Showing papers on "Scalar potential published in 2010"
TL;DR: In this article, the authors studied the thermodynamics of magnetically charged branes in a dilaton-axion system with electric and magnetic charges in asymptotically anti de Sitter space.
Abstract: We study black branes carrying both electric and magnetic charges in Einstein-Maxwell theory coupled to a dilaton-axion in asymptotically anti de Sitter space. After reviewing and extending earlier results for the case of electrically charged branes, we characterise the thermodynamics of magnetically charged branes. We then focus on dyonic branes in theories which enjoy an SL(2,R) electric-magnetic duality. Using SL(2,R), we are able to generate solutions with arbitrary charges starting with the electrically charged solution, and also calculate transport coefficients. These solutions all exhibit a Lifshitz-like near-horizon geometry. The system behaves as expected for a charged fluid in a magnetic field, with non-vanishing Hall conductance and vanishing DC longitudinal conductivity at low temperatures. Its response is characterised by a cyclotron resonance at a frequency proportional to the magnetic field, for small magnetic fields. Interestingly, the DC Hall conductance is related to the attractor value of the axion. We also study the attractor flows of the dilaton-axion, both in cases with and without an additional modular-invariant scalar potential. The flows exhibit intricate behaviour related to the duality symmetry. Finally, we briefly discuss attractor flows in more general dilaton-axion theories which do not enjoy SL(2,R) symmetry.
245 citations
TL;DR: In this article, a modified Newtonian dynamics (MOND) as a modified-potential theory of gravity is proposed, where the MOND potential φ produced by a mass distribution ρ is a solution of the Poisson equation for the modified source density ˆ ρ =− (4πG) −1 ∇· g, where g = ν(|g N |/a0)g N, and g N is the Newtonian acceleration field of ρ.
Abstract: A new formulation of modified Newtonian dynamics (MOND) as a modified-potential theory of gravity is propounded. In effect, the theory dictates that the MOND potential φ produced by a mass distribution ρ is a solution of the Poisson equation for the modified source density ˆ ρ =− (4πG) −1 ∇· g, where g = ν(|g N |/a0)g N , and g N is the Newtonian acceleration field of ρ. This makes φ simply the scalar potential of the algebraic acceleration field g. The theory thus involves solving only linear-differential equations, with one non-linear, algebraic step. It is derivable from an action, satisfies all the usual conservation laws, and gives the correct centre-of-mass acceleration to composite bodies. The theory is akin in some respects to the non-linear Poisson formulation of Bekenstein and Milgrom, but it is different from it, and is obviously easier to apply. The two theories are shown to emerge as natural modifications of a Palatini-type formulation of Newtonian gravity, and are members in a larger class of bi-potential theories.
189 citations
TL;DR: In this paper, the scalar potential of a D3-brane in a warped conifold region of a compactification with stabilized moduli was studied, and the authors provided an approach in which Planck-suppressed contributions to the D3brane effective action can be computed.
Abstract: We give a comprehensive treatment of the scalar potential for a D3-brane in a warped conifold region of a compactification with stabilized moduli. By studying general ultraviolet perturbations in supergravity, we systematically incorporate ‘compactification effects’ sourced by supersymmetry breaking in the compact space. Significant contributions to the D3-brane potential, including the leading term in the infrared, arise from imaginary anti-self-dual (IASD) fluxes. For an arbitrary Calabi-Yau cone, we determine the most general IASD fluxes in terms of scalar harmonics, then compute the resulting D3-brane potential. Specializing to the conifold, we identify the operator dual to each mode of flux, and for chiral operators we confirm that the potential computed in the gauge theory matches the gravity result. The effects of four-dimensional curvature, including the leading D3-brane mass term, arise directly from the ten-dimensional equations of motion. Furthermore, we show that gaugino condensation on D7-branes provides a local source for IASD flux. This flux automatically and precisely encodes the nonperturbative contributions to the D3-brane potential, yielding a promising ten-dimensional representation of four-dimensional nonperturbative effects. Our result encompasses all significant contributions to the D3-brane potential discussed in the literature, and does so in the single coherent framework of ten-dimensional supergravity. Moreover, we identify new terms with irrational scaling dimensions that were inaccessible in prior works. By decoupling gravity in a noncompact configuration, then systematically reincorporating compactification effects as ultraviolet perturbations, we have provided an approach in which Planck-suppressed contributions to the D3-brane effective action can be computed. This is the companion paper to [1].
161 citations
TL;DR: In this paper, the scalar potential of a D3-brane in a warped conifold region of a compactification with stabilized moduli was studied, including the effects of four-dimensional curvature.
Abstract: We give a comprehensive treatment of the scalar potential for a D3-brane in a warped conifold region of a compactification with stabilized moduli. By studying general ultraviolet perturbations in supergravity, we systematically incorporate `compactification effects' sourced by supersymmetry breaking in the compact space. Significant contributions to the D3-brane potential, including the leading term in the infrared, arise from imaginary anti-self-dual (IASD) fluxes. For an arbitrary Calabi-Yau cone, we determine the most general IASD fluxes in terms of scalar harmonics, then compute the resulting D3-brane potential. Specializing to the conifold, we identify the operator dual to each mode of flux, and for chiral operators we confirm that the potential computed in the gauge theory matches the gravity result. The effects of four-dimensional curvature, including the leading D3-brane mass term, arise directly from the ten-dimensional equations of motion. Furthermore, we show that gaugino condensation on D7-branes provides a local source for IASD flux. This flux precisely encodes the nonperturbative contributions to the D3-brane potential, yielding a promising ten-dimensional representation of four-dimensional nonperturbative effects. Our result encompasses all significant contributions to the D3-brane potential discussed in the literature, and does so in the single coherent framework of ten-dimensional supergravity. Moreover, we identify new terms with irrational scaling dimensions that were inaccessible in prior works. By decoupling gravity in a noncompact configuration, then systematically reincorporating compactification effects as ultraviolet perturbations, we have provided an approach in which Planck-suppressed contributions to the D3-brane effective action can be computed.
155 citations
TL;DR: In this article, an extension of the standard model with a complex singlet scalar field and scale invariance at the tree level is presented. But the model is explicitly broken by quantum corrections, which can trigger electroweak symmetry breaking and provide a mechanism for solving the gauge hierarchy problem.
Abstract: We perform a systematic analysis of an extension of the Standard Model that includes a complex singlet scalar field and is scale invariant at the tree level. We call such a model the Minimal Scale Invariant extension of the Standard Model (MSISM). The tree-level scale invariance of the model is explicitly broken by quantum corrections, which can trigger electroweak symmetry breaking and potentially provide a mechanism for solving the gauge hierarchy problem. Even though the scale invariant Standard Model is not a realistic scenario, the addition of a complex singlet scalar field may result in a perturbative and phenomenologically viable theory. We present a complete classification of the flat directions which may occur in the classical scalar potential of the MSISM. After calculating the one-loop effective potential of the MSISM, we investigate a number of representative scenarios and determine their scalar boson mass spectra, as well as their perturbatively allowed parameter space compatible with electroweak precision data. We discuss the phenomenological implications of these scenarios, in particular, whether they realize explicit or spontaneous CP violation, neutrino masses or provide dark matter candidates. In particular, we find a new minimal scale-invariant model of maximal spontaneous CP violation which can stay perturbative up to Planck-mass energy scales, without introducing an unnaturally large hierarchy in the scalar-potential couplings.
132 citations
TL;DR: In this paper, an extension of the standard model with a complex singlet scalar field and scale invariance at the tree level is presented. But the model is explicitly broken by quantum corrections, which can trigger electroweak symmetry breaking and provide a mechanism for solving the gauge hierarchy problem.
Abstract: We perform a systematic analysis of an extension of the Standard Model that includes a complex singlet scalar field and is scale invariant at the tree level. We call such a model the Minimal Scale Invariant extension of the Standard Model (MSISM). The tree-level scale invariance of the model is explicitly broken by quantum corrections, which can trigger electroweak symmetry breaking and potentially provide a mechanism for solving the gauge hierarchy problem. Even though the scale invariant Standard Model is not a realistic scenario, the addition of a complex singlet scalar field may result in a perturbative and phenomenologically viable theory. We present a complete classification of the flat directions which may occur in the classical scalar potential of the MSISM. After calculating the one-loop effective potential of the MSISM, we investigate a number of representative scenarios and determine their scalar boson mass spectra, as well as their perturbatively allowed parameter space compatible with electroweak precision data. We discuss the phenomenological implications of these scenarios, in particular, whether they realize explicit or spontaneous CP violation, neutrino masses or provide dark matter candidates. In particular, we find a new minimal scale-invariant model of maximal spontaneous CP violation which can stay perturbative up to Planck-mass energy scales, without introducing an unnaturally large hierarchy in the scalar-potential couplings.
110 citations
TL;DR: In this article, a soft-wall anti-de Sitter/QCD model with a modified five-dimensional metric at the infrared region is constructed to obtain a nontrivial dilaton solution, which incorporates the chiral symmetry breaking and linear confinement.
Abstract: A soft-wall anti-de Sitter/QCD model with a modified five-dimensional metric at the infrared region is constructed to obtain a nontrivial dilaton solution, which incorporates the chiral symmetry breaking and linear confinement. By taking the pion mass and decay constant as two input mass scales, the resulting predictions for the resonance states of pseudoscalar, scalar, vector, and axial-vector mesons agree remarkably with the experimentally confirmed resonance states. The effects of the quartic interaction term are investigated by taking an appropriate sign and magnitude for maintaining the stability of the bulk scalar potential. It is shown that such a simply modified soft-wall anti-de Sitter/QCD model can lead to a consistent prediction for the mass spectra of resonance states in the pseudoscalar, scalar, vector, and axial-vector mesons; the agreement with the experimental data is found to be better than 10% for the excited meson states. The resulting pion form factor also agrees well with the experimental data.
104 citations
TL;DR: In this paper, the authors explore the cosmic evolution of a scalar field with the kinetic term coupled to the Einstein tensor and find that, in the absence of other matter sources or in the presence of only pressureless matter, the scalar behaves as pressureless material and the sound speed of the scalars is vanishing.
Abstract: We explore the cosmic evolution of a scalar field with the kinetic term coupled to the Einstein tensor. We find that, in the absence of other matter sources or in the presence of only pressureless matter, the scalar behaves as pressureless matter and the sound speed of the scalar is vanishing. These properties enable the scalar field to be a candidate of cold dark matter. By also considering the scalar potential, we find the scalar field may play the role of both dark matter and dark energy. In this case, the equation of state of the scalar can cross the phantom divide, but this can lead to the sound speed becoming superluminal as it crosses the divide, and so is physically forbidden. Finally, if the kinetic term is coupled to more than one Einstein tensor, we find the equation of state is always approximately equal to -1 whether the potential is flat or not, and so the scalar may also be a candidate for the inflaton.
95 citations
TL;DR: In this paper, a scalar field with kinetic term coupled to itself and to the curvature was studied as a source of dark energy, and the role of this new coupling in the accelerated expansion at large times was analyzed.
Abstract: We study a scalar field with kinetic term coupled to itself and to the curvature, as a source of dark energy, and analyze the role of this new coupling in the accelerated expansion at large times. In the case of scalar field dominance, the scalar field and potential giving rise to power-law expansion are found in some cases, and a dynamical equation of state is calculated for a given solution of the field equations. A behavior very close to that of the cosmological constant was found
88 citations
TL;DR: In this paper, the phenomenological consequences of requiring the cancellation of quadratic divergences up to the leading two-loop order within the two-Higgs-doublet model are discussed.
Abstract: We discuss the phenomenological consequences of requiring the cancellation of quadratic divergences up to the leading two-loop order within the two-Higgs-doublet model. Taking into account existing experimental constraints, allowed regions in the parameter space, permitting the cancellation, are determined. A degeneracy between masses of scalar bosons is observed for tanβ ≳ 40. The possibility for CP violation in the scalar potential is discussed and regions of tanβ-M H ± with a substantial amount of CP violation are determined. In order to provide a source for dark matter in a minimal manner, a scalar gauge singlet is introduced and discussed. The model allows to ameliorate the little hierarchy problem by lifting the minimal scalar Higgs-boson mass and by suppressing the quadratic corrections to scalar masses. The cutoff originating from the naturality arguments is therefore lifted from ~0.6 TeV in the standard model to ≳ 2.5 TeV in two-Higgs-doublet model depending on the mass of the lightest scalar.
83 citations
TL;DR: In this paper, the authors considered asymptotically anti de Sitter gravity coupled to a scalar field with mass slightly above the Breitenlohner-Freedman bound and showed that the energy remains bounded even in some cases where W can become arbitrarily negative.
Abstract: We consider asymptotically anti de Sitter gravity coupled to a scalar field with mass slightly above the Breitenlohner–Freedman bound. This theory admits a large class of consistent boundary conditions characterized by an arbitrary function W. An important open question is to determine which W admit stable ground states. It has previously been shown that the total energy is bounded from below if W is bounded from below, and the bulk scalar potential V() admits a suitable superpotential. We extend this result and show that the energy remains bounded even in some cases where W can become arbitrarily negative. As one application, this leads to the possibility that in gauge/gravity duality, one can add a double trace operator with negative coefficient to the dual field theory and still have a stable vacuum.
TL;DR: In this article, the necessary and sufficient condition for a class of noncanonical single scalar field models to be exactly equivalent to barotropic perfect fluids, under the assumption of an irrotational fluid flow, was obtained.
Abstract: In this brief report, we obtain the necessary and sufficient condition for a class of noncanonical single scalar field models to be exactly equivalent to barotropic perfect fluids, under the assumption of an irrotational fluid flow. An immediate consequence of this result is that the nonadiabatic pressure perturbation in this class of scalar field systems vanishes exactly at all orders in perturbation theory and on all scales. The Lagrangian for this general class of scalar field models depends on both the kinetic term and the value of the field. However, after a field redefinition, it can be effectively cast in the form of a purely kinetic k-essence model.
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TL;DR: In this article, the authors deal with F(T) gravity models driven by real scalar fields with usual and phantom dynamics, and find some analytical solutions for scale factors and scalar field.
Abstract: This work deals with F(T) gravity models driven by real scalar fields with usual and phantom dynamics. We illustrate the results with examples of current interest, and we find some analytical solutions for scale factors and scalar fields. The results indicate that torsionscalar models also admit the accelerated expansion of the universe.
TL;DR: In this article, the authors explore the cosmic evolution of a scalar field with the kinetic term coupled to the Einstein tensor and find that, in the absence of other matter sources or in the presence of only pressureless matter, the scalar behaves as pressureless material and the sound speed of the scalars is vanishing.
Abstract: We explore the cosmic evolution of a scalar field with the kinetic term coupled to the Einstein tensor. We find that, in the absence of other matter sources or in the presence of only pressureless matter, the scalar behaves as pressureless matter and the sound speed of the scalar is vanishing. These properties enable the scalar field to be a candidate of cold dark matter. By also considering the scalar potential, we find the scalar field may play the role of both dark matter and dark energy. In this case, the equation of state of the scalar can cross the phantom divide, but this can lead to the sound speed becoming superluminal as it crosses the divide, and so is physically forbidden. Finally, if the kinetic term is coupled to more than one Einstein tensor, we find the equation of state is always approximately equal to -1 whether the potential is flat or not, and so the scalar may also be a candidate for the inflaton.
TL;DR: In this article, a new ring-shaped non-harmonic oscillator potential is proposed and the precise bound solution of Dirac equation with the potential is gained when the scalar potential is equal to the vector potential.
Abstract: A new ring-shaped non-harmonic oscillator potential is proposed. The precise bound solution of Dirac equation with the potential is gained when the scalar potential is equal to the vector potential. The angular equation and radial equation are obtained through the variable separation method. The results indicate that the normalized angle wave function can be expressed with the generalized associated-Legendre polynomial, and the normalized radial wave function can be expressed with confluent hypergeometric function. And then the precise energy spectrum equations are obtained. The ground state and several low excited states of the system are solved. And those results are compared with the non-relativistic effect energy level in Phys. Lett. A 340 (2005) 94. The positive energy states of system are discussed and the conclusions are made properly.
TL;DR: In this paper, the authors used a "poloidal-toroidal decomposition" (PTD) of the time derivative of the vector magnetic field to estimate the photospheric electric field.
Abstract: Determining the electric field distribution on the Sun's photosphere is essential for quantitative studies of how energy flows from the Sun's photosphere, through the corona, and into the heliosphere. This electric field also provides valuable input for data-driven models of the solar atmosphere and the Sun-Earth system. We show how observed vector magnetogram time series can be used to estimate the photospheric electric field. Our method uses a "poloidal-toroidal decomposition" (PTD) of the time derivative of the vector magnetic field. These solutions provide an electric field whose curl obeys all three components of Faraday's Law. The PTD solutions are not unique; the gradient of a scalar potential can be added to the PTD electric field without affecting consistency with Faraday's Law. We then present an iterative technique to determine a potential function consistent with ideal MHD evolution; but this field is also not a unique solution to Faraday's Law. Finally, we explore a variational approach that minimizes an energy functional to determine a unique electric field, a generalization of Longcope's "Minimum Energy Fit." The PTD technique, the iterative technique, and the variational technique are used to estimate electric fields from a pair of synthetic vector magnetograms taken from an MHD simulation; and these fields are compared with the simulation's known electric fields. The PTD and iteration techniques compare favorably to results from existing velocity inversion techniques. These three techniques are then applied to a pair of vector magnetograms of solar active region NOAA AR8210, to demonstrate the methods with real data. Careful examination of the results from all three methods indicates that evolution of the magnetic vector by itself does not provide enough information to determine the true electric field in the photosphere. Either more information from other measurements, or physical constraints other than those considered here are necessary to find the true electric field. However, we show it is possible to construct physically reasonable electric field distributions whose curl matches the evolution of all three components of B. We also show that the horizontal and vertical Poynting flux patterns derived from the three techniques are similar to one another for the cases investigated.
TL;DR: The condition under which an electron beam incident on an SL is highly collimated along its direction is determined, and the effect of spatially separated potential and magnetic δ-function barriers is investigated and a better collimation in specific cases is predicted.
Abstract: We consider a one-dimensional (1D) superlattice (SL) on graphene consisting of very high and very thin (δ-function) magnetic and potential barriers with zero average potential and zero magnetic field. We calculate the energy spectrum analytically, study it in different limiting cases, and determine the condition under which an electron beam incident on an SL is highly collimated along its direction. In the absence of the magnetic SL the collimation is very sensitive to the value of W/Ws and is optimal for W/Ws = 1, where W is the distance between the positive and negative barriers and L = W + Ws is the size of the unit cell. In the presence of only the magnetic SL the collimation decreases and the symmetry of the spectrum around ky is broken for . In addition, a gap opens which depends on the strength of the magnetic field. We also investigate the effect of spatially separated potential and magnetic δ-function barriers and predict a better collimation in specific cases.
TL;DR: In this article, the inflaton scalar potential is used to compute the (CMB) observables of inflation, associated with curvature perturbations (namely, the scalar and tensor spectral indices, and the tensor-to-scalar ratio).
Abstract: We revisit the old (fourth-order or quadratically generated) gravity model of Starobinsky in four space-time dimensions, and derive the (inflaton) scalar potential in the equivalent scalar-tensor gravity model. The inflaton scalar potential is used to compute the (CMB) observables of inflation, associated with curvature perturbations (namely, the scalar and tensor spectral indices, and the tensor-to-scalar ratio), including the new next-to-leading-order terms with respect to the inverse number of e-foldings. The results are compared to the recent (WMAP5) experimental bounds. We confirm both mathematical and physical equivalence between f(R) gravity theories and the corresponding scalar-tensor gravity theories.
TL;DR: In this paper, the authors constructed the N = 6 conformal supergravity in three dimensions from a set of Chern-Simons-like terms one for each of the graviton, gravitino, and R-symmetry gauge field and then couple this theory to the n = 6 superconformal ABJM theory.
Abstract: In this paper we construct the N = 6 conformal supergravity in three dimensions from a set of Chern-Simons-like terms one for each of the graviton, gravitino, and R-symmetry gauge field and then couple this theory to the N = 6 superconformal ABJM theory. In a first step part of the coupled Lagrangian for this topologically gauged ABJM theory is derived by demanding that all terms of third and second order in covariant derivatives cancel in the supersymmtry variation of the Lagrangian. To achieve this the transformation rules of the two separate sectors must be augmented by new terms. In a second step we analyze all terms in delta L that are of first order in covariant derivatives. The cancelation of these terms require additional terms in the transformation rules as well as a number of new terms in the Lagrangian. As a final step we check that all remaining terms in dL which are bilinear in fermions cancel which means that the presented Lagrangian and transformation rules constitute the complete answer. In particular we find in the last step new terms in the scalar potential containing either one or no structure constant. The non-derivative higher fermion terms in delta L that have not yet been completely analyzed are briefly discussed in the Conclusions. A possible connection to chiral gravity is also mentioned there.
TL;DR: In this paper, the authors consider an extension of the Standard Model in which the symmetry is enlarged by a global flavour factor A4 and the scalar sector accounts for three copies of the Higgs, transforming as a triplet of A4.
Abstract: We consider an extension of the Standard Model in which the symmetry is enlarged by a global flavour factor A4 and the scalar sector accounts for three copies of the Standard Model Higgs, transforming as a triplet of A4. In this context, we study the most general scalar potential and its minima, performing for each of them a model independent analysis on the related phenomenology. We study the scalar spectrum, the new contributions to the oblique corrections, the decays of the Z and W, the new sources of flavour violation, which all are affected by the introduction of multiple Higgses transforming under A4. We find that this model independent approach discriminates the different minima allowed by the scalar potential.
TL;DR: In this article, the authors studied the thermodynamics of magnetically charged branes in a dilaton-axion system with electric and magnetic charges in asymptotically anti-de Sitter space and showed that the system behaves as expected for a charged fluid in a magnetic field.
Abstract: We study black branes carrying both electric and magnetic charges in Einstein-Maxwell theory coupled to a dilaton-axion in asymptotically anti de Sitter space. After reviewing and extending earlier results for the case of electrically charged branes, we characterise the thermodynamics of magnetically charged branes. We then focus on dyonic branes in theories which enjoy an $SL(2,R)$ electric-magnetic duality. Using $SL(2,R)$, we are able to generate solutions with arbitrary charges starting with the electrically charged solution, and also calculate transport coefficients. These solutions all exhibit a Lifshitz-like near-horizon geometry. The system behaves as expected for a charged fluid in a magnetic field, with non-vanishing Hall conductance and vanishing DC longitudinal conductivity at low temperatures. Its response is characterised by a cyclotron resonance at a frequency proportional to the magnetic field, for small magnetic fields. Interestingly, the DC Hall conductance is related to the attractor value of the axion. We also study the attractor flows of the dilaton-axion, both in cases with and without an additional modular-invariant scalar potential. The flows exhibit intricate behaviour related to the duality symmetry. Finally, we briefly discuss attractor flows in more general dilaton-axion theories which do not enjoy $SL(2,R)$ symmetry.
TL;DR: In this article, the authors consider Friedmann-Lemaitre-Robertson-Walker flat cosmological models in the framework of general Jordan frame scalar-tensor theories of gravity with arbitrary coupling functions.
Abstract: We consider Friedmann-Lemaitre-Robertson-Walker flat cosmological models in the framework of general Jordan frame scalar-tensor theories of gravity with arbitrary coupling functions, in the era when the energy density of the scalar potential dominates over the energy density of ordinary matter. We focus upon the phase space of the scalar field. To study the regime suggested by the local weak field tests (i.e. close to the so-called limit of general relativity) we propose a nonlinear approximation scheme, solve for the phase trajectories, and provide a complete classification of possible phase portraits. We argue that the topology of trajectories in the nonlinear approximation is representative of those of the full system, and thus can tell for which scalar-tensor models general relativity functions as an attractor.
01 May 2010
TL;DR: In this article, the authors used a "poloidal-toroidal decomposition" (PTD) of the time derivative of the vector magnetic field to estimate the photospheric electric field.
Abstract: Determining the electric field distribution on the Sun's photosphere is essential for quantitative studies of how energy flows from the Sun's photosphere, through the corona, and into the heliosphere. This electric field also provides valuable input for data-driven models of the solar atmosphere and the Sun-Earth system. We show how observed vector magnetogram time series can be used to estimate the photospheric electric field. Our method uses a "poloidal-toroidal decomposition" (PTD) of the time derivative of the vector magnetic field. These solutions provide an electric field whose curl obeys all three components of Faraday's Law. The PTD solutions are not unique; the gradient of a scalar potential can be added to the PTD electric field without affecting consistency with Faraday's Law. We then present an iterative technique to determine a potential function consistent with ideal MHD evolution; but this field is also not a unique solution to Faraday's Law. Finally, we explore a variational approach that minimizes an energy functional to determine a unique electric field, a generalization of Longcope's "Minimum Energy Fit." The PTD technique, the iterative technique, and the variational technique are used to estimate electric fields from a pair of synthetic vector magnetograms taken from an MHD simulation; and these fields are compared with the simulation's known electric fields. The PTD and iteration techniques compare favorably to results from existing velocity inversion techniques. These three techniques are then applied to a pair of vector magnetograms of solar active region NOAA AR8210, to demonstrate the methods with real data. Careful examination of the results from all three methods indicates that evolution of the magnetic vector by itself does not provide enough information to determine the true electric field in the photosphere. Either more information from other measurements, or physical constraints other than those considered here are necessary to find the true electric field. However, we show it is possible to construct physically reasonable electric field distributions whose curl matches the evolution of all three components of B. We also show that the horizontal and vertical Poynting flux patterns derived from the three techniques are similar to one another for the cases investigated.
TL;DR: In this paper, a spatial circular harmonic expansion of the magnetic scalar potential is used to reduce the effects of external magnetic fields on the accuracy of magnetic sensor measurements used for the reconstruction of ac electric currents flowing in massive parallel conductors.
Abstract: In order to reduce the effects of external magnetic fields on the accuracy of magnetic sensor measurements used for the reconstruction of ac electric currents flowing in massive parallel conductors, we use a spatial circular harmonic expansion of the magnetic scalar potential. Thanks to the linearity of the magnetic field problem with respect to the sources, we can then apply the least squares inversion and obtain the set of currents from the knowledge of the magnetic field data collected by the sensor array in the vicinity of the current carrying conductors. Furthermore, we can optimize the positions and the orientations of the magnetic sensors using D-optimality theory and particle swarm optimization.
TL;DR: In this paper, the inflaton scalar potential is derived for the scalar-tensor gravity model via a Legendre-Weyl transform. And the results are compared to the recent (WMAP5) experimental bounds.
Abstract: We revisit the old (fourth-order or quadratically generated) gravity model of Starobinsky in four space-time dimensions, and derive the (inflaton) scalar potential in the equivalent scalar-tensor gravity model via a Legendre-Weyl transform. The inflaton scalar potential is used to compute the (CMB) observables of inflation associated with curvature perturbations (namely, the scalar and tensor spectral indices, and the tensor-to-scalar ratio), including the new next-to-leading-order terms with respect to the inverse number of e-foldings. The results are compared to the recent (WMAP5) experimental bounds. We confirm both mathematical and physical equivalence between f(R) gravity theories and the corresponding scalar-tensor gravity theories.
TL;DR: In this article, a comparative study of numerical methods of analysis of electromagnetic fields is presented, focusing on the finite element method (FEM) and finite integration technique (FIT), but with the cell and equivalent network approaches also considered.
Abstract: The paper offers a comparative study of numerical methods of analysis of electromagnetic fields. The focus is on the finite element method (FEM) and finite integration technique (FIT), but with the cell and equivalent network approaches also considered. It is shown how the approximate integrals describing coefficients of the FEM need to be derived for a mesh with parallelepiped elements to achieve consistency with FIT equations. The equivalence of FEM and FIT formulations for a triangular mesh in 2D is highlighted. The TEAM Workshops Problem No. 7 is used as an example for numerical comparisons. Two formulations have been considered: 1) using the edge values of the magnetic vector potential A and the nodal values of the electric scalar potential V; and 2) expressed in terms of the edge values of both magnetic A and electric T-T0 vector potentials.
09 May 2010
TL;DR: In this article, the vector potential formulation applied to static problems is developed and compared to the scalar potential one, previously developed, and two potential formulations can be used in the stochastic case.
Abstract: Stochastic spectral finite-element method can be used to take into account some random aspects in the input data (material characteristic, source terms) involved in static electromagnetism problems. Similarly to the deterministic case, two potential formulations can be used in the stochastic case. The vector potential formulation applied to static problems is developed and compared to the scalar potential one, previously developed.
TL;DR: In this article, the toy-model of topological inflation, based on the R 4 -modified gravity, was revisited and its equivalence to the certain scalar-tensor gravity model in four spacetime dimensions was computed.
Abstract: We reconsider the toy-model of topological inflation, based on the R 4 -modified gravity. By using its equivalence to the certain scalar-tensor gravity model in four spacetime dimensions, we compute the inflaton scalar potential and investigate a possibility of inflation. We confirm the existence of the slow-roll inflation with an exit. However, the model suffers from the �-problem that gives rise to the unacceptable value of the spectral index ns of scalar perturbations.
TL;DR: By using a new parametrization of the dilaton field and including a cubic term in the bulk scalar potential, the authors realized linear confinement in both meson and nucleon sectors within the framework of soft-wall AdS/QCD.
Abstract: By using a new parametrization of the dilaton field and including a cubic term in the bulk scalar potential, we realize linear confinement in both meson and nucleon sectors within the framework of soft-wall AdS/QCD. At the same time this model also correctly incorporate chiral symmetry breaking. We compare our resulting mass spectra with experimental data and find good agreement between them.
TL;DR: In this paper, a toy model of topological inflation, based on the R4 modified gravity, was considered and its equivalence to a certain scalar-tensor gravity model in four spacetime dimensions was computed.
Abstract: We reconsider a toy model of topological inflation, based on the R4-modified gravity. By using its equivalence to a certain scalar–tensor gravity model in four spacetime dimensions, we compute the inflaton scalar potential and investigate the possibility of inflation. We confirm the existence of slow-roll inflation with an exit. However, the model suffers from the η-problem that gives rise to the unacceptable value of the spectral index ns of scalar perturbations.