Showing papers on "Scalar potential published in 2011"
TL;DR: In this article, a basis-independent expression for the constraints that impose custodial symmetry on the 2Higgs scalar potential was obtained, and the mass degeneracies of the two-Higgs doublet model were clarified.
Abstract: In the Standard Model, custodial symmetry is violated by the hypercharge U(1) gauge interactions and the Yukawa couplings, while being preserved by the Higgs scalar potential. In the two-Higgs doublet model (2HDM), the generic scalar potential introduces new sources of custodial symmetry breaking. We obtain a basis-independent expression for the constraints that impose custodial symmetry on the 2HDM scalar potential. These constraints impose CP-conservation on the scalar potential and vacuum, and in addition add one extra constraint on the scalar potential parameters. We clarify the mass degeneracies of the 2HDM that arise as a consequence of the custodial symmetry. We also provide a computation of the 'oblique' parameters (S, T, and U) for the most general CP-violating 2HDM in the basis-independent formalism. We demonstrate that the 2HDM contributions to T and U vanish in the custodial symmetry limit, as expected. Using the experimental bounds on S and T from precision electroweak data, we examine the resulting constraints on the general 2HDM parameter space.
294 citations
TL;DR: In this article, the NSNS Lagrangian of ten-dimensional supergravity is rewritten via a change of field variables inspired by Generalized Complex Geometry, and a new metric and dilaton are obtained, together with an anti-symmetric bivector field which leads to a 10-dimensional version of the non-geometric Q-flux.
Abstract: The NSNS Lagrangian of ten-dimensional supergravity is rewritten via a change of field variables inspired by Generalized Complex Geometry. We obtain a new metric and dilaton, together with an anti symmetric bivector field which leads to a ten-dimensional version of the non-geometric Q-flux. Given the involved global aspects of non-geometric situations, we prescribe to use this new Lagrangian, whose associated action is well-defined in some examples investigated here. This allows us to perform a standard dimensional reduction and to recover the usual contribution of the Q-flux to the four-dimensional scalar potential. An extension of this work to include the R-flux is discussed. The paper also contains a brief review on non-geometry.
218 citations
Book•
16 Jul 2011
TL;DR: In this paper, a generalized hypervirial theorem for Schroedinger equation with Coulomb potential was proposed for the special orthogonal groups (SO(n) with position-dependent mass.
Abstract: Part I (Introduction).- Part II (Theory). - 2. Special orthogonal groups (Introduction Abstract groups Orthogonal group SO(n) Tensor representations of the SO(n) \Gamma matrix groups Spinor representations of the SO(n) Concluding remarks).- 3. Rotational symmetry and Schroedinger equation in N-dimensional space (Introduction Rotation operator Orbital angular momentum operators The linear momentum operators Radial momentum operator Spherical harmonic polynomials Schroedinger equation for a two-body system Concluding remarks).- 4. Dirac equation in higher dimensions (Introduction Dirac equation in N+1 dimensions The radial equation Application to hydrogen atom Concluding remarks).- 5. Klein-Gordon equation in higher dimensions (Introduction The Radial equation Application to hydrogen atom Concluding remarks).- Part III (Application in Non-relativistic Quantum Mechanics).- 6. Harmonic oscillator (Introduction Exact solutions of harmonic oscillator Recurrence relations for the radioal function Realization of dynamic group SU(1, 1) Generalization to pseudoharmonic ooscillator Position and momentum information entropy Conclusions).- 7. Coulomb potential (Introduction Exact solution Shift operators Mapping between Coulumb and harmonic oscillator radial functions Realization of dynamic of dynamic group SU (1, 1) Generalization to Kratzer potential Concluding remarks).- 8. Wave function ansatz method (Introduction Sextic potential Singular one-fraction power potential Mixture potential Non-polynomial potential Screened Coulomb potential Morse potential Conclusions).- 9. Levinson theorem for Schroedinger equation (Introduction Scattering states and phase shifts Bound states Sturm--Liouville theorem Levinson theorem Discussions Conclusions).- 10. Generalized hypervirial theorem for Schroedinger equation (Introduction Generalized Blanchard's and Kramers' recurrence relations Applications to central potentials Conclusions).- 11. Exact quantization rule and Langer modification (Introduction WKB approximation Exact quantization rule Application to trigonometric Rosen-Morse potential Proper quantization rule Illustrations of proper quantization rule Langer modification in D dimensions Calculations of logarithmic derivatives of wavefunction Conclusions).- 12. Schroedinger equation with position-dependent mass (Introduction Formalism Applications to harmonic oscillator and Coulomb potential Conclusions).- Part IV (Application in Relativistic Quantum Mechanics).- 13. Dirac equation with Coulomb potential (Introduction Exact solutions of hydrogen-like atoms Analysis of eigenvalues Generalization to the Dirac equation with Coulomb potential plus scalar potential Concluding remarks).- 14. Klein-Gordon equation with Coulomb potential (Introduction Eigenfunctions and eigenvalues Analysis of eigenvalues Generalization: Klein-Gordon equation with Coulomb plus scalar potential Comparison theorem Conclusions).- 15. Levinson theorem for Dirac equation (Introduction Generalization Sturm-Liouville theorem Number of bound states Relativistic Levinson theorem Discussions Friedel Theorem Comparison theorem Conclusions).- 16. Generalized hypervirial theorem for Dirac equation (Introduction Relativistic recurrence relation Diagonal case Conclusions).- 17. Kaluza-Klein theory (Introduction (4+D) -dimensional Kaluza-Klein theories Paritcle spectrum of Kaluza-Klein theories for ferminions Warped extra dimensions Conclusions).- PART V (Conclusions and Outlooks).- 18. Conclusions and outlooks.- Appendices.- References.- Index.
174 citations
TL;DR: In this article, theoretical and phenomenological aspects of two-Higgs-doublet extensions of the Standard Model are discussed, including the role of symmetries in the scalar sector.
Abstract: We discuss theoretical and phenomenological aspects of two-Higgs-doublet extensions of the Standard Model. In general, these extensions have scalar mediated flavour changing neutral currents which are strongly constrained by experiment. Various strategies are discussed to control these flavour changing scalar currents and their phenomenological consequences are analysed. In particular, scenarios with natural flavour conservation are investigated, including the so-called type I and type II models as well as lepton-specific and inert models. Type III models are then discussed, where scalar flavour changing neutral currents are present at tree level, but are suppressed by either specific ansatze for the Yukawa couplings or by the introduction of family symmetries. We also consider the phenomenology of charged scalars in these models. Next we turn to the role of symmetries in the scalar sector. We discuss the six symmetry-constrained scalar potentials and their extension into the fermion sector. The vacuum structure of the scalar potential is analysed, including a study of the vacuum stability conditions on the potential and its renormalization-group improvement. The stability of the tree level minimum of the scalar potential in connection with electric charge conservation and its behaviour under CP is analysed. The question of CP violation is addressed in detail, including the cases of explicit CP violation and spontaneous CP violation. We present a detailed study of weak basis invariants which are odd under CP. A careful study of spontaneous CP violation is presented, including an analysis of the conditions which have to be satisfied in order for a vacuum to violate CP. We present minimal models of CP violation where the vacuum phase is sufficient to generate a complex CKM matrix, which is at present a requirement for any realistic model of spontaneous CP violation.
164 citations
TL;DR: In this article, the general conditions of convexity and stability of the scalar potential of the two-Higgs doublet model were derived and the topological defects associated with spontaneous symmetry breaking of each symmetry were identified.
Abstract: We perform a systematic study of generic accidental Higgs-family and CP symmetries that could occur in the two-Higgs-doublet-model potential, based on a Majorana scalar-field formalism which realizes a subgroup of \( {\text{GL}}\left( {8,\mathbb{C}} \right) \). We derive the general conditions of convexity and stability of the scalar potential and present analytical solutions for two non-zero neutral vacuum expectation values of the Higgs doublets for a typical set of six symmetries, in terms of the gauge-invariant parameters of the theory. By means of a homotopy-group analysis, we identify the topological defects associated with the spontaneous symmetry breaking of each symmetry, as well as the massless Goldstone bosons emerging from the breaking of the continuous symmetries. We find the existence of domain walls from the breaking of Z2, CP1 and CP2 discrete symmetries, vortices in models with broken U(1)PQ and CP3 symmetries and a global monopole in the SO(3)HF-broken model. The spatial profile of the topological defect solutions is studied in detail, as functions of the potential parameters of the two-Higgs doublet model. The application of our Majorana scalar-field formalism in studying more general scalar potentials that are not constrained by the U(1)Y hypercharge symmetry is discussed. In particular, the same formalism may be used to properly identify seven additional symmetries that may take place in a U(1)Y-invariant scalar potential.
111 citations
TL;DR: In this article, the authors study the six-field dynamics of D3-brane inflation for a general scalar potential on the conifold, finding simple, universal behavior.
Abstract: We study the six-field dynamics of D3-brane inflation for a general scalar potential on the conifold, finding simple, universal behavior. We numerically evolve the equations of motion for an ensemble of more than 7107 realizations, drawing the coefficients in the scalar potential from statistical distributions whose detailed properties have demonstrably small effects on our results. When prolonged inflation occurs, it has a characteristic form: the D3-brane initially moves rapidly in the angular directions, spirals down to an inflection point in the potential, and settles into single-field inflation. The probability of Ne e-folds of inflation is a power law, P(Ne)∝Ne−3, and we derive the same exponent from a simple analytical model. The success of inflation is relatively insensitive to the initial position: we find attractor behavior in the angular directions, and the D3-brane can begin far above the inflection point without overshooting. Initial radial or angular velocities, on the other hand, can have a significant effect on the duration of inflation. In favorable regions of the spaces of initial velocities and of Lagrangian parameters, models yielding 60 e-folds of expansion arise approximately once in 103 trials. Realizations that are effectively single-field and give rise to a primordial spectrum of fluctuations consistent with WMAP, for which at least 120 e-folds are required, arise approximately once in 105 trials. The emergence of robust predictions from a six-field potential with hundreds of terms invites an analytic approach to multifield inflation.
108 citations
TL;DR: In this article, the authors investigated a class of near-extremal solutions of the Einstein-Maxwell scalar theory with electric charge and power law scaling, dual to charged IR phases of relativistic field theories at low temperature.
Abstract: We investigate a class of near-extremal solutions of Einstein-Maxwell-scalar theory with electric charge and power law scaling, dual to charged IR phases of relativistic field theories at low temperature. These are exact solutions of theories with domain wall vacua; hence, we use nonconformal holography to relate the bulk and boundary theories. We numerically construct a global interpolating solution between the IR charged solutions and the UV domain wall vacua for arbitrary physical choices of Lagrangian parameters. By passing to a conformal frame in which the domain wall metric becomes that of AdS, we uncover a generalized scale invariance of the IR scaling solution, indicating a connection to the physics of Lifshitz fixed points. Finally, guided by effective field theoretic principles and the physics of nonconformal D-branes, we argue for the applicability of domain wall holography even in theories with AdS critical points, namely those theories for which a scalar potential is dominated by a single exponential term over a large range.
102 citations
TL;DR: In this article, the authors consider a dynamical system moving in a Riemannian space and prove two theorems which relate the Lie point symmetries and Noether symmets of the equation of motion, with the special projective group and the homothetic group of the space respectively.
Abstract: We consider a dynamical system moving in a Riemannian space and prove two theorems which relate the Lie point symmetries and Noether symmetries of the equation of motion, with the special projective group and the homothetic group of the space respectively. These theorems are used to classify the two-dimensional Newtonian dynamical systems, which admit Lie point/Noether symmetries. The results of the study, i.e. expressions of forces/potentials, Lie symmetries, Noether vectors and Noether integrals are presented in the form of tables for easy reference and convenience. Two cases are considered, Hamiltonian and non-Hamiltonian systems. The results are used to determine the Lie/Noether symmetries of two different systems. The Kepler–Ermakov system, which in general is non-conservative, and the conservative system with potential similar to the Henon–Heiles potential. As an additional application, we consider the scalar field cosmologies in a FRW background with no matter, and look for the scalar field potentials for which the resulting cosmological models are integrable. It is found that the only integrable scalar field cosmologies are defined by the exponential and the unified dark matter potential. It is to be noted that in all aforementioned applications the Lie/Noether symmetry vectors are found by simply reading the appropriate entry in the relevant tables.
84 citations
TL;DR: In this article, the authors studied the six-field dynamics of D3-brane inflation for a general scalar potential on the conifold, finding simple, universal behavior.
Abstract: We study the six-field dynamics of D3-brane inflation for a general scalar potential on the conifold, finding simple, universal behavior. We numerically evolve the equations of motion for an ensemble of more than 7 \times 10^7 realizations, drawing the coefficients in the scalar potential from statistical distributions whose detailed properties have demonstrably small effects on our results. When prolonged inflation occurs, it has a characteristic form: the D3-brane initially moves rapidly in the angular directions, spirals down to an inflection point in the potential, and settles into single-field inflation. The probability of N_{e} e-folds of inflation is a power law, P(N_{e}) \propto N_{e}^{-3}, and we derive the same exponent from a simple analytical model. The success of inflation is relatively insensitive to the initial conditions: we find attractor behavior in the angular directions, and the D3-brane can begin far above the inflection point without overshooting. In favorable regions of the parameter space, models yielding 60 e-folds of expansion arise approximately once in 10^3 trials. Realizations that are effectively single-field and give rise to a primordial spectrum of fluctuations consistent with WMAP, for which at least 120 e-folds are required, arise approximately once in 10^5 trials. The emergence of robust predictions from a six-field potential with hundreds of terms invites an analytic approach to multifield inflation.
74 citations
TL;DR: In this article, the authors derived the general scalar potential for fields whose background values are the Yukawa couplings, and analyzed the minimum of the potential and discussed the fine-tuning required to dynamically generate the mass hierarchies and the mixings between different quark generations.
Abstract: Assuming the Minimal Flavour Violation hypothesis, we derive the general scalar potential for fields whose background values are the Yukawa couplings. We analyze the minimum of the potential and discuss the fine-tuning required to dynamically generate the mass hierarchies and the mixings between different quark generations. Two main cases are considered, corresponding to Yukawa interactions being effective operators of dimension five or six (or, equivalently, resulting from bi-fundamental and fundamental scalar fields, respectively). At the renormalizable and classical level, no mixing is naturally induced from dimension five Yukawa operators. On the contrary, from dimension six Yukawa operators one mixing angle and a strong mass hierarchy among the generations result.
71 citations
TL;DR: In this article, the general solution for a scalar field cosmology with an exponential potential was studied, correcting some imprecisions, encountered previously in the literature, and the solution was generalized to a piecewise exponential potential, which is continuous but not smooth.
Abstract: We study in detail the general solution for a scalar field cosmology with an exponential potential, correcting some imprecisions, encountered previously in the literature. In addition, we generalize this solution for a piecewise exponential potential, which is continuous, but not smooth (with cusps).
TL;DR: In this paper, the authors use a Kaluza-Klein reduction to compute the low energy effective action for the massless modes of a spacetime-filling D6-brane wrapped on a special Lagrangian 3-cycle of a type IIA Calabi-Yau orientifold.
Abstract: We use a Kaluza-Klein reduction to compute the low-energy effective action for the massless modes of a spacetime-filling D6-brane wrapped on a special Lagrangian 3-cycle of a type IIA Calabi-Yau orientifold. The modifications to the characteristic data of the N=1 bulk orientifold theory in the presence of a D6-brane are analysed by studying the underlying Type IIA supergravity coupled to the brane worldvolume in the democratic formulation and performing a detailed dualisation procedure. The N=1 chiral coordinates are found to be in agreement with expectations from mirror symmetry. We work out the Kahler potential for the chiral superfields as well as the gauge kinetic functions for the bulk and the brane gauge multiplets including the kinetic mixing between the two. The scalar potential resulting from the dualisation procedure can be formally interpreted in terms of a superpotential. Finally, the gauging of the Peccei-Quinn shift symmetries of the complex structure multiplets reproduces the D-term potential enforcing the calibration condition for special Lagrangian 3-cycles.
TL;DR: In this article, the authors derived the general scalar potential for fields whose background values are the Yukawa couplings, and analyzed the minimum of the potential and discussed the fine-tuning required to dynamically generate the mass hierarchies and the mixings between different quark generations.
Abstract: Assuming the Minimal Flavour Violation hypothesis, we derive the general scalar potential for fields whose background values are the Yukawa couplings. We analyze the minimum of the potential and discuss the fine-tuning required to dynamically generate the mass hierarchies and the mixings between different quark generations. Two main cases are considered, corresponding to Yukawa interactions being effective operators of dimension five or six (or, equivalently, resulting from bi-fundamental and fundamental scalar fields, respectively). At the renormalizable and classical level, no mixing is naturally induced from dimension five Yukawa operators. On the contrary, from dimension six Yukawa operators one mixing angle and a strong mass hierarchy among the generations result.
TL;DR: In this paper, topological BPS solutions of an Abelian Maxwell-Higgs theory endowed by non-standard kinetic terms to both gauge and scalar fields are studied. And the numerical results present interesting new features, and contribute to the development of the recent issue concerning the study of generalized models and their applications.
Abstract: We look for topological BPS solutions of an Abelian Maxwell–Higgs theory endowed by non-standard kinetic terms to both gauge and scalar fields. Here, the non-usual dynamics are controlled by two positive functions, G(|ϕ|) and w(|ϕ|), which are related to the self-dual scalar potential V(|ϕ|) of the model by a fundamental constraint. The numerical results we found present interesting new features, and contribute to the development of the recent issue concerning the study of generalized models and their applications.
TL;DR: In this paper, the back-reaction of pairs of codimension-two branes within an explicit flux-stabilized compactification is studied, and the scalar potential and changes to the extra-dimensional and on-brane geometries that result, as functions of the assumed brane couplings.
Abstract: We compute the back-reaction of pairs of codimension-two branes within an explicit flux-stabilized compactification, to trace how its properties depend on the parameters that define the brane-bulk couplings. Both brane tension and magnetic couplings to the stabilizing flux play an important role in the resulting dynamics, with the magnetic coupling allowing some of the flux to be localized on the branes (thus changing the flux-quantization conditions). We find that back-reaction lifts the classical flat directions of the bulk supergravity, and we calculate both the scalar potential and changes to the extra-dimensional and on-brane geometries that result, as functions of the assumed brane couplings. When linearized about simple rugby-ball geometries the resulting solutions allow a systematic exploration of the system’s response. Several of the systems we explore have remarkable properties. Among these are a propensity for the extra dimensions to stabilize at exponentially large sizes, providing a mechanism for generating extremely large volumes. In some circumstances the brane-dilaton coupling allows the bulk dilaton to adjust to suppress the on-brane curvature parametrically below the change in brane tension, potentially providing a mechanism for reducing the vacuum energy. We explore the stability of this suppression to quantum effects in the case where their strength is controlled by the value of the field along the classical flat direction, and find it can (but need not) be stable.
TL;DR: In this paper, a method for analyzing the magnetic field and predicting the cogging force and torque of a linear and rotary permanent magnet actuator (LRPMA) is presented.
Abstract: This paper presents a method for analytically analyzing the magnetic field and predicting the cogging force and torque of a linear and rotary permanent magnet actuator (LRPMA). The tubular mover of the LRPMA is transferred into a planar one by using a proposed magnetic field curvature factor and a relative permeance function for the stator slotting so as to simplify the magnetic field calculation. Magnetic field distributions of the LRPMA when the stator slotting is neglected are analytically analyzed using the magnetic scalar potential, and validated by 3-D finite-element method. The linear cogging force and rotary cogging torque of slotted LRPMA are subsequently predicted by the Maxwell stress tensor method and verified by the experimental results on the prototype.
TL;DR: In this paper, the NSNS Lagrangian of ten-dimensional supergravity is rewritten via a change of field variables inspired by Generalized Complex Geometry, and a new metric and dilaton are obtained, together with an antisymmetric bivector field which leads to a tendimensional version of the non-geometric Q-flux.
Abstract: The NSNS Lagrangian of ten-dimensional supergravity is rewritten via a change of field variables inspired by Generalized Complex Geometry. We obtain a new metric and dilaton, together with an antisymmetric bivector field which leads to a ten-dimensional version of the non-geometric Q-flux. Given the involved global aspects of non-geometric situations, we prescribe to use this new Lagrangian, whose associated action is well-defined in some examples investigated here. This allows us to perform a standard dimensional reduction and to recover the usual contribution of the Q-flux to the four-dimensional scalar potential. An extension of this work to include the R-flux is discussed. The paper also contains a brief review on non-geometry.
TL;DR: In this paper, a generalized Bianchi type I anisotropic cosmology in 5D Brans-Dicke theory is investigated, and the induced scalar potential is found to be in the power law or in the logarithmic form.
Abstract: Recently, it has been shown that a four-dimensional (4D) Brans–Dicke (BD) theory with an effective matter field and a self-interacting potential can be achieved from the vacuum 5D BD field equations, where we refer to as a modified Brans–Dicke theory (MBDT). We investigate a generalized Bianchi type I anisotropic cosmology in 5D BD theory, and by employing the obtained formalism, we derive the induced matter on any 4D hypersurface in the context of the MBDT. We illustrate that if the usual spatial scale factors are functions of the time while the scale factor of extra dimension is constant, and the scalar field depends on the time and the fifth coordinate, then, in general, one will encounter inconsistencies in the field equations. Then, we assume that the scale factors and the scalar field depend on the time and the extra coordinate as separated variables in the power-law forms. Hence, we find a few classes of solutions in 5D spacetime through which we probe the one which leads to a generalized Kasner relation among the Kasner parameters. The induced scalar potential is found to be in the power law or in the logarithmic form; however, for a constant scalar field and even when the scalar field only depends on the fifth coordinate, it vanishes. The conservation law is indeed valid in this MBDT approach for the derived induced energy–momentum tensor (EMT). We proceed our investigations for a few cosmological quantities, where for simplicity we assume that the metric and the scalar field are functions of the time. Hence, the EMT satisfies the barotropic equation of state, and the model indicates that the constant mean Hubble parameter is not allowed. Thus, by appealing to the variation of the Hubble parameter, we assume a fixed deceleration parameter, and set the evolution of the quantities with respect to the fixed deceleration, the BD coupling and the state parameters. The WEC allows a shrinking extra dimension for a decelerating expanding universe that, in the constant scalar field, evolves the same way as the flat FRW spacetime in GR. The quantities for the stiff fluid and the radiation-dominated universe indicate an expanding universe commenced with a big bang. There is a horizon for each of the fluids, and the rate of expansion slows down by the time. The allowed ranges of the deceleration and the BD coupling parameters have been obtained, and the model gives an empty universe when the time goes to infinity.
TL;DR: In this paper, the scaling laws of thermodynamic functions, as well as the viscosity coefficients near the transition were obtained in the singular limit where the black-hole horizon marginally traps a curvature singularity.
Abstract: We investigate continuous Hawking-Page transitions in Einstein’s gravity coupled to a scalar field with an arbitrary potential in the weak gravity limit. We show that this is only possible in a singular limit where the black-hole horizon marginally traps a curvature singularity. Depending on the subleading terms in the potential, a rich variety of continuous phase transitions arise. Our examples include second and higher order, including the Berezinskii-Kosterlitz-Thouless type. In the case when the scalar is dilaton, the condition for continuous phase transitions lead to (asymptotically) linear-dilaton background. We obtain the scaling laws of thermodynamic functions, as well as the viscosity coefficients near the transition. In the limit of weak gravitational interactions, the bulk viscosity asymptotes to a universal constant, independent of the details of the scalar potential. As a byproduct of our analysis we obtain a one-parameter family of kink solutions in arbitrary dimension d that interpolate between AdS near the boundary and linear-dilaton background in the deep interior. The continuous Hawking-Page transitions found here serve as holographic models for normal-to superfluid transitions.
TL;DR: In this article, the most general first-order symmetry operator for the Dirac equation coupled to arbitrary fluxes is derived in terms of an inhomogeneous form ω, which is a solution to a coupled system of firstorder partial differential equations which is called the generalized conformal Killing-Yano system.
TL;DR: In this article, it was shown that the late time acceleration is driven by the effective cosmological constant rather than the Gauss-Bonnet term, which is a plausible answer to the well-known coincidence problem, and that the symmetry with the same form of the potential and coupling parameter exists all in the vacuum, radiation and matter dominated era.
Abstract: Noether symmetry for Gauss–Bonnet Dilatonic interaction exists for a constant dilatonic scalar potential and a linear functional dependence of the coupling parameter on the scalar field. The symmetry with the same form of the potential and coupling parameter exists all in the vacuum, radiation and matter dominated era. The late time acceleration is driven by the effective cosmological constant rather than the Gauss–Bonnet term, while the later compensates for the large value of the effective cosmological constant giving a plausible answer to the well-known coincidence problem.
TL;DR: In this article, a Preisach model has been used to simulate the vector hysteresis properties of ferromagnetic materials using a single sheet tester with a disk-shaped specimen at low frequency.
Abstract: The paper presents a Preisach model to simulate the vector hysteresis properties of ferromagnetic materials. The vector behavior has been studied using a single sheet tester with a disk-shaped specimen at low frequency. The locus of the magnetic flux density vector has been controlled by a digital measurement system. An inverse vector Preisach hysteresis model has been developed and identified by applying the measured data. Finally, the inverse model has been inserted into a finite element procedure through the fixed point technique and the reduced magnetic scalar potential formulation to simulate the measurement system. The applicability of the measurement system as well as the developed model has been proven by comparing measured and simulated results.
TL;DR: In this paper, a modified Brans-Dicke theory with effective matter field and self interacting potential can be achieved from vacuum 5D BD field equations, where they refer to as modified MBDT, and derive induced-matter on any 4D hypersurface in context of the MBDT.
Abstract: It has been shown that four dimensional Brans-Dicke theory with effective matter field and self interacting potential can be achieved from vacuum 5D BD field equations, where we refer to as modified Brans-Dicke theory (MBDT). We investigate a generalized Bianchi type I anisotropic cosmology in 5D BD theory, and by employing obtained formalism, we derive induced-matter on any 4D hypersurface in context of the MBDT. We illustrate that if the usual spatial scale factors are functions of time while scale factor of extra dimension is constant, and scalar field depends on time and fifth coordinate, then in general, one will encounter inconsistencies in field equations. Then, we assume the scale factors and scalar field depend on time and extra coordinate as separated variables in power law forms. Hence, we find a few classes of solutions in 5D spacetime through which, we probe the one which leads to a generalized Kasner relations among Kasner parameters. The induced scalar potential is found to be in power law or in logarithmic form, however, for constant scaler field and even when scalar field only depends on fifth coordinate, it vanishes. The conservation law is indeed valid in this MBDT approach for derived induced energy momentum tensor (EMT). We proceed our investigations for a few cosmological quantities, where for simplicity we assume metric and scalar field are functions of time. Hence, the EMT satisfies barotropic equation of state, and the model indicates that constant mean Hubble parameter is not allowed. Thus, by appealing to variation of Hubble parameter, we assume a fixed deceleration parameter, and set evolution of quantities with respect to the fixed deceleration, BD coupling and state parameters. The WEC allows a shrinking extra dimension for decelerating expanding universe that, in the constant scalar field, evolves same as flat FRW spacetime in GR.
TL;DR: In this paper, it was shown that when the inflaton field modulates the gauge kinetic function of the gauge fields in supergravity realisations of inflation, the dynamic backreaction leads to a new inflationary attractor solution, in which the inflation's variation suffers additional impedance.
Abstract: It is shown that, when the inflaton field modulates the gauge kinetic function of the gauge fields in supergravity realisations of inflation, the dynamic backreaction leads to a new inflationary attractor solution, in which the inflaton's variation suffers additional impedance. As a result, slow-roll inflation can naturally occur along directions of the scalar potential which would be too steep and curved to support it otherwise. This provides a generic solution to the infamous eta-problem of inflation in supergravity. Moreover, it is shown that, in the new inflationary attractor, the spectral index of the generated curvature perturbations is kept mildly red despite eta of order unity. The above findings are applied to a model of hybrid inflation is supergravity with a generic Kaehler potential. The spectral index of the generated curvature perturbations is found to be 0.97 - 0.98, in excellent agreement with observations. The gauge field can play the role of the vector curvaton after inflation but observable statistical anisotropy requires substantial tuning of the gauge coupling.
TL;DR: In this article, it was shown that the symmetry for Gauss-Bonnet-Dilatonic interaction for a constant dilatonic scalar potential and a linear functional dependence of the coupling parameter on the scalar field exists all in the vacuum, radiation and matter dominated era.
Abstract: Noether symmetry for Gauss-Bonnet-Dilatonic interaction exists for a constant dilatonic scalar potential and a linear functional dependence of the coupling parameter on the scalar field. The symmetry with the same form of the potential and coupling parameter exists all in the vacuum, radiation and matter dominated era. The late time acceleration is driven by the effective cos- mological constant rather than the Gauss-Bonnet term, while the later compensates for the large value of the effective cosmological constant giving a plausible answer to the well-known coincidence problem.
TL;DR: In this article, the Nicolai mapping is applied to a SUSY matrix model with a double-well scalar potential, which is similar to the one in this paper.
TL;DR: In this paper, the Dirac equation in 1+1 space-time dimension with vector, scalar and pseudo-scalar coupling was considered, and a model with significant extensions to supersymmetric quantum mechanics was proposed.
TL;DR: In this paper, exact analytic solutions for a class of scalar-tensor gravity theories with a hyperbolic scalar potential are presented, which can be used to solve more complicated theories with more scalar fields.
Abstract: Exact analytic solutions for a class of scalar-tensor gravity theories with a hyperbolic scalar potential are presented. Using an exact solution we have successfully constructed a model of inflation that produces the spectral index, the running of the spectral index, and the amplitude of scalar perturbations within the constraints given by the WMAP 7 years data. The model simultaneously describes the big bang and inflation connected by a specific time delay between them so that these two events are regarded as dependent on each other. In solving the Friedmann equations, we have utilized an essential Weyl symmetry of our theory in 3+1 dimensions which is a predicted remaining symmetry of 2T-physics field theory in 4+2 dimensions. This led to a new method of obtaining analytic solutions in the 1T field theory which could in principle be used to solve more complicated theories with more scalar fields. Some additional distinguishing properties of the solution includes the fact that there are early periods of time when the slow-roll approximation is not valid. Furthermore, the inflaton does not decrease monotonically with time; rather, it oscillates around the potential minimum while settling down, unlike the slow-roll approximation. While the model we used for illustrationmore » purposes is realistic in most respects, it lacks a mechanism for stopping inflation. The technique of obtaining analytic solutions opens a new window for studying inflation, and other applications, more precisely than using approximations.« less
TL;DR: In this paper, a scalar field with potential wells and other degrees of freedom interacting with it can localize this field by decoherence in one of the wells, which can then acquire a small positive value.
Abstract: We address the issue why a cosmological constant (dark energy) possesses a small positive value instead of being zero. Motivated by the cosmic landscape picture, we mimic the dark energy by a scalar field with potential wells and show that other degrees of freedom interacting with it can localize this field by decoherence in one of the wells. Dark energy can then acquire a small positive value. We also show that the additional degrees of freedom enhance the tunneling rate between the wells. The consideration is performed in detail for the case of two wells and then extended to a large number of wells.
TL;DR: In this article, a self-adjoint radial Dirac Hamiltonian with a Coulomb scalar potential and an Aharonov-Bohm potential in 2+1 dimensions was constructed by taking into account a fermion spin.
Abstract: The quantum-mechanical problem of constructing the self-adjoint Hamiltonians is physically rigorously solved for a Dirac Hamiltonian with a Coulomb scalar potential and an Aharonov–Bohm potential in 2+1 dimensions by taking into account a fermion spin. It is found that the Dirac Hamiltonian on this background requires the additional specification of a one-parameter self-adjoint extension, which can be given in terms of the physically acceptable boundary conditions. We derive equations that determine the spectra of the self-adjoint radial Dirac Hamiltonians for various parameter values. We discuss the role of a particle spin as the physical reason of the existence of bound fermion states in a pure Aharonov–Bohm potential and show that the particle and antiparticle states with zero energy exist only owing to the interaction of the fermion spin magnetic moment with the magnetic field. The energy levels of particles and antiparticles are intersected what may signal on the instability of a quantum system.