from Doubly Charged Scalars
Geib, Tanja
2015-01-01
We present the first detailed computation of the conversion of a bound muon into an electron mediated by a doubly charged $SU(2)$ singlet scalar. Although such particles are not too exotic, up to now their contribution to $\\mu$-$e$ conversion is unknown. We close this gap by presenting a detailed calculation, which will allow the reader not only to fully comprehend the discussion but also to generalise our results to similar cases if needed. We furthermore compare the predictions, for both the general case and for an example model featuring a neutrino mass at 2-loop level, to current experimental data and future sensitivities. We show that, depending on the explicit values of the couplings as well as on the actual future limits on the branching ratio, $\\mu$-$e$ conversion may potentially yield a lower limit on the doubly charged singlet scalar mass which is stronger than what could be obtained by colliders. Our results considerably strengthen the case for low-energy lepton flavour violation searches being a v...
Conversions of bound muons: Lepton flavor violation from doubly charged scalars
Geib, Tanja; Merle, Alexander
2016-03-01
We present the first detailed computation of the conversion of a bound muon into an electron mediated by a doubly charged S U (2 ) singlet scalar. Although such particles are not too exotic, up to now their contribution to μ -e conversion is unknown. We close this gap by presenting a detailed calculation, which will allow the reader not only to fully comprehend the discussion but also to generalize our results to similar cases if needed. We furthermore compare the predictions, for both the general case and an example model featuring a neutrino mass at two-loop level, to current experimental data and future sensitivities. We show that, depending on the explicit values of the couplings as well as on the actual future limits on the branching ratio, μ -e conversion may potentially yield a lower limit on the doubly charged singlet scalar mass, which is stronger than what could be obtained by colliders. Our results considerably strengthen the case for low-energy lepton flavor violation searches being a very valuable addition to collider experiments.
Neutron star mass-radius relation with gravitational field shielding by a scalar field
Institute of Scientific and Technical Information of China (English)
Bo-Jun Zhang; Tian-Xi Zhang; Padmaja Guggilla; Mostafa Dokhanian
2013-01-01
The currently well-developed models for equations of state (EoSs) have been severely impacted by recent measurements of neutron stars with a small radius and/or large mass.To explain these measurements,the theory of gravitational field shielding by a scalar field is applied.This theory was recently developed in accordance with the five-dimensional (5D) fully covariant Kaluza-Klein (KK) theory that has successfully unified Einstein's general relativity and Maxwell's electromagnetic theory.It is shown that a massive,compact neutron star can generate a strong scalar field,which can significantly shield or reduce its gravitational field,thus making it more massive and more compact.The mass-radius relation developed under this type of modified gravity can be consistent with these recent measurements of neutron stars.In addition,the effect of gravitational field shielding helps explain why the supernova explosions of some very massive stars (e.g.,40 M⊙ as measured recently) actually formed neutron stars rather than black holes as expected.The EoS models,ruled out by measurements of small radius and/or large mass neutron stars according to the theory of general relativity,can still work well in terms of the 5D fully covariant KK theory with a scalar field.
Can the Big Bang singularity be avoided by a single scalar field?
International Nuclear Information System (INIS)
In this paper, we investigate the possibility of avoiding the Big Bang singularity with a single scalar field which couples non-minimally to gravity. We show that in the case when gravity couples linearly to the field, some severe conditions on the field's potential have to be imposed. However, in the nonlinear case, it is quite generic to avoid the singularity with the single scalar field.
Thermodynamics of hot quantum scalar field in a (D+1) dimensional curved spacetime
C., W A Rojas
2016-01-01
We use the brick wall model to calculate the free energy of quantum scalar field in a curved spacetime (D +1) dimensions. We find the thermodynamics properties of quantum scalar field in several scenaries: Minkowski spacetime, Schwarzschild spacetime and BTZ spacetime. For the cases analysed, the thermodynamical properties of quantum scalar field is exactly with the reported. It was found that the entropy of the gas is proportional to the horizon area in a gravity field strong, which is consistent with the holographic principle.
Brane structure and metastable graviton in five-dimensional model with (non)canonical scalar field
Zhong, Yuan; Zhao, Zhen-Hua
2014-01-01
The appearance of inner brane structure is an interesting issue in domain wall {brane model}. Because such structure usually leads to quasilocalized modes of various kinds of bulk fields. In this paper, we construct a domain wall brane model by using a scalar field $\\phi$, which couples to its kinetic term. The inner brane structure emerges as the scalar-kinetic coupling increases. With such brane structure, we show that it is possible to obtain gravity resonant modes in both tensor and scalar sectors. The number of the resonant modes depends on the vacuum expectation value of $\\phi$ and the form of scalar-kinetic coupling. The correspondence between our model and the canonical one is also discussed. The noncanonical and canonical background scalar fields are connected by an integral equation, while the warp factor remains the same. Via this correspondence, the canonical and noncanonical models share the same linear perturbation spectrum. So the gravity resonances {obtained} in the noncanonical frame can also...
On the relativistic quantum mechanics of scalar field
International Nuclear Information System (INIS)
The relativistic quantum mechanics of a complex field has been developed in the framework of which in an explicit form in the expressions for charge Q and momentum Psup(j) of the field there are considered the terms taking into account the relativity of simultaneity and depending on current density and four-momentum density, respectively. The expressions for Q and Psup(i), obtained in the momentum space, coincide with the conventional ones. The relativistic position operator x1 is introduced that has the same form as for a non-relativistic approximation. The relativistic analogues of the Ehrenfest theorems are derived. The relativistic invariant definition is given for a three-dimensional delta-function
Foot, Robert
2016-01-01
We argue that a charged scalar particle $\\chi$ of mass around 375 GeV charged under both $\\mathrm{SU}(3)_{c}$ and a new confining non-abelian gauge interaction can explain the 750 GeV diphoton excess. After pair production, these interactions confine the exotic scalar into non-relativistic bound states whose decays into photons can explain the discrepancy. Taking the new confining group to be $\\mathrm{SU}(2)$, we find $\\chi$ must carry an electric charge of $Q \\approx 1/2$ to fit the data. Interestingly, we find that pair production of the scalars and the subsequent formation of the bound state dominates over direct bound state resonance production. This explanation is quite weakly constrained by current experimental bounds, and we expect future constraints to come from dijet, mono-jet and possibly dilepton searches.
Transport equation for the time scale of a turbulent scalar field
International Nuclear Information System (INIS)
The two-parametric turbulence models cause serious difficulties by modeling the near-wall flows due to absence of the natural boundary condition on the wall for dissipation of the ε turbulence energy and the εθ scalar field destruction. This difficulty may be overcome, if instead of the ε and εθ, as the second parameter of the model, to apply the time scales of the turbulent dynamic and scalar fields. The equation of the scalar field is derived and numerical coefficients included therein, are determined from the simplest problems on the turbulent heat transfer
Olabarrieta, I.; Ventrella, J.; Choptuik, M.; Unruh, W.
2007-01-01
We study the critical collapse of a massless scalar field with angular momentum in spherical symmetry. In order to mimic the effects of angular momentum we perform a sum of the stress-energy tensors for all the scalar fields with the same eigenvalue, l, of the angular momentum operator and calculate the equations of motion for the radial part of these scalar fields. We have found that the critical solutions for different values of l are discretely self-similar (as in the original l=0 case). T...
Difficulty of a spinning complex scalar field to be dark energy
Kasuya, S.
2001-01-01
We comment on the possibility of a spinning complex scalar field to be dark energy. We show that it deforms (almost) completely into a nontopological soliton state, a Q ball, and the equation of state becomes that of the matter or radiation, depending on the fate of the Q ball. Thus, the spinning complex scalar field is usually very difficult to play the role of the dark energy. We also show the general condition that the spinning complex scalar field can successfully be the dark energy.
The Hamiltonian formalism for scalar fields coupled to gravity in a cosmological background
Energy Technology Data Exchange (ETDEWEB)
Bernardini, A.E., E-mail: alexeb@ufscar.br; Bertolami, O., E-mail: orfeu.bertolami@fc.up.pt
2013-11-15
A novel routine to investigate the scalar fields in a cosmological context is discussed in the framework of the Hamiltonian formalism. Starting from the Einstein–Hilbert action coupled to a Lagrangian density that contains two components–one corresponding to a scalar field Lagrangian, L{sub ϕ}, and another that depends on the scale parameter, L{sub a}–one can identify a generalized Hamiltonian density from which first-order dynamical equations can be obtained. This set up corresponds to the dynamics of Friedmann–Robertson–Walker models in the presence of homogeneous fields embedded into a generalized cosmological background fluid in a system that evolves all together isentropically. Once the generalized Hamiltonian density is properly defined, the constraints on the gravity–matter–field system are straightforwardly obtained through the first-order Hamilton equations. The procedure is illustrated for three examples of cosmological interest for studies of the dark sector: real scalar fields, tachyonic fields and generalized Born–Infeld tachyonic fields. The inclusion of some isentropic fluid component into the Friedmann equation allows for identifying an exact correspondence between the dark sector underlying scalar field and an ordinary real scalar field dynamics. As a final issue, the Hamiltonian formulation is used to set the first-order dynamical equations through which one obtains the exact analytical description of the cosmological evolution of a generalized Chaplygin gas (GCG) with dustlike matter, radiation or curvature contributions. Model stability in terms of the square of the sound velocity, c{sub s}{sup 2}, cosmic acceleration, q, and conditions for inflation are discussed. -- Highlights: •The Hamiltonian formalism for scalar fields coupled to gravity in a cosmological background is constructed. •Real scalar, tachyonic and generalized Born–Infeld tachyonic-type fields are considered. •An extended formulation of the Hamilton
Quantum and classical aspects of scalar and vector fields around black holes
Wang, Mengjie
2016-01-01
This thesis presents recent studies on test scalar and vector fields around black holes. It is separated in two parts according to the asymptotic properties of the spacetime under study. In the first part, we investigate scalar and Proca fields on an asymptotically flat background. For the Proca field, we obtain a complete set of equations of motion in higher dimensional spherically symmetric backgrounds. These equations are solved numerically, both to compute Hawking radiation spectra and qu...
Casimir Effect of Massive Scalar Field with Hybrid Boundary Condition in (1+1)-Dimensional Spacetime
Institute of Scientific and Technical Information of China (English)
HE Xiao-Kai; LIU Wen-Biao; QIU Wei-Gang
2009-01-01
The Casimir energy of maesive scalar field with hybrid (Dirichlet-Neumann) boundary condition is calcu-lated. In order to regularize the model, the typical methods named as mode summation method and Green's function method are used respectively. It is found that the regularized zero-point energy density depends on the scalar field's mass. When the field is massless, the result is consistent with previous literatures.
Cosmological evolution of a complex scalar field with repulsive or attractive self-interaction
Suárez, Abril
2016-01-01
We study the cosmological evolution of a complex scalar field with a self-interaction potential $V(|\\varphi|^2)$, possibly describing self-gravitating Bose-Einstein condensates, using a fully general relativistic treatment. We generalize the hydrodynamic representation of the Klein-Gordon-Einstein equations in the weak field approximation developed in our previous paper. We establish the general equations governing the evolution of a spatially homogeneous complex scalar field in an expanding background. We show how they can be simplified in the fast oscillation regime and derive the equation of state of the scalar field in parametric form for an arbitrary potential. We explicitly consider the case of a quartic potential with repulsive or attractive self-interaction and determine the phase diagram of the scalar field. We show that the transition between the weakly self-interacting regime and the strongly self-interacting regime depends on how the scattering length of the bosons compares with their effective Sc...
Besprosvany, J
2002-01-01
Unification ideas motivate the formulation of field equations on an extended spin space. Demanding that the Poincare symmetry be maintained, one derives scalar symmetries that are associated with flavor and gauge groups. Boson and fermion solutions are obtained with a fixed representation. A field theory can be equivalently written and interpreted in terms of elements of such space and is similarly constrained. At 5+1 dimensions, one obtains isospin and hypercharge SU(2)_L X U(1) symmetries, their vector carriers, two-flavor charged and chargeless leptons, and scalar particles. Mass terms produce breaking of the symmetry to an electromagnetic U(1), a Weinberg's angle with sin^2(theta_W)=.25, and additional information on the respective coupling constants. Their underlying spin symmetry gives information on the particles' masses; one reproduces the standard-model ratio M_Z/M_W, and predicts a Higgs mass of M_H ~114 GeV, at tree level.
A unified optical theorem for scalar and vectorial wave fields
Wapenaar, C.P.A.; Douma, H.
2012-01-01
The generalized optical theorem is an integral relation for the angle-dependent scattering amplitude of an inhomogeneous scattering object embedded in a homogeneous background. It has been derived separately for several scalar and vectorial wave phenomena. Here a unified optical theorem is derived t
A late time accelerated FRW model with scalar and vector fields via Noether symmetry
Directory of Open Access Journals (Sweden)
Babak Vakili
2014-11-01
Full Text Available We study the evolution of a three-dimensional minisuperspace cosmological model by the Noether symmetry approach. The phase space variables turn out to correspond to the scale factor of a flat Friedmann–Robertson–Walker (FRW model, a scalar field with potential function V(ϕ with which the gravity part of the action is minimally coupled and a vector field of its kinetic energy is coupled with the scalar field by a coupling function f(ϕ. Then, the Noether symmetry of such a cosmological model is investigated by utilizing the behavior of the corresponding Lagrangian under the infinitesimal generator of the desired symmetry. We explicitly calculate the form of the coupling function between the scalar and the vector fields and also the scalar field potential function for which such symmetry exists. Finally, by means of the corresponding Noether current, we integrate the equations of motion and obtain exact solutions for the scale factor, scalar and vector fields. It is shown that the resulting cosmology is an accelerated expansion universe for which its expansion is due to the presence of the vector field in the early times, while the scalar field is responsible of its late time expansion.
Kalinichenko, I S
2016-01-01
The explicit expressions for the high-temperature expansions of the one-loop corrections to the omega-potential coming from the charged scalar and Dirac particles and, separately, from antiparticles in a constant homogeneous magnetic field are derived. The explicit expressions for the non-perturbative corrections to the effective action at finite temperature and density are obtained. The thermodynamic properties of a gas of charged scalars in a constant homogeneous magnetic field are analyzed in the one-loop approximation. It turns out that, in this approximation, the system suffers the first order phase transition from the diamagnetic to the superconducting state at sufficiently high densities. The improvement of the one-loop result by summing the ring diagrams is investigated. This improvement leads to a drastic change of the thermodynamic properties of the system. The gas of charged scalars passes to the ferromagnetic state in place of the superconducting one at high densities and sufficiently low temperat...
Quasi-stationary solutions of self-gravitating scalar fields around black holes
Sanchis-Gual, Nicolas; Montero, Pedro J; Font, José A
2014-01-01
Recent perturbative studies have shown the existence of long-lived, quasi-stationary configurations of scalar fields around black holes. In particular, such configurations have been found to survive for cosmological timescales, which is a requirement for viable dark matter halo models in galaxies based on such type of structures. In this paper we perform a series of numerical relativity simulations of dynamical non-rotating black holes surrounded by self-gravitating scalar fields. We solve numerically the coupled system of equations formed by the Einstein and the Klein-Gordon equations under the assumption of spherical symmetry using spherical coordinates. Our results confirm the existence of oscillating, long-lived, self-gravitating scalar fields configurations around non-rotating black holes in highly dynamical spacetimes with a rich scalar field environment. Our numerical simulations are long-term stable and allow for the extraction of the resonant frequencies to make a direct comparison with results obtai...
Correspondence of f(R,∇R) Modified Gravity with Scalar Field Models
International Nuclear Information System (INIS)
This paper is devoted to study the scalar field dark energy models by taking its different aspects in the framework of f(R,∇R) gravity. We consider flat FRW universe to construct the equation of state parameter governed by f(R,∇R) gravity. The stability of the model is discussed with the help of squared speed of sound parameter. It is found that models show quintessence behavior of the universe in stable as well as unstable modes. We also develop the correspondence of f(R,∇R) model with some scalar field dark energy models like quintessence, tachyonic field, k-essence, dilaton, hessence, and DBI-essence. The nature of scalar fields and corresponding scalar potentials is being analyzed in f(R,∇R) gravity graphically which show consistency with the present day observations about accelerated phenomenon
New class of cosmological solutions for a self-interacting scalar field
Chaadaev, A. A.; Chervon, S. V.
2013-12-01
New cosmological solutions are found to the system of Einstein scalar field equations using the scalar field φ as the argument. For a homogeneous and isotropic Universe, the system of equations is reduced to two equations, one of which is an equation of Hamilton-Jacobi type. Using the hyperbolically parameterized representation of this equation together with the consistency condition, explicit dependences of the potential V of the scalar field and the Hubble parameter H on φ are obtained. The dependences of the scalar field and the scale factor a on cosmic time t have also been found. It is shown that this scenario corresponds to the evolution of the Universe with accelerated expansion out to times distant from the initial singularity.
Quasistationary solutions of self-gravitating scalar fields around collapsing stars
Sanchis-Gual, Nicolas; Montero, Pedro J; Font, José A; Mewes, Vassilios
2015-01-01
Recent work has shown that scalar fields around black holes can form long-lived, quasistationary configurations surviving for cosmological timescales. With this requirement, scalar fields cannot be discarded as viable candidates for dark matter halo models in galaxies around central supermassive black holes (SMBH). One hypothesis for the formation of most SMBHs at high redshift is the gravitational collapse of supermassive stars (SMS) with masses of $\\sim10^5 \\rm {M_{\\odot}}$. Therefore, a constraint for the existence of quasi-bound states of scalar fields is their survival to such dynamic events. To answer this question we present in this paper the results of a series of numerical relativity simulations of gravitationally collapsing, spherically symmetric stars surrounded by self-gravitating scalar fields. We use an ideal fluid equation of state with adiabatic index $\\Gamma=4/3$ which is adequate to simulate radiation-dominated isentropic SMSs. Our results confirm the existence of oscillating, long-lived, se...
A generalisation of classical electrodynamics for the prediction of scalar field effects
van Vlaenderen, K J
2003-01-01
Within the framework of Classical Electrodynamics (CED) it is common practice to choose freely an arbitrary gauge condition with respect to a gauge transformation of the electromagnetic potentials. The Lorenz gauge condition allows for the derivation of the inhomogeneous potential wave equations (IPWE), but this also means that scalar derivatives of the electromagnetic potentials are considered to be \\emph{unphysical}. However, these scalar expressions might have the meaning of a new physical field, $\\mathsf S$. If this is the case, then a generalised CED is required such that scalar field effects are predicted and such that experiments can be performed in order to verify or falsify this generalised CED. The IPWE are viewed as a generalised Gauss law and a generalised Ampe\\`re law, that also contain derivatives of $\\mathsf S$, after reformulating the IPWE in terms of fields. Some recent experiment show positive results that are in qualitative agreement with the presented predictions of scalar field effects, b...
On localization of universal scalar fields in a tachyonic de Sitter thick braneworld
Diaz-Furlong, Alfonso; Linares, Roman; Mora-Luna, Refugio Rigel; Morales-Tecotl, Hugo A
2014-01-01
Braneworld models may yield interesting effects ranging from high-energy physics to cosmology, or even some low-energy physics. Their mode structure modifies standard results in these physical realms that can be tested and used to set bounds on the models parameters. Now, to define braneworld deviations from standard 4D physics, a notion of matter and gravity localization on the brane is crucial. In this work we investigate the localization of universal massive scalar fields in a de Sitter thick tachyonic braneworld generated by gravity coupled to a tachyonic bulk scalar field. This braneworld possesses a 4D de Sitter induced metric and is asymptotically flat despite the presence of a negative bulk cosmological constant, a novel and interesting peculiarity that contrasts with previously known models. Universal scalar fields can be localized in this expanding braneworld if their bulk mass obeys an upper bound, otherwise they delocalize: The dynamics of the scalar field is governed by a Schroedinger equation wi...
Perturbative self-interacting scalar field theory: a differential equation approach
Rocha, R; Coimbra-Araujo, C H
2005-01-01
We revisit the investigation about the partition function related to a \\phi^4-scalar field theory on a n-dimensional Minkowski spacetime, which is shown to be a self-interacting scalar field theory at least in 4-dimensional Minkowski spacetime. After rederiving the analytical calculation of the perturbative expansion coefficients and also the approximate values for suitable limits using Stirling's formulae, which consists of Witten's proposed questions, solved by P. Deligne, D. Freed, L. Jeffrey, and S. Wu, we investigate a spherically symmetric scalar field in a n-dimensional Minkowski spacetime. For the first perturbative expansion coefficient it is shown how it can be derived a modified Bessel equation (MBE), which solutions are investigated in one, four, and eleven-dimensional Minkowski spacetime. The solutions of MBE are the first expansion coefficient of the series associated with the partition function of \\phi^4-scalar field theory.
Scalar fields in Kasner-type space-times: Time dependent vacuum expectation values
International Nuclear Information System (INIS)
Non-constant vacuum expectation values of scalar fields in curved space-times generate important physical consequences. It is here shown this to be the case for a class of spatially homogeneous and anisotropic metrics. (Author)
Entropy-corrected holographic scalar field models of dark energy in Kaluza-Klein universe
Sharif, M.; Jawad, Abdul
2013-12-01
We investigate the evolution of interacting holographic dark energy with logarithmic corrections in the flat Kaluza-Klein universe. We evaluate the equation of state parameter and also reconstruct the scalar field models in this scenario. For this purpose, the well-known choice of scale factor in the power law form is taken. It is interesting to mention here that the corresponding equation of state parameter crosses the phantom divide line for a particular choice of interacting parameters. Finally, we conclude that the behavior of the dynamical scalar field as well as the scalar potential is consistent with the present observations.
Dressing a black hole with non-minimally coupled scalar field hair
Winstanley, Elizabeth(Consortium for Fundamental Physics, School of Mathematics and Statistics, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH, United Kingdom)
2005-01-01
We investigate the possibility of dressing a four-dimensional black hole with classical scalar field hair which is non-minimally coupled to the space-time curvature. Our model includes a cosmological constant but no self-interaction potential for the scalar field. We are able to rule out black hole hair except when the cosmological constant is negative and the constant governing the coupling to the Ricci scalar curvature is positive. In this case, non-trivial hairy black hole solutions exist,...
International Nuclear Information System (INIS)
Brane world models with a nonminimally coupled bulk scalar field have been studied recently. In this paper we consider metric fluctuations around an arbitrary gravity-scalar background solution, and we show that the corresponding spectrum includes a localized zero mode which strongly depends on the profile of the background scalar field. For a special class of solutions, with a warp factor of the RS form, we solve the linearized Einstein equations, for a pointlike mass source on the brane, by using the brane bending formalism. We see that general relativity on the brane is recovered only if we impose restrictions on the parameter space of the models under consideration
Formation of Schwarzschild black hole from the scalar field collapse in four-dimensions
Oliveira-Neto, G.; Takakura, F. I.
2003-01-01
We obtain a new self-similar solution to the Einstein's equations in four-dimensions, representing the collapse of a spherically symmetric, minimally coupled, massless, scalar field. Depending on the value of certain parameters, this solution represents the formation of naked singularities and black holes. Since the black holes are identified as the Schwarzschild ones, one may naturally see how these black holes are produced as remnants of the scalar field collapse.
Directory of Open Access Journals (Sweden)
Kazuharu Bamba
2014-10-01
Full Text Available We reconstruct scalar field theories to realize inflation compatible with the BICEP2 result as well as the Planck. In particular, we examine the chaotic inflation model, natural (or axion inflation model, and an inflationary model with a hyperbolic inflaton potential. We perform an explicit approach to find out a scalar field model of inflation in which any observations can be explained in principle.
Interacting entropy-corrected holographic scalar field models in non-flat universe
Khodam-Mohammadi, A
2010-01-01
we establish the correspondence between the tachyon, K-essence and dilaton scalar field models with the interacting entropy-corrected holographic dark energy model (ECHDE) in non-flat FRW universe. We reconstruct the potentials and the dynamics of these scalar fields according to the evolutionary behavior of the interacting ECHDE model. The results of interacting ECHDE model reduce to those obtained from the limiting case HDE without entropy-correction.
QCD phase transition with a power law chameleon scalar field in the bulk
Golanbari, T.; Mohammadi, A.; Saaidi, Kh.
2014-01-01
In this work, a brane world model with a perfect fluid on brane and a scalar field on bulk has been used to study quark-hadron phase transition. The bulk scalar field has an interaction with brane matter. This interaction comes into non-conservation relation which describe an energy transfer between bulk and brane. Since quark-hadron transition curly depends on the form of evolution equations therefore modification of energy conservation equation and Friedmann equation comes into some interes...
Wheeler-DeWitt equation and Lie symmetries in Bianchi scalar-field cosmology
Energy Technology Data Exchange (ETDEWEB)
Paliathanasis, A. [Universidad Austral de Chile, Instituto de Ciencias Fisicas y Matematicas, Valdivia (Chile); Karpathopoulos, L. [University of Athens, Faculty of Physics, Department of Astronomy-Astrophysics-Mechanics, Athens (Greece); Wojnar, A. [Institute for Theoretical Physics, Wroclaw (Poland); Universita' di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Dipartimento di Fisica ' ' E. Pancini' ' , Naples (Italy); Complesso Universitario di Monte S. Angelo, Naples (Italy); Istituto Nazionale di Fisica Nucleare (INFN) Sez. di Napoli, Naples (Italy); Capozziello, S. [Universita' di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Dipartimento di Fisica ' ' E. Pancini' ' , Naples (Italy); Complesso Universitario di Monte S. Angelo, Naples (Italy); Gran Sasso Science Institute (INFN), L' Aquila (Italy); Istituto Nazionale di Fisica Nucleare (INFN) Sez. di Napoli, Naples (Italy)
2016-04-15
Lie symmetries are discussed for the Wheeler-De Witt equation in Bianchi Class A cosmologies. In particular, we consider general relativity, minimally coupled scalar-field gravity and hybrid gravity as paradigmatic examples of the approach. Several invariant solutions are determined and classified according to the form of the scalar-field potential. The approach gives rise to a suitable method to select classical solutions and it is based on the first principle of the existence of symmetries. (orig.)
Note on the thermodynamics and the speed of sound of a scalar field
International Nuclear Information System (INIS)
We investigate the correspondence between a perfect fluid and a scalar field and show a possible way of expressing thermodynamic quantities such as entropy, particle number density, temperature and chemical potential in terms of the scalar field ϕ and its kinetic term X. We prove a theorem which relates isentropy with purely kinetic Lagrangian. As an application, we study the evolution of the gravitational potential in cosmological perturbation theory. (paper)
Evolution of spherical over-densities in tachyon scalar field model
Setare, M R; Darabi, F
2016-01-01
We study the tachyon scalar field model in flat FRW cosmology with the scale factor behavior $a(t)=t^n$. We consider the spherical collapse model and investigate the effects of the tachyon scalar field on the structure formation in flat FRW universe. We calculate $\\delta_{c}(z_{c})$, $\\lambda(z_{c})$, $\\xi(z_{c})$, $\\Delta_{V}(z_{c})$, $\\log [\
Symmetry breaking and restoration for interacting scalar and gauge fields in Lifshitz type theories
Farakos, K.; Metaxas, D.
2012-05-01
We consider the one-loop effective potential at zero and finite temperature in field theories with anisotropic space-time scaling, with critical exponent z = 2, including both scalar and gauge fields. Depending on the relative strength of the coupling constants for the gauge and scalar interactions, we find that there is a symmetry breaking term induced at one loop at zero temperature and we find symmetry restoration through a first-order phase transition at high temperature.
Symmetry breaking and restoration for interacting scalar and gauge fields in Lifshitz type theories
Farakos, K
2011-01-01
We consider the one-loop effective potential at zero and finite temperature in field theories with anisotropic space-time scaling, with critical exponent $z=2$, including both scalar and gauge fields. Depending on the relative strength of the coupling constants for the gauge and scalar interactions, we find that there is a symmetry breaking term induced at one-loop at zero temperature and we find symmetry restoration through a first-order phase transition at high temperature.
Symmetry breaking and restoration for interacting scalar and gauge fields in Lifshitz type theories
Energy Technology Data Exchange (ETDEWEB)
Farakos, K., E-mail: kfarakos@central.ntua.gr [Department of Physics, National Technical University of Athens, Zografou Campus, 15780 Athens (Greece); Metaxas, D., E-mail: metaxas@central.ntua.gr [Department of Physics, National Technical University of Athens, Zografou Campus, 15780 Athens (Greece)
2012-05-01
We consider the one-loop effective potential at zero and finite temperature in field theories with anisotropic space-time scaling, with critical exponent z=2, including both scalar and gauge fields. Depending on the relative strength of the coupling constants for the gauge and scalar interactions, we find that there is a symmetry breaking term induced at one loop at zero temperature and we find symmetry restoration through a first-order phase transition at high temperature.
Generalized second law of thermodynamics for non-canonical scalar field model with corrected-entropy
Das, Sudipta; Debnath, Ujjal; Mamon, Abdulla Al
2015-01-01
In this work, we have considered a non-canonical scalar field dark energy model in the framework of flat FRW background. It has also been assumed that the dark matter sector interacts with the non-canonical dark energy sector through some interaction term. Using the solutions for this interacting non-canonical scalar field dark energy model, we have investigated the validity of generalized second law (GSL) of thermodynamics in various scenarios using first law and area law of thermodynamics. ...
Note on the thermodynamics and the speed of sound of a scalar field
Piattella, Oliver F; Bilić, Neven
2014-01-01
We investigate the correspondence between a perfect fluid and a scalar field and show a possible way of expressing thermodynamic quantities such as entropy, particle number density, temperature and chemical potential in terms of the scalar field phi and its kinetic term X. We prove a theorem which relates isentropy with purely kinetic Lagrangian. As an application, we study the evolution of the gravitational potential in cosmological perturbation theory.
Quasistationary solutions of self-gravitating scalar fields around collapsing stars
Sanchis-Gual, Nicolas; Degollado, Juan Carlos; Montero, Pedro J.; Font, José A.; Mewes, Vassilios
2015-10-01
Recent work has shown that scalar fields around black holes can form long-lived, quasistationary configurations surviving for cosmological time scales. Scalar fields thus cannot be discarded as viable candidates for dark matter halo models in galaxies around central supermassive black holes (SMBHs). One hypothesized formation scenario of most SMBHs at high redshift is the gravitational collapse of supermassive stars (SMSs) with masses of ˜105 M⊙ . Any such scalar field configurations must survive the gravitational collapse of a SMS in order to be a viable model of physical reality. To check for the postcollapse survival of these configurations and to follow the dynamics of the black hole-scalar field system we present in this paper the results of a series of numerical relativity simulations of gravitationally collapsing, spherically symmetric stars surrounded by self-gravitating scalar fields. We use an ideal fluid equation of state with adiabatic index Γ =4 /3 which is adequate to simulate radiation-dominated isentropic SMSs. Our results confirm the existence of oscillating, long-lived, self-gravitating scalar field configurations around nonrotating black holes after the collapse of the stars.
Reconstructing the Universe Evolution from Loop Quantum Cosmology Scalar Fields
Oikonomou, V K
2016-01-01
We extend the scalar-tensor reconstruction techniques for classical cosmology frameworks, in the context of loop quantum cosmology. After presenting in some detail how the equations are generalized in the loop quantum cosmology case, we discuss which new features and limitations does the quantum framework brings along, and we use various illustrative examples in order to demonstrate how the method works. As we show the energy density has two different classes of solutions, and one of these yields the correct classical limit while the second captures the quantum phenomena. We study in detail the scalar tensor reconstruction method for both these solutions. Also we discuss some scenarios for which the Hubble rate becomes unbounded at finite time, which corresponds for example in a case that a Big Rip occurs. As we show this issue is non-trivial and we discuss how this case should be treated in a consistent way. Finally, we investigate how the classical stability conditions for the scalar-tensor solutions are ge...
Effective theory of a doubly charged singlet scalar: complementarity of neutrino physics and the LHC
King, Stephen F; Panizzi, Luca
2014-01-01
We consider a rather minimal extension of the Standard Model involving just one extra particle, namely a single $SU(2)_L$ singlet scalar $S^{++}$ and its antiparticle $S^{--}$. We propose a model independent effective operator, which yields an effective coupling of $S^{\\pm \\pm}$ to pairs of same sign weak gauge bosons, $W^{\\pm} W^{\\pm}$. We also allow tree-level couplings of $S^{\\pm \\pm}$ to pairs of same sign right-handed charged leptons $l^{\\pm}_Rl'^{\\pm}_R$ of the same or different flavour. We calculate explicitly the resulting two-loop diagrams in the effective theory responsible for neutrino mass and mixing. We propose sets of benchmark points for various $S^{\\pm \\pm}$ masses and couplings which can yield successful neutrino masses and mixing, consistent with limits on charged lepton flavour violation (LFV) and neutrinoless double beta decay. We discuss the prospects for $S^{\\pm \\pm}$ discovery at the LHC, for these benchmark points, including single and pair production and decay into same sign leptons p...
The Nambu-Goto string occupied by scalar fields: a two-loop calculation
International Nuclear Information System (INIS)
We study the properties of the Nambu-Goto string populated by a set of self-interacting scalar fields. The contributions to the static quark-antiquark potential coming from the string, fields and string-field interactions are obtained in a two-loop calculation. For an infinitely-long string or massless scalar fields, the interaction between string and fields disappears. Also we observe that the energy of the system increases and the deconfinement radius (the value of R for which the potential vanishes) decreases as the value of the coupling parameter grows. (author)
Role of a scalar field in the radiation dominated epoch of the Universe evolution
International Nuclear Information System (INIS)
Recently discovered accelerating expansion of the Universe is of current importance in the theoretical investigation of the Universe evolution. Presumably the reason of such a behavior is the presence of dark energy which by certain estimates constitutes 70 per cent of the Universe content and generates 'repulsive forces'. In the present work the construction of the cosmological model which takes into account the presence of dark energy is realized within the framework of Jordan-Brans-Dicke tensor-scalar theory with dominating non-minimally coupled scalar field in the presence of the cosmological scalar. The radiation dominated epoch is considered
Landau pole in the Standard Model with weakly interacting scalar fields
Hamada, Yuta; Kawana, Kiyoharu; Tsumura, Koji
2015-07-01
We consider the Standard Model with a new scalar field X which is an nX representation of the SU (2)L with a hypercharge YX. The renormalization group running effects on the new scalar quartic coupling constants are evaluated. Even if we set the scalar quartic coupling constants to be zero at the scale of the new scalar field, the coupling constants are induced by the one-loop effect of the weak gauge bosons. Once non-vanishing couplings are generated, the couplings rapidly increase by renormalization group effect of the quartic coupling constant itself. As a result, the Landau pole appears below Planck scale if nX ≥ 4. We find that the scale of the obtained Landau pole is much lower than that evaluated by solving the one-loop beta function of the gauge coupling constants.
Landau pole in the Standard Model with weakly interacting scalar fields
Hamada, Yuta; Tsumura, Koji
2015-01-01
We consider the Standard Model with a new scalar field $X$ which is a $n_X^{}$ representation of the $SU(2)_L$ with a hypercharge $Y_X$. The renormalization group running effects on the new scalar quartic coupling constants are evaluated. Even if we set the scalar quartic coupling constants to be zero at the scale of the new scalar field, the coupling constants are induced by the one-loop effect of the weak gauge bosons. Once non-vanishing couplings are generated, the couplings rapidly increase by renormalization group effect of the quartic coupling constant itself. As a result, the Landau pole appears below Planck scale if $n_X^{}\\geq 4$. We find that the scale of the obtained Landau pole is much lower than that evaluated by solving the one-loop beta function of the gauge coupling constants.
Rapidly rotating neutron stars with a massive scalar field - structure and universal relations
Doneva, Daniela D
2016-01-01
We construct rapidly rotating neutron star models in scalar-tensor theories with a massive scalar field. The fact that the scalar field has nonzero mass leads to very interesting results since the allowed range of values of the coupling parameters is significantly broadened. These deviations from pure general relativity can be very large for values of the parameters that are in agreement with the observations. The rapid rotation can magnify the differences several times compared to the static case. The universal relations between the normalized moment of inertia and quadrupole moment are also investigated both for the slowly and rapidly rotating cases. The results show that these relations are still EOS independent up to a large extend and the deviations from pure general relativity can be large. This places the massive scalar-tensor theories amongst the few alternative theories of gravity that can be tested via the universal $I$-Love-$Q$ relations.
The entropy of isolated horizons in non-minimally coupling scalar field theory from BF theory
Wang, Jingbo
2015-01-01
In this paper, the entropy of isolated horizons in non-minimally coupling scalar field theory and in the scalar-tensor theory of gravitation is calculated by counting the degree of freedom of quantum states in loop quantum gravity. Instead of boundary Chern-Simons theory, the boundary BF theory is used. The advantages of the new approaches are that no spherical symmetry is needed, and that the final result matches exactly with the Wald entropy formula.
Coexistence of black holes and a long-range scalar field in cosmology
Zloshchastiev, Konstantin G.
2004-01-01
The exactly solvable scalar hairy black hole model (originated from the modern high-energy theory) is proposed. It turns out that the existence of black holes (BH) is strongly correlated to global scalar field, in a sense that they mutually impose bounds upon their physical parameters like the BH mass (lower bound) or the cosmological constant (upper bound). We consider the same model also as a cosmological one and show that it agrees with recent experimental data; additionally, it provides a...
Inflationary universe in a conformally-invariant two scalar-field theory with an $R^2$ term
Bamba, Kazuharu
2016-01-01
We investigate the inflationary universe in a theory where two scalar fields non-minimally coupling to the scalar curvature and an extra $R^2$ term exist and the conformal invariance is broken. In particular, the slow-roll inflation is explored for the case that one scalar field is dynamical and that two scalar fields are dynamical. As a result, we show that the spectral index of the curvature perturbations and the tensor-to-scalar ratio of the density perturbations can be compatible with the Planck results. It is also demonstrated that the graceful exit from inflation can be realized.
Dark Energy as a Cosmological Consequence of Existence of the Dirac Scalar Field in Nature
Directory of Open Access Journals (Sweden)
O. V. Babourova
2015-01-01
Full Text Available The solution of the field equations of the conformal theory of gravitation with Dirac scalar field in Cartan-Weyl spacetime at the very early Universe is obtained. In this theory dark energy (described by an effective cosmological constant is a function of the Dirac scalar field β. This solution describes the exponential decreasing of β at the inflation stage and has a limit to a constant value of the dark energy at large time. This can give a way to solving the fundamental cosmological constant problem as a consequence of the fields dynamics in the early Universe.
Search for charged scalars in e+e- annihilation up to 64 GeV CM energy
International Nuclear Information System (INIS)
A search for the production of charged scalars has been carried out in e+e- annihilation at center of mass energies up to 64 GeV with 61.1 pb-1 of integrated luminosity using the VENUS detector at TRISTAN. The assumptions concerning the production and decay of hypothetical charged scalars are minimal; they are expected to be singly charged and decay into a pair of fermions. No positive evidence for their production has been found in a study of all combinations of the anti lν(lanti ν) and Uanti D(anti UD) decay channels. We have excluded the mass region of 8.0-20.0 GeV/c2 regardless of the decay mode. (orig.)
Search for charged scalars in e sup + e sup - annihilation up to 64 GeV CM energy
Energy Technology Data Exchange (ETDEWEB)
Yuzuki, T.; Haba, J.; Kanda, N.; Nagashima, Y.; Sugimoto, S.; Suzuki, A.; Takaki, H.; Takita, M. (Dept. of Physics, Osaka Univ., Toyonaka (Japan)); Abe, K. (Dept. of Physics, Tohoku Univ., Sendai (Japan)); Amako, K.; Arai, Y.; Fukawa, M.; Fukushima, Y.; Ishihara, N.; Kamitani, T.; Kanematsu, N.; Kanzaki, J.; Kondo, T.; Korhonen, T.T.; MacNaughton, J.; Matsui, T.; Odaka, S.; Ogawa, K.; Ohama, T.; Sakamoto, H.; Sakuda, M.; Shirai, J.; Sumiyoshi, T.; Takasaki, F.; Tsuboyama, T.; Uehara, S.; Unno, Y.; Watase, Y.; Yamada, Y. (KEK, National Lab. for High Energy Physics, Ibaraki (Japan)); Asano, Y.; Mori, S.; Shirakata, M.; Takada, Y.; Yonezawa, Y. (Inst. of Applied Physics, Univ. of Tsukuba, Ibaraki (Japan)); Chiba, M.; Fukui, T.; Hinode, F.; Hirose, T.; Minami, M.; Narita, Y.; Oyama, T.; Utsumi, M.; Watanabe, T.; Yabuki, F. (Dept. of Physics, Tokyo Metropolitan Univ. (Japan)); Chiba, Y.; Ohsugi, T.; Taketani, A.; Terunuma, N. (Dept. of Physics, Hiroshima Univ. (Japan)); Daigo, M. (Wak
1991-09-12
A search for the production of charged scalars has been carried out in e{sup +}e{sup -} annihilation at center of mass energies up to 64 GeV with 61.1 pb{sup -1} of integrated luminosity using the VENUS detector at TRISTAN. The assumptions concerning the production and decay of hypothetical charged scalars are minimal; they are expected to be singly charged and decay into a pair of fermions. No positive evidence for their production has been found in a study of all combinations of the anti l{nu}(lanti {nu}) and Uanti D(anti UD) decay channels. We have excluded the mass region of 8.0-20.0 GeV/c{sup 2} regardless of the decay mode. (orig.).
Inflation in a conformally invariant two-scalar-field theory with an extra R{sup 2} term
Energy Technology Data Exchange (ETDEWEB)
Bamba, Kazuharu, E-mail: bamba@sss.fukushima-u.ac.jp [Division of Human Support System, Faculty of Symbiotic Systems Science, Fukushima University, 960-1296, Fukushima (Japan); Leading Graduate School Promotion Center, Ochanomizu University, 112-8610, Tokyo (Japan); Department of Physics, Graduate School of Humanities and Sciences, Ochanomizu University, 112-8610, Tokyo (Japan); Odintsov, Sergei D. [Institut de Ciencies de lEspai (IEEC-CSIC), Campus UAB, Carrer de Can Magrans, s/n 08193 Cerdanyola del Valles, Barcelona (Spain); Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys 23, 08010, Barcelona (Spain); Tretyakov, Petr V. [Joined Institute for Nuclear Research, Dubna, Moscow Region (Russian Federation)
2015-07-23
We explore inflationary cosmology in a theory where there are two scalar fields which non-minimally couple to the Ricci scalar and an additional R{sup 2} term, which breaks the conformal invariance. Particularly, we investigate the slow-roll inflation in the case of one dynamical scalar field and that of two dynamical scalar fields. It is explicitly demonstrated that the spectral index of the scalar mode of the density perturbations and the tensor-to-scalar ratio can be consistent with the observations obtaind by the recent Planck satellite. The graceful exit from the inflationary stage is achieved as in convenient R{sup 2} gravity. We also propose the generalization of the model under discussion with three scalar fields.
Inflation in a conformally invariant two-scalar-field theory with an extra R{sup 2} term
Energy Technology Data Exchange (ETDEWEB)
Bamba, Kazuharu [Fukushima University, Division of Human Support System, Faculty of Symbiotic Systems Science, Fukushima (Japan); Ochanomizu University, Leading Graduate School Promotion Center, Tokyo (Japan); Ochanomizu University, Department of Physics, Graduate School of Humanities and Sciences, Tokyo (Japan); Odintsov, Sergei D. [Institut de Ciencies de l' Espai (IEEC-CSIC), Barcelona (Spain); Institucio Catalana de Recerca i Estudis Avancats (ICREA), Barcelona (Spain); Tretyakov, Petr V. [Joined Institute for Nuclear Research, Dubna (Russian Federation)
2015-07-15
We explore inflationary cosmology in a theory where there are two scalar fields which non-minimally couple to the Ricci scalar and an additional R{sup 2} term, which breaks the conformal invariance. Particularly, we investigate the slow-roll inflation in the case of one dynamical scalar field and that of two dynamical scalar fields. It is explicitly demonstrated that the spectral index of the scalar mode of the density perturbations and the tensor-to-scalar ratio can be consistent with the observations obtained by the recent Planck satellite. The graceful exit from the inflationary stage is achieved as in convenient R{sup 2} gravity. We also propose the generalization of the model under discussion with three scalar fields. (orig.)
International Nuclear Information System (INIS)
In this work it is proposed a transformation which is useful in order to simplify non-polynomial potentials given in the form of an exponential. As an application, it is shown that the quantum Liouville field theory may be mapped into a field theory with a polynomial interaction between two scalar fields and a massive vector field
Is Sextans dwarf galaxy in a scalar field dark matter halo?
Lora, V
2014-01-01
The Bose-Einstein condensate/scalar field dark matter model, considers that the dark matter is composed by spinless-ultra-light particles which can be described by a scalar field. This model is an alternative model to the $\\Lambda$-cold dark matter paradigm, and therefore should be studied at galactic and cosmological scales. Dwarf spheroidal galaxies have been very useful when studying any dark matter theory, because the dark matter dominates their dynamics. In this paper we study the Sextans dwarf spheroidal galaxy, embedded in a scalar field dark matter halo. We explore how the dissolution time-scale of the stellar substructures in Sextans, constrain the mass, and the self-interacting parameter of the scalar field dark matter boson. We find that for masses in the range $(0.12< m_{\\phi}<8) \\times10^{-22}$~eV, scalar field dark halos without self-interaction would have cores large enough to explain the longevity of the stellar substructures in Sextans, and small enough mass to be compatible with dynami...
Decoherence and disentanglement of qubits detecting scalar fields in an expanded universe
Li, Yujie; Shi, Yu
2016-01-01
We consider Unruh-Wald qubit detector model adopted for the far future region of an exactly solvable 1+1 dimensional scalar field theory in a Robertson-Walker expanding spacetime. It is shown that the expansion of the universe in its history enhances the decoherence of the qubit coupled with a scalar field. Moreover, we consider two entangled qubits, each locally coupled a scalar field. The expansion of the universe in its history degrades the entanglement between the qubits, and can lead to entanglement sudden death if the initial entanglement is small enough. The details depend on the parameters characterizing the expansion of the universe. This work, albeit on a toy model, suggests that the history of the universe might be probed through the coherent and entanglement behavior of future detectors of quantum fields.
Are black holes a serious threat to scalar field dark matter models?
Barranco, Juan; Degollado, Juan Carlos; Diez-Tejedor, Alberto; Megevand, Miguel; Alcubierre, Miguel; Núñez, Darío; Sarbach, Olivier
2011-01-01
Classical scalar fields have been proposed as possible candidates for the dark matter component of the universe. Given the fact that super-massive black holes seem to exist at the center of most galaxies, in order to be a viable candidate for the dark matter halo a scalar field configuration should be stable in the presence of a central black hole, or at least be able to survive for cosmological time-scales. In the present work we consider a scalar field as a test field on a Schwarzschild background, and study under which conditions one can obtain long-lived configurations. We present a detailed study of the Klein-Gordon equation in the Schwarzschild spacetime, both from an analytical and numerical point of view, and show that indeed there exist quasi-stationary solutions that can remain surrounding a black hole for large time-scales.
Fate of oscillating scalar fields in the thermal bath and their cosmological implications
Yokoyama, J
2004-01-01
Relaxation process of a coherent scalar field oscillation in the thermal bath is investigated using nonequilibrium quantum field theory. The Langevin-type equation of motion is obtained which has a memory term and both additive and multiplicative noise terms. The dissipation rate of the oscillating scalar field is calculated for various interactions such as Yukawa coupling, three-body scalar interaction, and biquadratic interaction. When the background temperature is larger than the oscillation frequency, the dissipation rate arising from the interactions with fermions is suppressed due to the Pauli blocking, while it is enhanced for interactions with bosons due to the induced effect. In both cases, we find that the microphysical detailed balance relation drives the oscillating field to a thermal equilibrium state. That is, for low-momentum modes, the classical fluctuation-dissipation theorem holds and they relax to a state the equipartition law is satisfied, while higher-momentum modes reach the state the nu...
Are black holes a serious threat to scalar field dark matter models?
International Nuclear Information System (INIS)
Classical scalar fields have been proposed as possible candidates for the dark matter component of the universe. Given the fact that supermassive black holes seem to exist at the center of most galaxies, in order to be a viable candidate for the dark matter halo a scalar field configuration should be stable in the presence of a central black hole, or at least be able to survive for cosmological time scales. In the present work we consider a scalar field as a test field on a Schwarzschild background, and study under which conditions one can obtain long-lived configurations. We present a detailed study of the Klein-Gordon equation in the Schwarzschild space-time, both from an analytical and numerical point of view, and show that indeed there exist quasistationary solutions that can remain surrounding a black hole for large time scales.
Is the DBI scalar field as fragile as other k -essence fields?
Mukohyama, Shinji; Namba, Ryo; Watanabe, Yota
2016-07-01
Caustic singularity formations in shift-symmetric k -essence and Horndeski theories on a fixed Minkowski spacetime were recently argued. In n dimensions, this singularity is the (n -2 )-dimensional plane in spacetime at which second derivatives of a field diverge and the field loses single-valued description for its evolution. This does not necessarily imply a pathological behavior of the system but rather invalidates the effective description. The effective theory would thus have to be replaced by another to describe the evolution thereafter. In this paper, adopting the planar-symmetric 1 +1 -dimensional approach employed in the original analysis, we seek all k -essence theories in which generic simple wave solutions are free from such caustic singularities. Contrary to the previous claim, we find that not only the standard canonical scalar but also the DBI scalar are free from caustics, as far as planar-symmetric simple wave solutions are concerned. Addition of shift-symmetric Horndeski terms does not change the conclusion.
Scalar field reconstruction of power-law entropy-corrected holographic dark energy
Ebrahimi, Esmaeil
2010-01-01
A so called "power-law entropy-corrected holographic dark energy" (PLECHDE) was recently proposed to explain the dark energy dominated universe. This model is based on the power-law corrections to black hole entropy which appear in dealing with the entanglement of quantum fields between inside and outside of the horizon. In this paper, we suggest a correspondence between interacting PLECHDE and tachyon, quintessence, K-essence and dilaton scalar field models of dark energy in a non-flat FRW universe. Then, we reconstruct the potential terms accordingly, and present the dynamical equations which describe the evolution of the scalar field dark energy models.
The innocuousness of adiabatic instabilities in coupled scalar field-dark matter models
Corasaniti, Pier Stefano
2010-01-01
Non-minimally coupled scalar field models suffer of unstable growing modes at the linear perturbation level. The nature of these instabilities depends on the dynamical state of the scalar field. In particular in systems which admit adiabatic solutions, large scale instabilities are suppressed by the slow-roll dynamics of the field. Here we review these results and present a preliminary likelihood data analysis suggesting that along adiabatic solutions coupled models with coupling of order of gravitational strength can provide viable cosmological scenarios satisfying constraints from SN Ia, CMB and large scale structure data.
Anisotropic scalar field emission from TeV scale black hole
Ida, D; Park, S C; Ida, Daisuke; Oda, Kin-ya; Park, Seong Chan
2005-01-01
Black holes are predicted to be copiously produced at the CERN Large Hadron Collider in the scenarios of TeV scale gravity. We report recent progress in studying decay of such a higher dimensional black hole in D=4+n dimensions through the Hawking radiation into brane localized fields taking into account its angular momentum which is indispensable for realistic simulations. Presented is the greybody factors for a scalar field emission, which confirms our previous results in low energy approximation: (i) the existence of super-radiance modes and (ii) the non-trivial angular distribution of radiated scalar field. Phenomenological implications and future plans are discussed.
Sterile neutrino dark matter and low scale leptogenesis from a charged scalar
Energy Technology Data Exchange (ETDEWEB)
Frigerio, Michele [Laboratoire Charles Coulomb, Montpellier (France); Yaguna, Carlos E. [Universitaet Muenster, Institut fuer Theoretische Physik, Muenster (Germany)
2015-01-01
We show that novel paths to dark matter generation and baryogenesis are open when the standard model is extended with three sterile neutrinos N{sub i} and a charged scalar δ{sup +}. Specifically,we propose a new production mechanism for the dark matter particle - multi-keV sterile neutrino, N{sub 1} - that does not depend on the active-sterile mixing angle and does not rely on a large primordial lepton asymmetry. Instead, N{sub 1} is produced, via freeze-in, by the decays of δ{sup +} while it is in equilibrium in the early Universe. In addition, we demonstrate that, thanks to the couplings between the heavier sterile neutrinos N{sub 2,3} and δ{sup +}, baryogenesis via leptogenesis can be realized close to the electroweak scale. The lepton asymmetry is generated either by N{sub 2,3}-decays for masses M{sub 2,3} >or similar TeV, or by N{sub 2,3}-oscillations for M{sub 2,3} ∝ GeV. Experimental signatures of this scenario include an X-ray line from dark matter decays, and the direct production of δ{sup +} at the LHC. This model thus describes a minimal, testable scenario for neutrino masses, the baryon asymmetry, and dark matter. (orig.)
Stability analysis of 5D gravitational solutions with N bulk scalar fields
Gherghetta, Tony
2011-01-01
We study the stability of 5D gravitational solutions containing an arbitrary number of scalar fields. A closed set of equations is derived which governs the background and perturbations of N scalar fields and the metric, for arbitrary bulk and boundary scalar potentials. In particular the effect of the energy-momentum tensor of the scalar fields on the geometry is fully taken into account, together with all the perturbations of the system. The equations are explicitly written as an eigenvalue problem, which can be readily solved to determine the stability of the system and obtain the properties of the fluctuations, such as masses and couplings. As an example, we study a dynamical soft-wall model with two bulk scalar fields used to model the hadron spectrum of QCD and the Higgs sector of electroweak physics. It is shown that there are no tachyonic modes, and that there is a (radion) mode whose mass is suppressed by a large logarithm compared to that of the other Kaluza-Klein modes.
Bakon, Bartlomiej; Rogatko, Marek
2013-01-01
We proved that strictly stationary Einstein-Maxwell-axion-dilaton spacetime with negative cosmological constant could not support a nontrivial configuration of complex scalar fields. We considered the general case of the arbitrary number of U(1) gauge fields in the theory under consideration.
Chang, We-Fu; Wong, Chi-Fong; Xu, Fanrong
2016-01-01
We considered a neutrino mass generating model which employs a scalar leptoquark, $\\Delta$, and a scalar diquark, $S$. The new scalars $\\Delta$ and $S$ carry the standard model $SU(3)_c\\times SU(2)_L\\times U(1)_Y$ quantum numbers $(3,1,-1/3)$ and $(6,1,-2/3)$ respectively. The neutrino masses are generated at the two-loop level similar to that in the Zee-Babu model\\cite{Zee-Babu}. And $\\Delta/S$ plays the role of the doubly/singly charged scalar in the Zee-Babu model. With a moderate working assumption that the magnitudes of the six Yukawa couplings between $S$ and the down-type quarks are of the same order, strong connections were found between the neutrino masses and the charged lepton flavor violating(cLFV) processes. In particular, $Z\\rightarrow \\overline{l} l'$, and $l\\rightarrow l' \\gamma$ were studied and it was found that some portions of the parameter space of this model are within the reach of the planned cLFV experiments. Interesting lower bounds on the cLFV processes were predicted that $B(Z\\right...
Light-like κ-deformations and scalar field theory via Drinfeld twist
Jurić, Tajron; Meljanac, Stjepan; Samsarov, Andjelo
2015-08-01
In this article we will use the Drinfeld twist leading to light-like κ-deformations of Poincaré algebra. We shall apply the standard Hopf algebra methods in order to define the star-product, which shall be used to formulate a scalar field theory compatible with κ-Poincaré-Hopf algebra. Using this approach we show that there is no problem with formulating integration on κ-Minkowski space and no need for introducing a new measure. We have shown that the ★-product obtained from this twist enables us to define a free scalar field theory on κ-Minkowski space that is equivalent to a commutative one on a usual Minkowski space. We also discuss the interacting ϕ4 scalar field model compatible with κ-Poincaré-Hopf algebra.
Entanglement Entropy Renormalization for the NC scalar field coupled to classical BTZ geometry
Jurić, Tajron
2016-01-01
In this work, we consider a noncommutative (NC) massless scalar field coupled to the classical nonrotational BTZ geometry. In a manner of the theories where the gravity emerges from the underlying scalar field theory, we study the effective action and the entropy derived from this noncommutative model. In particular, the entropy is calculated by making use of the two different approaches, the brick wall method and the heat kernel method designed for spaces with conical singularity. We show that the UV divergent structures of the entropy, obtained through these two different methods, agree with each other. It is also shown that the same renormalization condition that removes the infinities from the effective action can also be used to renormalize the entanglement entropy for the same system. Besides, the interesting feature of the NC model considered here is that it allows an interpretation in terms of an equivalent system comprising of a commutative massive scalar field, but in a modified geometry; that of th...
Shaw, D J; Barrow, John D.; Shaw, Douglas J.
2006-01-01
We apply the method of matched asymptotic expansions to analyse whether cosmological variations in physical `constants' and scalar fields are detectable, locally, on the surface of local gravitationally bound systems such as planets and stars, or inside virialised systems like galaxies and clusters. We assume spherical symmetry and derive a sufficient condition for the local time variation of the scalar fields that drive varying constants to track the cosmological one. We calculate under number of specific examples in detail by matching the Schwarzschild spacetime to spherically symmetric inhomogeneous Tolman-Bondi metrics in an intermediate region by rigorously construction matched asymptotic expansions on cosmological and local astronomical scales which overlap in an intermediate domain. We conclude that, independent of the details of the scalar-field theory describing the varying 'constant', the condition for cosmological variations to be measured locally is almost always satisfied in physically realistic ...
Closed star product on noncommutative $\\mathbb{R}^3$ and scalar field dynamics
Jurić, Tajron; Wallet, Jean-Christophe
2016-01-01
We consider the noncommutative space $\\mathbb{R}^3_\\theta$, a deformation of $\\mathbb{R}^3$ for which the star product is closed for the trace functional. We study one-loop IR and UV properties of the 2-point function for real and complex noncommutative scalar field theories with quartic interactions and Laplacian on $\\mathbb{R}^3$ as kinetic operator. We find that the 2-point functions for these noncommutative scalar field theories have no IR singularities in the external momenta, indicating the absence of UV/IR mixing. We also find that the 2-point functions are UV finite with the deformation parameter $\\theta$ playing the role of a natural UV cut-off. The possible origin of the absence of UV/IR mixing in noncommutative scalar field theories on $\\mathbb{R}^3_\\theta$ as well as on $\\mathbb{R}^3_\\lambda $, another deformation of $\\mathbb{R}^3$, is discussed.
Holographic dark energy in Brans-Dicke cosmology with chameleon scalar field
Energy Technology Data Exchange (ETDEWEB)
Setare, M.R., E-mail: rezakord@ipm.i [Department of Science of Bijar, University of Kurdistan, Bijar (Iran, Islamic Republic of); Jamil, Mubasher, E-mail: mjamil@camp.edu.p [Center for Advanced Mathematics and Physics, National University of Sciences and Technology, Rawalpindi 46000 (Pakistan)
2010-06-07
We study a cosmological implication of holographic dark energy in the Brans-Dicke gravity. We employ the holographic model of dark energy to obtain the equation of state for the holographic energy density in non-flat (closed) universe enclosed by the event horizon measured from the sphere of horizon named L. Our analysis shows that one can obtain the phantom crossing scenario if the model parameter {alpha} (of order unity) is tuned accordingly. Moreover, this behavior is achieved by treating the Brans-Dicke scalar field as a Chameleon scalar field and taking a non-minimal coupling of the scalar field with matter. Hence one can generate phantom-like equation of state from a holographic dark energy model in non-flat universe in the Brans-Dicke cosmology framework.
Does a scalar meson field represent an irrotational perfect fluid in bimetric theory?
International Nuclear Information System (INIS)
The problems of homogeneous plane symmetric perfect fluid and massive scalar field are investigated in Rosen's bimetric theory. It is shown that a macro cosmological model represented by perfect fluid distribution does not exist and only a vacuum model can be constructed whereas in case of a micro cosmological model represented by a scalar meson field exist and the model is obtained. Moreover it is shown that the massive scalar field cannot be equivalent to irrotational perfect fluid neither through the identification of the the corresponding eigenvalues of their energy momentum tensors nor through the transformation as in the case of Tiwary et all and Tabensky and Taub respectively in general theory of relativity. (authors)
Revisiting the spectrum of a scalar field in an anisotropic universe
Kim, Hyeong-Chan
2012-01-01
We revisit the issue on signatures of pre-inflationary background anisotropy by considering the quantization of a massless and minimally coupled scalar field in an axially symmetric Kasner background, mimicking cosmological perturbations. We show that the power spectrum of the scalar field fluctuation has a negligible difference from the standard inflation in the non-planar directions, but it has a sharp peak around the symmetry plane. For the non-planar high-momentum modes, we use the WKB approximation for the first period and the asymptotic approximation based on the de Sitter solution for the next period. At the boundary, two mode functions have the same accuracy with error of $O({H_{i}}/k)$. We calculate the approximation up to the order of $({H_{i}}/k)^6$ and show that the power spectrum of the scalar field fails to get corrections until we execute the approximation up to $6^{\\rm th}$ order.
Bulk scalar field in brane-worlds with induced gravity inspired by the L(R) term
Energy Technology Data Exchange (ETDEWEB)
Heydari-Fard, M. [Department of Physics, The University of Qom, Qom 37185-359 (Iran, Islamic Republic of); Sepangi, H.R., E-mail: heydarifard@qom.ac.ir, E-mail: hr-sepangi@sbu.ac.ir [Department of Physics, Shahid Beheshti University, Evin, Tehran 19839 (Iran, Islamic Republic of)
2009-01-15
We obtain the effective field equations in a brane-world scenario within the framework of a DGP model where the action on the brane is an arbitrary function of the Ricci scalar, L(R), and the bulk action includes a scalar field in the matter Lagrangian. We obtain the Friedmann equations and acceleration conditions in the presence of the bulk scalar field for the R{sup n} term in four-dimensional gravity.
Is Sextans dwarf galaxy in a scalar field dark matter halo?
Energy Technology Data Exchange (ETDEWEB)
Lora, V. [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, 69120 Heidelberg (Germany); Magaña, Juan, E-mail: vlora@ari.uni-heidelberg.de, E-mail: juan.magana@uv.cl [Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Avda. Gran Bretaña 1111, Valparaíso (Chile)
2014-09-01
The Bose-Einstein condensate/scalar field dark matter model, considers that the dark matter is composed by spinless-ultra-light particles which can be described by a scalar field. This model is an alternative model to the Λ-cold dark matter paradigm, and therefore should be studied at galactic and cosmological scales. Dwarf spheroidal galaxies have been very useful when studying any dark matter theory, because the dark matter dominates their dynamics. In this paper we study the Sextans dwarf spheroidal galaxy, embedded in a scalar field dark matter halo. We explore how the dissolution time-scale of the stellar substructures in Sextans, constrain the mass, and the self-interacting parameter of the scalar field dark matter boson. We find that for masses in the range (0.12< m{sub φ}<8) ×10{sup -22} eV, scalar field dark halos without self-interaction would have cores large enough to explain the longevity of the stellar substructures in Sextans, and small enough mass to be compatible with dynamical limits. If the self-interacting parameter is distinct to zero, then the mass of the boson could be as high as m{sub φ}≈2×10{sup -21} eV, but it would correspond to an unrealistic low mass for the Sextans dark matter halo . Therefore, the Sextans dwarf galaxy could be embedded in a scalar field/BEC dark matter halo with a preferred self-interacting parameter equal to zero.
Is Sextans dwarf galaxy in a scalar field dark matter halo?
International Nuclear Information System (INIS)
The Bose-Einstein condensate/scalar field dark matter model, considers that the dark matter is composed by spinless-ultra-light particles which can be described by a scalar field. This model is an alternative model to the Λ-cold dark matter paradigm, and therefore should be studied at galactic and cosmological scales. Dwarf spheroidal galaxies have been very useful when studying any dark matter theory, because the dark matter dominates their dynamics. In this paper we study the Sextans dwarf spheroidal galaxy, embedded in a scalar field dark matter halo. We explore how the dissolution time-scale of the stellar substructures in Sextans, constrain the mass, and the self-interacting parameter of the scalar field dark matter boson. We find that for masses in the range (0.12< mφ<8) ×10-22 eV, scalar field dark halos without self-interaction would have cores large enough to explain the longevity of the stellar substructures in Sextans, and small enough mass to be compatible with dynamical limits. If the self-interacting parameter is distinct to zero, then the mass of the boson could be as high as mφ≈2×10-21 eV, but it would correspond to an unrealistic low mass for the Sextans dark matter halo . Therefore, the Sextans dwarf galaxy could be embedded in a scalar field/BEC dark matter halo with a preferred self-interacting parameter equal to zero
Interacting Entropy-Corrected Holographic Scalar Field Models in Non-Flat Universe
International Nuclear Information System (INIS)
In this work we establish a correspondence between the tachyon, k-essence and dilaton scalar field models with the interacting entropy-corrected holographic dark (ECHD) model in non-flat FRW universe. The reconstruction of potentials and dynamics of these scalar fields according to the evolutionary behavior of the interacting ECHDE model are done. It has been shown that the phantom divide can not be crossed in ECHDE tachyon model while it is achieved for ECHDE k-essence and ECHDE dilaton scenarios. At last we calculate the limiting case of interacting ECHDE model, without entropy-correction. (geophysics, astronomy, and astrophysics)
Scalar field localization on 3-branes placed at a warped resolved conifold
Silva, J. E. G.; Almeida, C. A. S.
2011-01-01
We have studied the localization of scalar field on a 3-brane embedded in a six dimensional warped bulk of the form $M_{4}\\times C_{2}$, where $M_{4}$ is a 3-brane and $C_{2}$ is a 2-cycle of a six resolved conifold $\\mathcal{C}_{6}$ over a $T^{1,1}$ space. Since the resolved conifold is singularity-free in $r=0$ depending on a resolution parameter $a$, we have analyzed the behavior of the localization of scalar field when we vary the resolution parameter. On one hand, this enable us to study...
Pozdeeva, Ekaterina O; Toporensky, Alexey V; Vernov, Sergey Yu
2016-01-01
We explore dynamics of cosmological models with bounce solutions evolving on a spatially flat Friedmann-Lemaitre-Robertson-Walker background. We consider cosmological models that contain the Hilbert-Einstein curvature term, the induced gravity term with a negative coupled constant, and even polynomial potentials of the scalar field. Bounce solutions with non-monotonic Hubble parameters have been obtained and analyzed. The case when the scalar field has the conformal coupling and the Higgs potential with an opposite sign is studied in detail. In this model the evolution of the Hubble parameter of the bounce solution essentially depends on the sign of the cosmological constant.
Confinement and stability in presence of scalar fields and perturbation in the bulk
Bhattacharya, Pinaki
2014-01-01
In this paper we have considered a five-dimensional warped product spacetime with spacelike extra dimension and with a scalar field source in the bulk. We have studied the dynamics of the scalar field under different types of potential in an effort to explain the confinement of particles in the five-dimensional spacetime. The behaviour of the system is determined from the nature of damping force on the system. We have also examined the nature of the effective potential under different circumstances. Lastly we have studied the system to determine whether or not the system attains asymptotically stable condition for both unperturbed and perturbed condition.
On a generality degree of inflationary solutions in cosmological models with a scalar field
International Nuclear Information System (INIS)
The extent to which inflation stages are encountered in homogeneous cosmological models with a scalar field is investigated. Estimates of the ratio of noninflationary solutions to the total number of solutions in open and closed Friedman models and also in the homogeneous model of type I are obtained. For the type I model and open Friedman model the ratio is m/mp (i.e. the same as in the plane Friedman model; mp - Planck mass; m - mass related to the scalar field); for the closed Friedman model it is 1/4. Some considerations are presented for choosing the measure in the solution space of the models considered
Cosmological dynamics of scalar fields with kinetic corrections: Beyond the exponential potential
Dutta, Jibitesh; Tamanini, Nicola
2016-01-01
We expand the dynamical systems investigation of cosmological scalar fields characterised by kinetic corrections presented in [N. Tamanini, Phys. Rev. D 89 (2014) 083521]. In particular we do not restrict the analysis to exponential potentials only, but we consider arbitrary scalar field potentials and derive general results regarding the corresponding cosmological dynamics. Two specific potentials are then used as examples to show how these models can be employed not only to describe dark energy, but also to achieve dynamical crossing of the phantom barrier at late times. Stability and viability issues at the classical level are also discussed.
Suroso, Agus
2014-01-01
We discussed a mechanism that allows the universe to start from lower dimension ($d < 4$) in its very early era and evolves to four dimension at the end of the process. The mechanism is generated by a nonminimal derivative coupling of scalar field, where derivative terms of the scalar field coupled to curvature tensor. We solve the Einstein equations for a limit of large and nearly constant Hubble parameter and analyze the evolution of the Hubble parameter in this limit. The lower-dimensionality in early universe has advantages in the context of unification theory.
Scaling behaviour of a scalar field model of dark matter halos
Fuchs, B
2004-01-01
Galactic dark matter is modelled by a scalar field. In particular, it is shown that an analytically solvable toy model with a non-linear self-interaction potential U(Phi) leads to dark halo models which have the form of quasi-isothermal spheres. We argue that these fit better the observed rotation curves of galaxies than the centrally cusped halos of standard cold dark matter. The scalar field model predicts a proportionality between the central densities of the dark halos and the inverse of their core radii. We test this prediction successfully against a set of rotation curves of low surface brightness galaxies and nearby bright galaxies.
New holographic scalar field models of dark energy in non-flat universe
Energy Technology Data Exchange (ETDEWEB)
Karami, K., E-mail: KKarami@uok.ac.i [Department of Physics, University of Kurdistan, Pasdaran St., Sanandaj (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha (Iran, Islamic Republic of); Fehri, J. [Department of Physics, University of Kurdistan, Pasdaran St., Sanandaj (Iran, Islamic Republic of)
2010-02-08
Motivated by the work of Granda and Oliveros [L.N. Granda, A. Oliveros, Phys. Lett. B 671 (2009) 199], we generalize their work to the non-flat case. We study the correspondence between the quintessence, tachyon, K-essence and dilaton scalar field models with the new holographic dark energy model in the non-flat FRW universe. We reconstruct the potentials and the dynamics for these scalar field models, which describe accelerated expansion of the universe. In the limiting case of a flat universe, i.e. k=0, all results given in [L.N. Granda, A. Oliveros, Phys. Lett. B 671 (2009) 199] are obtained.
Induced inflation from a 5D purely kinetic scalar field formalism on warped product spaces
International Nuclear Information System (INIS)
Considering a separable and purely kinetic 5D scalar field we investigate the induction of 4D scalar potentials on a 4D constant foliation on the class of 5D warped product space-times. We obtain a quantum confinement of the inflaton modes given naturally from the model for at least a class of warping factors. We can recover a 4D inflationary scenario where the inflationary potential is geometrically induced from 5D and the effective equation of state in 4D that includes the effect of the inflaton field and the induced matter is Peff≅-ρeff. (orig.)
The M-sigma Relation of Super Massive Black Holes from the Scalar Field Dark Matter
Lee, Jae-weon; Lee, Jungjai; Kim, Hyeong-Chan
2015-01-01
We explain the M-sigma relation between the mass of super massive black holes in galaxies and the velocity dispersions of their bulges in the scalar field or the Bose-Einstein condensate dark matter model. The gravity of the central black holes changes boundary conditions of the scalar field at the galactic centers. Owing to the wave nature of the dark matter this significantly changes the galactic halo profiles even though the black holes are much lighter than the bulges. As a result the hea...
Space charge fields in DC cables
DEFF Research Database (Denmark)
McAllister, Iain Wilson; Crichton, George C; Pedersen, Aage
The space charge that accumulates in DC cables can, mathematically, be resolved into two components. One is related to the temperature and the other to the magnitude of the electric field strength. Analytical expressions for the electric fields arising from each of these space charge components are...... derived. Thereafter, the significance of these field components under both normal operating conditions and immediately following polarity reversal is discussed...
Sakalli, I.
2016-01-01
Hawking radiation of charged massive spin-0 particles are studied in the gravitational, electromagnetic, dilaton, and axion fields of rotating linear dilaton black holes. In this geometry, we separate the covariant Klein--Gordon equation into radial and angular parts and obtain the exact solutions of both the equations in terms of the confluent Heun functions. Using the radial solution, we analyze the behavior of the wave solutions near the event horizon of the rotating linear dilaton black h...
Propagator of a scalar field on a stationary slowly varying gravitational background
Kazinski, P O
2012-01-01
The propagator of a scalar field on a stationary slowly varying in space gravitational background is derived retaining only the second derivatives of the metric. The corresponding one-loop effective action is constructed. The propagator and the effective action turn out to depend nontrivially on the Killing vector defining the vacuum state and the Hamiltonian of a scalar field. The Hawking particle production is described in the quasiclassical approximation and the quasiclassical formula for the Hawking temperature is derived. The behaviour of the Unruh detector on a curved background is considered and the quasiclassical formula for the Unruh acceleration determining the Unruh temperature is derived. The radiation reaction problem on a curved background is discussed in view of the new approximate expression for the propagator. The correction to the mass squared of a scalar particle on a stationary gravitational background is obtained. This correction is analogous to the quantum correction to the particle mass...
A scalar field governed cosmological model from noncompact Kaluza-Klein theory
Aguilar, J E M; Saenz, F A; Aguilar, Jose Edgar Madriz; Bellini, Mauricio; Saenz, Francisco Astorga
2004-01-01
This paper is a review of a recently introduced cosmological model from a noncompact Kaluza-Klein theory for a single scalar field minimally coupled to gravity. We obtain that the 4D scalar potential has a geometrical origin and assume different representations in different frames. It should be responsible for the expansion of the universe. In this framework we explain the (neutral scalar field governed) evolution of the universe from an initially inflationary expansion that has a change of phase towards a decelerated expansion and thereinafter evolves towards the present day observed accelerated (quintessential) expansion. Finally, using the Hamilton-Jacobi formalism, we study extra force and extra mass from this 5D cosmological model.
Propagators for a quantized scalar field in a static closed universe
International Nuclear Information System (INIS)
In a previous paper, a massive scalar field in an expanding closed universe was canonically quantized by taking full account of its coupling-type with the background universe and of the latter's topological (spherical or elliptic) nature. General formulae (including the parts of vacuum fluctuation which should after all be removed by a suitable regularization) for the energy density and pressure of the quantized medium were derived. Various propagators for the quantized scalar field were also dealt with, because the Feynman propagator in particular became important as soon as the pair-creation of those particles was called for. However, there will be an intimate relation between the former hydrodynamic quantities and the pair-creation of their constituents. Accordingly, this problem is studied in detail by adopting a static closed universe (for simplicity in the reduction of various expressions derived in the previous paper) and examining the behavior of various bi-scalar propagators in the universe. (author)
A Lagrangian model for the evolution of turbulent magnetic and passive scalar fields
Hater, T; Grauer, R
2010-01-01
In this paper we present an extension of the \\emph{Recent Fluid Deformation (RFD)} closure introduced by Chevillard and Meneveau (2006) which was developed for modeling the time evolution of Lagrangian fluctuations in incompressible Navier-Stokes turbulence. We apply the RFD closure to study the evolution of magnetic and passive scalar fluctuations. This comparison is especially interesting since the stretching term for the magnetic field and for the gradient of the passive scalar are similar but differ by a sign such that the effect of stretching and compression by the turbulent velocity field is reversed. Probability density functions (PDFs) of magnetic fluctuations and fluctuations of the gradient of the passive scalar obtained from the RFD closure are compared against PDFs obtained from direct numerical simulations.
A general construction of conformal field theories from scalar anti-de Sitter quantum field theories
International Nuclear Information System (INIS)
We provide a new general setting for scalar interacting fields on the covering of a ( d+1 )-dimensional AdS spacetime. The formalism is used at first to construct a one-parameter family of field theories, each living on a corresponding spacetime submanifold of AdS, which is a cylinder RxSd-1 . We then introduce a limiting procedure which directly produces Luescher-Mack CFT's on the covering of the AdS asymptotic cone. Our generalized AdS → CFT construction is nonperturbative, and is illustrated by a complete treatment of two-point functions, the case of Klein-Gordon fields appearing as particularly simple in our context. We also show how the Minkowskian representation of these boundary CFT's can be directly generated by an alternative limiting procedure involving Minkowskian theories in horocyclic sections (nowadays called (d-1)-branes, 3-branes for AdS5 ). These theories are restrictions to the brane of the ambient AdS field theory considered. This provides a more general correspondence between the AdS field theory and a Poincare invariant QFT on the brane, satisfying all the Wightman axioms. The case of two-point functions is again studied in detail from this viewpoint as well as the CFT limit on the boundary
Radiation Like Scalar Field and Gauge Fields in Cosmology for a theory with Dynamical Time
Benisty, David
2016-01-01
Cosmological solutions with a scalar field behaving as radiation are obtained, in the context of gravitational theory with dynamical time. The solution requires the spacial curvature of the universe k, to be zero, unlike the standard radiation solutions, which do not impose any constraint on the spacial curvature of the universe. This is because only such $ k=0 $ radiation solutions poses a homothetic Killimg vector. This kind of theory can be used to generalize electromagnetism and other gauge theories, in curved space time, and there are no deviations from standard gauge filed equation (like Maxwell equations) in the case there exist a conformal Killing vector. But there could be departures from Maxwell and Yang Mills equations, for more general space times.
Spacetime Curvature in terms of Scalar Field Propagators
Saravani, Mehdi; Kempf, Achim
2015-01-01
We show how quantum fields can be used to measure the curvature of spacetime. In particular, we find that knowledge of the imprint that spacetime curvature leaves in the correlators of quantum fields suffices, in principle, to reconstruct the metric. We then consider the possibility that the quantum fields obey a natural ultraviolet cutoff, for example, at the Planck scale. We investigate how such a cutoff limits the spatial resolution with which curvature can be deduced from the properties of quantum fields. We find that the metric deduced from the quantum correlator exhibits a peculiar scaling behavior as the scale of the natural UV cutoff is approached.
Erices, Cristián; Martínez, Cristián
2015-08-01
The general stationary cylindrically symmetric solution of Einstein-massless scalar field system with a nonpositive cosmological constant is presented. It is shown that the general solution is characterized by four integration constants. Two of these essential parameters have a local meaning and characterize the gravitational field strength. The other two have a topological origin, as they define an improper coordinate transformation that provides the stationary solution from the static one. The Petrov scheme is considered to explore the effects of the scalar field on the algebraic classification of the solutions. In general, these spacetimes are of type I. However, the presence of the scalar field allows us to find a nonvacuum type O solution and a wider family of type D spacetimes, in comparison with the vacuum case. The mass and angular momentum of the solution are computed using the Regge-Teitelboim method in the case of a negative cosmological constant. In absence of a cosmological constant, the curvature singularities in the vacuum solutions can be removed by including a phantom scalar field, yielding nontrivial locally homogeneous spacetimes. These spacetimes are of particular interest, as they have all their curvature invariants constant.
Uniqueness of the Fock quantization of scalar fields in spatially flat cosmological spacetimes
Gomar, Laura Castelló; Blas, Daniel Martín-de; Marugán, Guillermo A Mena; Velhinho, José M; 10.1088/1475-7516/2012/11/001
2012-01-01
We study the Fock quantization of scalar fields in (generically) time dependent scenarios, focusing on the case in which the field propagation occurs in --either a background or effective-- spacetime with spatial sections of flat compact topology. The discussion finds important applications in cosmology, like e.g. in the description of test Klein-Gordon fields and scalar perturbations in Friedmann-Robertson-Walker spacetime in the observationally favored flat case. Two types of ambiguities in the quantization are analyzed. First, the infinite ambiguity existing in the choice of a Fock representation for the canonical commutation relations, understandable as the freedom in the choice of inequivalent vacua for a given field. Besides, in cosmological situations, it is customary to scale the fields by time dependent functions, which absorb part of the evolution arising from the spacetime, which is treated classically. This leads to an additional ambiguity, this time in the choice of a canonical pair of field vari...
Anomalous scaling of a scalar field advected by turbulence
Energy Technology Data Exchange (ETDEWEB)
Kraichnan, R.H. [Robert H. Kraichnan, Inc., Santa Fe, NM (United States)
1995-12-31
Recent work leading to deduction of anomalous scaling exponents for the inertial range of an advected passive field from the equations of motion is reviewed. Implications for other turbulence problems are discussed.
Non - Topological Solitons in a Non-minimally Coupled Scalar Field Induced Gravity Theory
Lohiya, Daksh
2016-01-01
Properties of soliton stars that could be expected to naturally arise out of a first order phase transition in non-minimally coupled scalar-field-induced gravity theories are investigated. Of particular interest are configurations, similar to Lee-Wick stars, with vanishing effective gravitational constant in the interiors.
International Nuclear Information System (INIS)
In the framework of a minimal supersymmetric extension of the standard electroweak model, the probability of the processes e→e+γ, e→γ+γ in the intensive electromagnetic field are calculated. The lower bound on the scalar electron mass is found to be M>>60 GeV
Localization of scalar fields in the standing wave braneworld with increasing warp factor
Gogberashvili, Merab; Midodashvili, Levan
2011-01-01
We investigate scalar and tensor fields in the brane model solution for the 5D space-time with standing gravitational waves in the bulk, and show that even in the case of increasing warp factor there exist normalizable zero modes localized on the brane.
Localization of scalar and tensor fields in the standing wave braneworld with increasing warp factor
Energy Technology Data Exchange (ETDEWEB)
Gogberashvili, Merab, E-mail: gogber@gmail.com [Andronikashvili Institute of Physics, 6 Tamarashvili St., Tbilisi 0177 (Georgia); Javakhishvili State University, 3 Chavchavadze Ave., Tbilisi 0128 (Georgia); Midodashvili, Pavle, E-mail: pmidodashvili@yahoo.com [Ilia State University, 3/5 Kakutsa Cholokashvili Ave., Tbilisi 0162 (Georgia); Midodashvili, Levan, E-mail: levmid@hotmail.com [Gori University, 53 Chavchavadze St., Gori 1400 (Georgia)
2011-08-19
We investigate scalar and tensor fields in the brane model solution for the 5D space-time with standing gravitational waves in the bulk and show that even in the case of increasing warp factor there exist normalizable zero modes localized on the brane.
Quasistationary solutions of self-gravitating scalar fields around black holes
Sanchis-Gual, Nicolas; Degollado, Juan Carlos; Montero, Pedro J.; Font, José A.
2015-02-01
Recent perturbative studies have shown the existence of long-lived, quasistationary configurations of scalar fields around black holes. In particular, such configurations have been found to survive for cosmological time scales, which is a requirement for viable dark matter halo models in galaxies based on such types of structures. In this paper we perform a series of numerical relativity simulations of dynamical nonrotating black holes surrounded by self-gravitating scalar fields. We solve numerically the coupled system of equations formed by the Einstein and the Klein-Gordon equations under the assumption of spherical symmetry using spherical coordinates. Our results confirm the existence of oscillating, long-lived, self-gravitating scalar field configurations around nonrotating black holes in highly dynamical spacetimes with a rich scalar field environment. Our numerical simulations are long-term stable and allow for the extraction of the resonant frequencies to make a direct comparison with results obtained in the linearized regime. A by-product of our simulations is the existence of a degeneracy in plausible long-lived solutions of Einstein equations that would induce the same motion of test particles, either with or without the existence of quasibound states.
International Nuclear Information System (INIS)
The chaotic inflationary universe scenario based on a joint account of vacuum polarization and scalar field effects is considered. The probability for the universe to go through the inflationary stage increase compared to that in the separate scenarios. The total expansion during the inflationary stage is equal to the product of the expansions in the separate scenarios. (orig.)
Backreaction of a massless minimally coupled scalar field from inflationary quantum fluctuations
Glavan, D; Prokopec, T.; Prymidis, V.
2014-01-01
In this paper we study a massless, minimally coupled scalar field in a Friedmann-Lemaître-Robertson-Walker space-time with periods of different constant deceleration parameter. We assume the Bunch-Davies vacuum during inflation and then use a sudden matching approximation to match it onto a radiatio
2+1-dimensional wormhole from a doublet of scalar fields
Mazharimousavi, S. Habib; Halilsoy, Mustafa
2015-01-01
We present a class of exact solutions in the framework of (2+1)-dimensional Einstein gravity coupled minimally to a doublet of scalar fields. Our solution can be interpreted upon the tuning of parameters as an asymptotically flat wormhole as well as a particle model in 2+1 dimensions.
Exact radial solution in 2+1 gravity with a real scalar field
International Nuclear Information System (INIS)
In this Letter we give some general considerations about circularly symmetric, static space–times in 2+1 dimensions, focusing first on the surprising (at the time) existence of the BTZ black hole solution. We show that BTZ black holes and Schwarzschild black holes in 3+1 dimensions originate from different definitions of a black hole. There are two by-products of this general discussion: (i) we give a new and simple derivation of (2+1)-dimensional Anti-de Sitter (AdS) space–time; (ii) we present an exact solution to (2+1)-dimensional gravity coupled to a self-interacting real scalar field. The spatial part of the metric of this solution is flat but the temporal part behaves asymptotically like AdS space–time. The scalar field has logarithmic behavior as one would expect for a massless scalar field in flat space–time. The solution can be compared to gravitating scalar field solutions in 3+1 dimensions but with certain oddities connected with the (2+1)-dimensional character of the space–time. The solution is unique to 2+1 dimensions; it does not carry over to 3+1 dimensions
Classical and thermodynamical aspects of black holes with conformally coupled scalar field hair
Winstanley, Elizabeth(Consortium for Fundamental Physics, School of Mathematics and Statistics, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH, United Kingdom)
2004-01-01
We discuss the existence, stability and classical thermodynamics of four-dimensional, spherically symmetric black hole solutions of the Einstein equations with a conformally coupled scalar field. We review the solutions existing in the literature with zero, positive and negative cosmological constant. We also outline new results on the thermodynamics of these black holes when the cosmological constant is non-zero.
Fixed point analysis of a scalar theory with an external field
International Nuclear Information System (INIS)
A momentum dependent projection of the Wegner-Hougton equation is derived for a scalar theory coupled to an external field. This formalism is useful to discuss the phase diagram of the theory. In particular we study some properties of the Gaussian fixed point. copyright 1997 The American Physical Society
Fixed point analysis of a scalar theory with an external field
A. Bonanno; Zappala', D.
1997-01-01
A momentum dependent projection of the Wegner-Hougton equation is derived for a scalar theory coupled to an external field. This formalism is useful to discuss the phase diagram of the theory. In particular we study some properties of the Gaussian fixed point.
On cosmological bounces and Lorentzian wormholes in Galileon theories with extra scalar field
Kolevatov, R
2016-01-01
We study whether it is possible to design a "classical" bouncing cosmology or static spherically symmetric Lorentzian wormhole in cubic Galileon theories interacting with an extra scalar field. We show that bouncing models are always plagued with gradient instabilities, while there are always ghosts in wormhole backgrounds.
Coherent States and Spontaneous Symmetry Breaking in Light Front Scalar Field Theory
Energy Technology Data Exchange (ETDEWEB)
Vary, J.P.; /Iowa State U. /LLNL, Livermore /SLAC; Chakrabarti, D.; /Florida U.; Harindranath, A.; /Saha Inst.; Lloyd, R.; /Arkansas State U.; Martinovic, L.; /Bratislava,; Spence, J.R.; /Iowa State U.
2005-12-14
Recently developed nuclear many-body techniques provide novel results when applied to constituent quark models and to light-front scalar field theory. We show how spontaneous symmetry breaking arises and is consistent with a coherent state ansatz in a variational treatment. The kink and the kink-antikink topological features are identified and the onset of symmetry restoration is demonstrated.
International Nuclear Information System (INIS)
Scattering amplitudes are studied in scalar field theory. The aim of the work carried out is to obtain valid results for all values of the coupling constant, emphasis being given to high energy behavior. A perturbation approach is first presented, the various integral equations are then written in the framework of the multiperipheral and then Bethe-Salpeter models
Confining the scalar field of the Kaluza-Klein wormhole soliton
International Nuclear Information System (INIS)
The Maison five-to-three dimensional reduction, generalized to the case of five-dimensional general relativity with sources, is applied to the problem of confining the scalar field of the Kaluza-Klein wormhole soliton by a very weak perfect fluid source, without affecting the spatial geometry of this localized solution
Barbero-Immirzi parameter as a scalar field: K-inflation from loop quantum gravity?
Taveras, Victor; Yunes, Nicolás
2008-09-01
We consider a loop-quantum gravity inspired modification of general relativity, where the Holst action is generalized by making the Barbero-Immirzi (BI) parameter a scalar field, whose value could be dynamically determined. The modified theory leads to a nonzero torsion tensor that corrects the field equations through quadratic first derivatives of the BI field. Such a correction is equivalent to general relativity in the presence of a scalar field with nontrivial kinetic energy. This stress energy of this field is automatically covariantly conserved by its own dynamical equations of motion, thus satisfying the strong equivalence principle. Every general relativistic solution remains a solution to the modified theory for any constant value of the BI field. For arbitrary time-varying BI fields, a study of cosmological solutions reduces the scalar-field stress energy to that of a pressureless perfect fluid in a comoving reference frame, forcing the scale-factor dynamics to be equivalent to those of a stiff equation of state. Upon ultraviolet completion, this model could provide a natural mechanism for k inflation, where the role of the inflaton is played by the BI field and inflation is driven by its nontrivial kinetic energy instead of a potential.
Barbero-Immirzi parameter as a scalar field: K-inflation from loop quantum gravity?
International Nuclear Information System (INIS)
We consider a loop-quantum gravity inspired modification of general relativity, where the Holst action is generalized by making the Barbero-Immirzi (BI) parameter a scalar field, whose value could be dynamically determined. The modified theory leads to a nonzero torsion tensor that corrects the field equations through quadratic first derivatives of the BI field. Such a correction is equivalent to general relativity in the presence of a scalar field with nontrivial kinetic energy. This stress energy of this field is automatically covariantly conserved by its own dynamical equations of motion, thus satisfying the strong equivalence principle. Every general relativistic solution remains a solution to the modified theory for any constant value of the BI field. For arbitrary time-varying BI fields, a study of cosmological solutions reduces the scalar-field stress energy to that of a pressureless perfect fluid in a comoving reference frame, forcing the scale-factor dynamics to be equivalent to those of a stiff equation of state. Upon ultraviolet completion, this model could provide a natural mechanism for k inflation, where the role of the inflaton is played by the BI field and inflation is driven by its nontrivial kinetic energy instead of a potential.
Relating Double Field Theory to the Scalar Potential of N=2 Gauged Supergravity
Blumenhagen, Ralph; Plauschinn, Erik
2015-01-01
The double field theory action in the flux formulation is dimensionally reduced on a Calabi-Yau three-fold equipped with non-vanishing type IIB geometric and non-geometric fluxes. First, we rewrite the metric-dependent reduced DFT action in terms of quantities that can be evaluated without explicitly knowing the metric on the Calabi-Yau manifold. Second, using properties of special geometry we obtain the scalar potential of N=2 gauged supergravity. After an orientifold projection, this potential is consistent with the scalar potential arising from the flux-induced superpotential, plus an additional D-term contribution.
Unified dark energy and dark matter from a scalar field different from quintessence
Gao, Changjun; Kunz, Martin; Liddle, Andrew R.; Parkinson, David
2009-01-01
We explore unification of dark matter and dark energy in a theory containing a scalar field of non-Lagrangian type, obtained by direct insertion of a kinetic term into the energy-momentum tensor. This scalar is different from quintessence, having an equation of state between -1 and 0 and a zero sound speed in its rest frame. We solve the equations of motion for an exponential potential via a rewriting as an autonomous system, and demonstrate the observational viability of the scenario, for su...
Perepelitsa, Vassili F
2016-01-01
Some features of a Lorentz-violating (but Lorentz-covariant) Lagrangian of a scalar tachyon field are considered in this note. It is shown that the equation of motion and the Feynman propagator resulting from it are Lorentz-invariant, while the Lorentz symmetry of the suggested tachyon field model can be defined as spontaneously broken.
Scalar field probes of power-law space-time singularities
International Nuclear Information System (INIS)
We analyse the effective potential of the scalar wave equation near generic space-time singularities of power-law type (Szekeres-Iyer metrics) and show that the effective potential exhibits a universal and scale invariant leading inverse square behaviour ∼ x-2 in the 'tortoise coordinate' x provided that the metrics satisfy the strict Dominant Energy Condition (DEC). This result parallels obtained for probes consisting of families of massless particles (null geodesic deviation, a.k.a. the Penrose Limit). The detailed properties of the scalar wave operator depend sensitively on the numerical coefficient of the x-2-term, and as one application we show that timelike singularities satisfying the DEC are quantum mechanically singular in the sense of the Horowitz-Marolf (essential self-adjointness) criterion. We also comment on some related issues like the near-singularity behaviour of the scalar fields permitted by the Friedrichs extension
Scalar Field Probes of Power-Law Space-Time Singularities
Blau, Matthias; Weiss, S; Blau, Matthias; Frank, Denis; Weiss, Sebastian
2006-01-01
We analyse the effective potential of the scalar wave equation near generic space-time singularities of power-law type (Szekeres-Iyer metrics) and show that the effective potential exhibits a universal and scale invariant leading x^{-2} inverse square behaviour in the ``tortoise coordinate'' x provided that the metrics satisfy the strict Dominant Energy Condition (DEC). This result parallels that obtained in hep-th/0403252 for probes consisting of families of massless particles (null geodesic deviation, a.k.a. the Penrose Limit). The detailed properties of the scalar wave operator depend sensitively on the numerical coefficient of the x^{-2}-term, and as one application we show that timelike singularities satisfying the DEC are quantum mechanically singular in the sense of the Horowitz-Marolf (essential self-adjointness) criterion. We also comment on some related issues like the near-singularity behaviour of the scalar fields permitted by the Friedrichs extension.
A parametric study on the time scales of the scalar field in turbulent premixed flames
International Nuclear Information System (INIS)
An important new development in modeling premixed turbulent combustion is the use of scalar scales which are directly measurable by experiments. An example of such a model relates the mean reaction rates to the temporal or spatial characteristics of instantaneous flame front crossings. These scalar statistics can be obtained by one- point two-time measurements of the scalar field or by two- dimensional laser tomography. The evolution of these scales through the flame brush is central to this modeling framework since the mean creation rate of products may be directly related to them. The cold flow characteristics are determined by Laser Doppler anemometry. The instantaneous flame structure is explored by one-point laser induced Rayleigh scattering technique. Laser tomography is used to determine some spatial statistics of the investigated flames
Entanglement Growth after a Global Quench in Free Scalar Field Theory
Cotler, Jordan S; Mezei, Márk; Mueller, Mark T
2016-01-01
We compute the entanglement and R\\'enyi entropy growth after a global quench in various dimensions in free scalar field theory. We study two types of quenches: a boundary state quench and a global mass quench. Both of these quenches are investigated for a strip geometry in 1, 2, and 3 spatial dimensions, and for a spherical geometry in 2 and 3 spatial dimensions. We compare the numerical results for massless free scalars in these geometries with the predictions of the analytical quasiparticle model based on EPR pairs, and find excellent agreement in the limit of large region sizes. At subleading order in the region size, we observe an anomalous logarithmic growth of entanglement coming from the zero mode of the scalar.
PDF approach for turbulent scalar field: Some recent developments
Gao, Feng
1993-01-01
The probability density function (PDF) method has been proven a very useful approach in turbulence research. It has been particularly effective in simulating turbulent reacting flows and in studying some detailed statistical properties generated by a turbulent field There are, however, some important questions that have yet to be answered in PDF studies. Our efforts in the past year have been focused on two areas. First, a simple mixing model suitable for Monte Carlo simulations has been developed based on the mapping closure. Secondly, the mechanism of turbulent transport has been analyzed in order to understand the recently observed abnormal PDF's of turbulent temperature fields generated by linear heat sources.
The Barbero-Immirzi Parameter as a Scalar Field: K-Inflation from Loop Quantum Gravity?
Taveras, Victor
2008-01-01
We consider a loop-quantum gravity inspired modification of general relativity, where the Holst action is generalized by making the Barbero-Immirzi (BI) parameter a scalar field, whose value could be dynamically determined. The modified theory leads to a non-zero torsion tensor that corrects the field equations through quadratic first-derivatives of the BI field. Such a correction is equivalent to general relativity in the presence of a scalar field with non-trivial kinetic energy. This stress-energy of this field is automatically covariantly conserved by its own dynamical equations of motion, thus satisfying the strong equivalence principle. Every general relativistic solution remains a solution to the modified theory for any constant value of the BI field. For arbitrary time-varying BI fields, a study of cosmological solutions reduces the scalar field stress-energy to that of a pressureless perfect fluid in a comoving reference frame, forcing the scale factor dynamics to be equivalent to those of a stiff eq...
International Nuclear Information System (INIS)
Exact solutions of the Einstein-Conformally Invariant Scalar Field Equations are obtained for Kantowski-Sachs and Bianchi types I and III cosmologies. The presence of the conformally invariant scalar field is responsible for some interesting features of the solutions. In particular it is found that the Bianchi I model is consistent with the big-bang theory of cosmology. (Author)
Yoshinori, Dobashi; Cingoski, Vlatko; Kaneda, Kazufumi; Yamashita, Hideo; Tomoyuki, Nishita
1998-01-01
Animation of a time-varying 3-D scalar field distribution requires generation of a set of images at a sampled time intervals i.e. frames. Although, volume rendering method can be very advantageous for such 3-D scalar field visualizations, in case of animation, the computation time needed for generation of the entire set of image can be considerably long.
Energy Technology Data Exchange (ETDEWEB)
Karami, K., E-mail: KKarami@uok.ac.i [Department of Physics, University of Kurdistan, Pasdaran St., Sanandaj (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha (Iran, Islamic Republic of); Khaledian, M.S.; Felegary, F.; Azarmi, Z. [Department of Physics, University of Kurdistan, Pasdaran St., Sanandaj (Iran, Islamic Republic of)
2010-03-29
We study the correspondence between the tachyon, K-essence and dilaton scalar field models with the interacting new agegraphic dark energy model in the non-flat FRW universe. We reconstruct the potentials and the dynamics for these scalar field models, which describe accelerated expansion of the universe.
The charged inflaton and its gauge fields: preheating and initial conditions for reheating
Lozanov, Kaloian D
2016-01-01
We calculate particle production during inflation and in the early stages of reheating after inflation in models with a charged scalar field coupled to Abelian and non-Abelian gauge fields. A detailed analysis of the power spectra of primordial electric fields, magnetic fields and charge fluctuations at the end of inflation and preheating is provided. We carefully account for the Gauss constraints during inflation and preheating, and clarify the role of the longitudinal components of the electric field. We calculate the timescale for the back-reaction of the produced gauge fields on the inflaton condensate, marking the onset of non-linear evolution of the fields. We provide a prescription for initial conditions for lattice simulations necessary to capture the subsequent nonlinear dynamics. On the observational side, we find that the primordial magnetic fields generated are too small to explain the origin of magnetic fields on galactic scales and the charge fluctuations are well within observational bounds for...
Zhakatayev, Altay
2016-01-01
In this paper we considered divergence of electric and of magnetic fields for four cases: classical point charge, classical continuous charge, relativistic point and relativistic continuous charges. Results for classical and relativistic point charges are the same as in literature, i.e. Gauss's law is valid. However results for time-varying classical and relativistic distributed charges indicate that divergence of electric field is not zero even for volumes of space where no charges are present. For these cases original Gauss's law might require modification. Divergence of electric field seems to be far-field type scalar anisotropic field, which is generated by time-varying electric charges or currents. Results indicate that for these effects to be sufficiently large to be experimentally observable the time variation of electric charges and/or of currents should be very fast. Divergence of magnetic field is zero for all cases.
Sakalli, I
2016-01-01
Hawking radiation of charged massive spin-0 particles are studied in the gravitational, electromagnetic, dilaton, and axion fields of rotating linear dilaton black holes. In this geometry, we separate the covariant Klein--Gordon equation into radial and angular parts and obtain the exact solutions of both the equations in terms of the confluent Heun functions. Using the radial solution, we analyze the behavior of the wave solutions near the event horizon of the rotating linear dilaton black hole and derive its Hawking radiation spectrum via the Damour--Ruffini--Sannan method.
Matter fields in the lagrangian loop representation scalar QED
Aroca, J M; Fort, H; Siri, R
1995-01-01
We present the extension of the Lagrangian loop gauge invariant representation in such a way to include matter fields. The partition function of lattice compact U(1)-Higgs model is expressed as a sum over closed as much as open surfaces. We have simulated numerically the loop action equivalent to the Villain form of the action and mapped out the beta-gamma phase diagram of this model.
The average action for scalar fields near phase transitions
International Nuclear Information System (INIS)
We compute the average action for fields in two, three and four dimensions, including the effects of wave function renormalization. A study of the one loop evolution equations for the scale dependence of the average action gives a unified picture of the qualitatively different behaviour in various dimensions for discrete as well as abelian and nonabelian continuous symmetry. The different phases and the phase transitions can be infered from the evolution equation. (orig.)
Gravitational coupling of scalar and fermion fields to matter vorticity : microscopic asymmetries
International Nuclear Information System (INIS)
The gravitational coupling of scalar fields and spin-1/2 fermions to matter vorticity is examined; it is considered in the context of Einstein's theory of gravitation and for technical simplicity the Godel model as the gravitational back-ground whose matter content has a non-null vorticity. Scalar field equation and Dirac equation are solved by separation of the field amplitudes into invariant angular-momentum and energy modes. For each case (scalar or Dirac field) these modes provide two distinct complete bases of solutions, which are bases for two representations of the algebra of the total 'angular momentum' of the system (one finite dimensional and the other infinite-dimensional). The presence of a vorticity field of matter generates, via gravitation, microscopic asymmetries in the physics of fermions. The 'angular-momentum' vector space appears to be polarized along the direction determined by the local vorticity Ω sup(→). Microscopic currents are asymmetric along the direction determined by the vorticity field: fermions (antifermions) currents are larger along the direction antiparallel (parallel) to the vorticity field. This current asymmetry as well other parity violating effects (for example, a split of mass for fermions) can in principle be used in devising experiments to detect the presence of a cosmological rotation of the universe, its direction and intensity. In case of production of pairs under CP violation a net number asymmetry may be generated between fermions and antifermions. (Author)
Hamiltonian description of the parametrized scalar field in bounded spatial regions
G., J Fernando Barbero; Villaseñor, Eduardo J S
2015-01-01
We study the Hamiltonian formulation for a parametrized scalar field in a regular bounded spatial region subject to Dirichlet, Neumann and Robin boundary conditions. We generalize the work carried out by a number of authors on parametrized field systems to the interesting case where spatial boundaries are present. The configuration space of our models contains both smooth scalar fields defined on the spatial manifold and spacelike embeddings from the spatial manifold to a target spacetime endowed with a fixed Lorentzian background metric. We pay particular attention to the geometry of the infinite dimensional manifold of embeddings and the description of the relevant geometric objects: the symplectic form on the primary constraint submanifold and the Hamiltonian vector fields defined on it.
Hamiltonian description of the parametrized scalar field in bounded spatial regions
Barbero G, J. Fernando; Margalef-Bentabol, Juan; Villaseñor, Eduardo J. S.
2016-05-01
We study the Hamiltonian formulation for a parametrized scalar field in a regular bounded spatial region subject to Dirichlet, Neumann and Robin boundary conditions. We generalize the work carried out by a number of authors on parametrized field systems to the interesting case where spatial boundaries are present. The configuration space of our models contains both smooth scalar fields defined on the spatial manifold and spacelike embeddings from the spatial manifold to a target spacetime endowed with a fixed Lorentzian background metric. We pay particular attention to the geometry of the infinite dimensional manifold of embeddings and the description of the relevant geometric objects: the symplectic form on the primary constraint submanifold and the Hamiltonian vector fields defined on it.
A sensitive search for dark energy through chameleon scalar fields using neutron interferometry
International Nuclear Information System (INIS)
The physical origin of the dark energy, which is postulated to cause the accelerated expansion rate of the universe, is one of the major open questions of cosmology. A large subset of theories postulate the existence of a scalar field with a nonlinear coupling to matter chosen so that the effective range and/or strength of the field is greatly suppressed unless the source is placed in vacuum. We describe a measurement using neutron interferometry which can place a stringent upper bound on chameleon fields proposed as a solution to the problem of the origin of dark energy of the universe in the regime with a strongly-nolinear coupling term. In combination with other experiments searching for exotic short-range forces and laser-based measurements, slow neutron experiments are capable of eliminating this and many similar types of scalar-field-based dark energy models by laboratory experiments
Vacuum energy density and pressure of a massive scalar field
Mera, Fernando Daniel; Fulling, S. A.
2014-01-01
With a view toward application of the Pauli-Villars regularization method to the Casimir energy of boundaries, we calculate the expectation values of the components of the stress tensor of a confined massive field in 1+1 space-time dimensions. Previous papers by Hays and Fulling are bridged and generalized. The Green function for the time-independent Schrodinger equation is constructed from the Green function for the whole line by the method of images; equivalently, the one-dimensional system...
D'Ambroise, Jennie
2010-01-01
We show that Einstein's gravitational field equations for the Friedmann-Robertson-Lema\\^itre-Walker (FRLW) and for two conformal versions of the Bianchi I and Bianchi V perfect fluid scalar field cosmological models, can be equivalently reformulated in terms of a single equation of either generalized Ermakov-Milne-Pinney (EMP) or (non)linear Schr\\"odinger (NLS) type. This work generalizes or presents an alternative to similar reformulations published by the authors who inspired this thesis: R...
Efficient, Decentralized Detection of Qualitative Spatial Events in a Dynamic Scalar Field
Myeong-Hun Jeong; Matt Duckham
2015-01-01
This paper describes an efficient, decentralized algorithm to monitor qualitative spatial events in a dynamic scalar field. The events of interest involve changes to the critical points (i.e., peak, pits and passes) and edges of the surface network derived from the field. Four fundamental types of event (appearance, disappearance, movement and switch) are defined. Our algorithm is designed to rely purely on qualitative information about the neighborhoods of nodes in the sensor network and doe...
Dispersion relations and entropy of scalar fields in Rindler and de Sitter spaces
Lenz, F; Yazaki, K
2014-01-01
Properties of scalar fields in Rindler and de Sitter spaces are the subject of this work. Using the "brick wall model'' the dispersion relations are determined and the remarkable properties common to both spaces as well as their differences are discussed. Equipped with these tools the horizon induced thermodynamics is revisited and shown to be dominated by a single mode propagating perpendicular to the horizon. Explicit expressions for the partition function, entropy and heat capacity for massless and massive fields are presented.
Magnetic Pressure as a Scalar Representation of Field Effects in Magnetic Suspensions
Zborowski, Maciej; Moore, Lee R.; Williams, P. Stephen; Chalmers, Jeffrey J.
2010-01-01
Magnetic microsphere suspensions undergo complex motion when exposed to finite sources of the magnetic field, such as small permanent magnets. The computational complexity is compounded by a difficulty in choosing a suitable choice of visualization tools because this often requires using the magnetic force vector field in three dimensions. Here we present a potentially simpler approach by using the magnetic pressure. It is a scalar quantity, pm = B2/2μ0, and its usefulness has been already de...
Carvalho, F. C.; de Mello, E. R. Bezerra
2000-01-01
In this paper we calculate the effects produced by temperature in the renormalized vaccum expectation value of the square of the massless scalar field in the pointlike global monopole spacetime. In order to develop this calculation, we had to construct the Euclidean thermal Green function associated with this field in this background. We also calculate the high-temperature limit for the thermal average of the zero-zero component of the energy-momentum tensor.