Posts Tagged scalar field

Recent Postings from scalar field

Higgsophilic gauge bosons and monojets at the LHC

We consider a generic framework where the Standard Model (SM) coexists with a hidden sector endowed with some additional gauge symmetry. When this symmetry is broken by a scalar field charged under the hidden gauge group, the corresponding scalar boson generally mixes with the SM Higgs boson. In addition, massive hidden gauge bosons emerge and via the mixing, the observed Higgs-like mass eigenstate is the only known particle that couples to these hidden gauge bosons directly. We study the LHC monojet signatures of this scenario and the corresponding constraints on the gauge coupling of the hidden gauge group as well as the mixing of the Higgs scalars.

Encyclopaedia Curvatonis

We investigate whether the predictions of single-field models of inflation are robust under the introduction of additional scalar degrees of freedom, and whether these extra fields change the potentials for which the data show the strongest preference. We study the situation where an extra light scalar field contributes both to the total curvature perturbations and to the reheating kinematic properties. Ten reheating scenarios are identified, and all necessary formulas allowing a systematic computation of the predictions for this class of models are derived. They are implemented in the public library ASPIC, which contains more than 75 single-field potentials. This paves the way for a forthcoming full Bayesian analysis of the problem. A few representative examples are displayed and discussed.

Encyclopaedia Curvatonis [Cross-Listing]

We investigate whether the predictions of single-field models of inflation are robust under the introduction of additional scalar degrees of freedom, and whether these extra fields change the potentials for which the data show the strongest preference. We study the situation where an extra light scalar field contributes both to the total curvature perturbations and to the reheating kinematic properties. Ten reheating scenarios are identified, and all necessary formulas allowing a systematic computation of the predictions for this class of models are derived. They are implemented in the public library ASPIC, which contains more than 75 single-field potentials. This paves the way for a forthcoming full Bayesian analysis of the problem. A few representative examples are displayed and discussed.

Encyclopaedia Curvatonis [Cross-Listing]

We investigate whether the predictions of single-field models of inflation are robust under the introduction of additional scalar degrees of freedom, and whether these extra fields change the potentials for which the data show the strongest preference. We study the situation where an extra light scalar field contributes both to the total curvature perturbations and to the reheating kinematic properties. Ten reheating scenarios are identified, and all necessary formulas allowing a systematic computation of the predictions for this class of models are derived. They are implemented in the public library ASPIC, which contains more than 75 single-field potentials. This paves the way for a forthcoming full Bayesian analysis of the problem. A few representative examples are displayed and discussed.

Encyclopaedia Curvatonis [Cross-Listing]

We investigate whether the predictions of single-field models of inflation are robust under the introduction of additional scalar degrees of freedom, and whether these extra fields change the potentials for which the data show the strongest preference. We study the situation where an extra light scalar field contributes both to the total curvature perturbations and to the reheating kinematic properties. Ten reheating scenarios are identified, and all necessary formulas allowing a systematic computation of the predictions for this class of models are derived. They are implemented in the public library ASPIC, which contains more than 75 single-field potentials. This paves the way for a forthcoming full Bayesian analysis of the problem. A few representative examples are displayed and discussed.

Local energy-momentum conservation in scalar-tensor-like gravity with generic curvature invariants [Cross-Listing]

For a large class of scalar-tensor-like modified gravity whose action contains nonminimal couplings between a scalar field $\phi(x^\alpha)$ and generic curvature invariants $\mathcal{R}$ beyond the Ricci scalar $R=R^\alpha_{\;\;\alpha}$, we prove the covariant invariance of its field equation and confirm/prove the local energy-momentum conservation. These $\phi(x^\alpha)-\mathcal{R}$ coupling terms break the symmetry of diffeomorphism invariance under a particle transformation, which implies that the solutions of the field equation should satisfy the consistency condition $\mathcal{R}\equiv 0$ when $\phi(x^\alpha)$ is nondynamical and massless. Following this fact and based on the accelerated expansion of the observable Universe, we propose a primary test to check the viability of the modified gravity to be an effective dark energy, and a simplest example passing the test is the "Weyl/conformal dark energy".

Local energy-momentum conservation in scalar-tensor-like gravity with generic curvature invariants

For a large class of scalar-tensor-like modified gravity whose action contains nonminimal couplings between a scalar field $\phi(x^\alpha)$ and generic curvature invariants $\mathcal{R}$ beyond the Ricci scalar $R=R^\alpha_{\;\;\alpha}$, we prove the covariant invariance of its field equation and confirm/prove the local energy-momentum conservation. These $\phi(x^\alpha)-\mathcal{R}$ coupling terms break the symmetry of diffeomorphism invariance under a particle transformation, which implies that the solutions of the field equation should satisfy the consistency condition $\mathcal{R}\equiv 0$ when $\phi(x^\alpha)$ is nondynamical and massless. Following this fact and based on the accelerated expansion of the observable Universe, we propose a primary test to check the viability of the modified gravity to be an effective dark energy, and a simplest example passing the test is the "Weyl/conformal dark energy".

Local energy-momentum conservation in scalar-tensor-like gravity with generic curvature invariants [Cross-Listing]

For a large class of scalar-tensor-like modified gravity whose action contains nonminimal couplings between a scalar field $\phi(x^\alpha)$ and generic curvature invariants $\mathcal{R}$ beyond the Ricci scalar $R=R^\alpha_{\;\;\alpha}$, we prove the covariant invariance of its field equation and confirm/prove the local energy-momentum conservation. These $\phi(x^\alpha)-\mathcal{R}$ coupling terms break the symmetry of diffeomorphism invariance under a particle transformation, which implies that the solutions of the field equation should satisfy the consistency condition $\mathcal{R}\equiv 0$ when $\phi(x^\alpha)$ is nondynamical and massless. Following this fact and based on the accelerated expansion of the observable Universe, we propose a primary test to check the viability of the modified gravity to be an effective dark energy, and a simplest example passing the test is the "Weyl/conformal dark energy".

Hyperscaling violating black holes in scalar-torsion theories [Cross-Listing]

We study a gravity theory where a scalar field with potential, beyond its minimal coupling, is also coupled through a non-minimal derivative coupling with the torsion scalar which is the teleparallel equivalent of Einstein gravity. This theory provides second order equations of motion and we find large-distance non-perturbative static spherically symmetric four-dimensional solutions. Among them a general class of black hole solutions is found for some range of the parameters/integration constants with asymptotics of the form of hyperscaling violating Lifshitz spacetime with spherical horizon topology. Although the scalar field diverges at the horizon, its energy density and pressures are finite there. From the astrophysical point of view, this solution provides extra deflection of light compared to the Newtonian deflection.

Hyperscaling violating black holes in scalar-torsion theories

We study a gravity theory where a scalar field with potential, beyond its minimal coupling, is also coupled through a non-minimal derivative coupling with the torsion scalar which is the teleparallel equivalent of Einstein gravity. This theory provides second order equations of motion and we find large-distance non-perturbative static spherically symmetric four-dimensional solutions. Among them a general class of black hole solutions is found for some range of the parameters/integration constants with asymptotics of the form of hyperscaling violating Lifshitz spacetime with spherical horizon topology. Although the scalar field diverges at the horizon, its energy density and pressures are finite there. From the astrophysical point of view, this solution provides extra deflection of light compared to the Newtonian deflection.

Holographic metal/superconductor phase transitions with dark matter sector

In this paper, we investigate the holographic phase transitions with dark matter sector in the AdS black hole background away from the probe limit. We firstly detect the formation of the scalar hair by examining the behaviors of the superconducting solutions and the effective mass of the scalar field. Then we study the condensation of the scalar operator with respect to the Hawking temperature T. As a further step, we disclose the properties of the phase transitions from the holographic topological entanglement entropy of the system. The holographic topological entanglement entropy is proved to be very useful in characterizing the difference between various phases. At last, we also derive the qualitative properties through the analytical methods. In summary, we find that the model parameters can provide rich physics in the general holographic metal/superconductor phase transitions.

Hamiltonian description of the parametrized scalar field in bounded spatial regions

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.

Piercing the Vainshtein screen: Local constraints on modified gravity [Cross-Listing]

Modifications of gravity of the galileon type rely on the Vainshtein screening to pass solar system tests. Such a mechanism suppresses the fluctuations of the scalar field in the vicinity of localized sources, leaving the gravitons as the only mediators of gravitational interactions. We highlight that, in galileon 4 and 5 models and their shift-symmetric extensions, the inevitable presence of the scalar field gradient modifies the dynamics of the gravitons, leading to unscreened deviations from general relativity. The observational bounds on the gravitational slip parameter constrain the Horndeski-extensions of quartic and quintic galileons to the level of $10^{-5}$. The corresponding beyond-Horndeski models can also be constrained to the level of $10^{-2}$, by adding to the analysis the limits on the speed of gravitational waves coming from the observations of the orbital decay of the Hulse-Taylor pulsar.

Piercing the Vainshtein screen: Local constraints on modified gravity

Modifications of gravity of the galileon type rely on the Vainshtein screening to pass solar system tests. Such a mechanism suppresses the fluctuations of the scalar field in the vicinity of localized sources, leaving the gravitons as the only mediators of gravitational interactions. We highlight that, in galileon 4 and 5 models and their shift-symmetric extensions, the inevitable presence of the scalar field gradient modifies the dynamics of the gravitons, leading to unscreened deviations from general relativity. The observational bounds on the gravitational slip parameter constrain the Horndeski-extensions of quartic and quintic galileons to the level of $10^{-5}$. The corresponding beyond-Horndeski models can also be constrained to the level of $10^{-2}$, by adding to the analysis the limits on the speed of gravitational waves coming from the observations of the orbital decay of the Hulse-Taylor pulsar.

Piercing the Vainshtein screen: Local constraints on modified gravity [Cross-Listing]

Modifications of gravity of the galileon type rely on the Vainshtein screening to pass solar system tests. Such a mechanism suppresses the fluctuations of the scalar field in the vicinity of localized sources, leaving the gravitons as the only mediators of gravitational interactions. We highlight that, in galileon 4 and 5 models and their shift-symmetric extensions, the inevitable presence of the scalar field gradient modifies the dynamics of the gravitons, leading to unscreened deviations from general relativity. The observational bounds on the gravitational slip parameter constrain the Horndeski-extensions of quartic and quintic galileons to the level of $10^{-5}$. The corresponding beyond-Horndeski models can also be constrained to the level of $10^{-2}$, by adding to the analysis the limits on the speed of gravitational waves coming from the observations of the orbital decay of the Hulse-Taylor pulsar.

Decay of massive scalar field in a black hole background immersed in magnetic field

We calculated quasinormal modes of massive scalar field of the Ernst black holes, i.e., neutral black holes immersed in an external magnetic field. The Ernst solution reduces to the Schwarzschild solution when the magnetic field vanishes. It is found that the quasinormal spectrum for massive scalar field in the vicinity of the magnetized black holes acquires an effective mass $\mu_{eff}= \sqrt{4B^2 m^2+\mu^2}$, where $m$ is the azimuthal number, $\mu$ the mass of scalar field and $B$ the parameter describing the magnetic field. The numerical result shows that increasing of the field effective mass gives rise to decreasing of the imaginary part of the quasinormal modes until reaching the vanishing damping rate.

The Einstein-Klein-Gordon Equations, Wave Dark Matter, and the Tully-Fisher Relation

We examine the Einstein equation coupled to the Klein-Gordon equation for a complex-valued scalar field. These two equations together are known as the Einstein-Klein-Gordon system. In the low-field, non-relativistic limit, the Einstein-Klein-Gordon system reduces to the Poisson-Schr\"odinger system. We describe the simplest solutions of these systems in spherical symmetry, the spherically symmetric static states, and some scaling properties they obey. We also describe some approximate analytic solutions for these states. The EKG system underlies a theory of wave dark matter, also known as scalar field dark matter (SFDM), boson star dark matter, and Bose-Einstein condensate (BEC) dark matter. We discuss a possible connection between the theory of wave dark matter and the baryonic Tully-Fisher relation, which is a scaling relation observed to hold for disk galaxies in the universe across many decades in mass. We show how fixing boundary conditions at the edge of the spherically symmetric static states implies Tully-Fisher-like relations for the states. We also catalog other "scaling conditions" one can impose on the static states and show that they do not lead to Tully-Fisher-like relations–barring one exception which is already known and which has nothing to do with the specifics of wave dark matter.

The Einstein-Klein-Gordon Equations, Wave Dark Matter, and the Tully-Fisher Relation [Cross-Listing]

We examine the Einstein equation coupled to the Klein-Gordon equation for a complex-valued scalar field. These two equations together are known as the Einstein-Klein-Gordon system. In the low-field, non-relativistic limit, the Einstein-Klein-Gordon system reduces to the Poisson-Schr\"odinger system. We describe the simplest solutions of these systems in spherical symmetry, the spherically symmetric static states, and some scaling properties they obey. We also describe some approximate analytic solutions for these states. The EKG system underlies a theory of wave dark matter, also known as scalar field dark matter (SFDM), boson star dark matter, and Bose-Einstein condensate (BEC) dark matter. We discuss a possible connection between the theory of wave dark matter and the baryonic Tully-Fisher relation, which is a scaling relation observed to hold for disk galaxies in the universe across many decades in mass. We show how fixing boundary conditions at the edge of the spherically symmetric static states implies Tully-Fisher-like relations for the states. We also catalog other "scaling conditions" one can impose on the static states and show that they do not lead to Tully-Fisher-like relations–barring one exception which is already known and which has nothing to do with the specifics of wave dark matter.

Black hole solutions in Einstein-charged scalar field theory

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.

Black hole solutions in Einstein-charged scalar field theory [Cross-Listing]

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.

Generalised Smarr Formula and the Viscosity Bound for Einstein-Maxwell-Dilaton Black Holes [Replacement]

We study the shear viscosity to entropy ratio $\eta/S$ in the boundary field theories dual to black hole backgrounds in theories of gravity coupled to a scalar field, and generalisations including a Maxwell field and non-minimal scalar couplings. Motivated by the observation in simple examples that the saturation of the $\eta/S\ge 1/(4\pi)$ bound is correlated with the existence of a generalised Smarr relation for the planar black-hole solutions, we investigate this in detail for the general black-hole solutions in these theories, focusing especially on the cases where the scalar field plays a non-trivial role and gives rise to an additional parameter in the space of solutions. We find that a generalised Smarr relation holds in all cases, and in fact it can be viewed as the bulk gravity dual of the statement of the saturation of the viscosity to entropy bound. We obtain the generalised Smarr relation, whose existence depends upon a scaling symmetry of the planar black-hole solutions, by two different but related methods, one based on integrating the first law of thermodynamics, and the other based on the construction of a conserved Noether charge.

Generalised Smarr Formula and the Viscosity Bound for Einstein-Maxwell-Dilaton Black Holes

We study the shear viscosity to entropy ratio $\eta/S$ in the boundary field theories dual to black hole backgrounds in theories of gravity coupled to a scalar field, and generalisations including a Maxwell field and non-minimal scalar couplings. Motivated by the observation in simple examples that the saturation of the $\eta/S\ge 1/(4\pi)$ bound is correlated with the existence of a generalised Smarr relation for the planar black-hole solutions, we investigate this in detail for the general black-hole solutions in these theories, focusing especially on the cases where the scalar field plays a non-trivial role and gives rise to an additional parameter in the space of solutions. We find that a generalised Smarr relation holds in all cases, and in fact it can be viewed as the bulk gravity dual of the statement of the saturation of the viscosity to entropy bound. We obtain the generalised Smarr relation, whose existence depends upon a scaling symmetry of the planar black-hole solutions, by two different but related methods, one based on integrating the first law of thermodynamics, and the other based on the construction of a conserved Noether charge.

Interior dynamics of neutral and charged black holes

In this paper, we explore the interior dynamics of neutral and charged black holes. Scalar collapses in flat, Schwarzschild, and Reissner-Nordstrom geometries are simulated. We examine the dynamics in the vicinities of the central singularity of a Schwarzschild black hole and of the Inner horizon of a Reissner-Nordstrom black hole. In simulating scalar collapses in Schwarzschild and Reissner-Nordstrom geometries, Kruskal and Kruskal-like coordinates are used, respectively, with the presence of a scalar field being taken into account. It is found that, besides near the Inner horizons of Reissner-Nordstrom and Kerr black holes, mass inflation also takes place near the central singularity in neutral scalar collapse. Approximate analytic expressions for different types of mass inflation are partially obtained via a close interplay between numerical and analytical approaches and an examination of the connections between Schwarzschild black holes, Reissner-Nordstrom black holes, neutral collapse, and charge scattering. We argue that the mass inflations near the central singularity and the Inner horizon are related to the localness of the dynamics in strong gravity regions. This is in accord with the Belinskii, Khalatnikov, and Lifshitz conjecture.

It's a dark, dark world: Background evolution of interacting $\phi$CDM models beyond simple exponential potentials

We study the background cosmological dynamics with a three component source content: radiation fluid, a barotropic fluid to mimic the matter sector and a single scalar field which can act as dark energy giving rise to the late-time accelerated phase. Using the well-known dimensionless variables, we cast the dynamical equations into an autonomous system of ordinary differential equations (ASODE), which are studied by computing the fixed points and the conditions for their stability. The matter fluid and the scalar field are taken to be uncoupled at first and later, we consider a coupling between the two of the form $Q = \sqrt{2/3}\kappa\beta\rho_m\dot{\phi}$ where $\rho_m$ is the barotropic fluid density. The key point of our analysis is that for the closure of ASODE, we only demand that the jerk, $\Gamma = V V"/V’^2$ is a function of acceleration, $z = – M_p V’/ V$, that is, $\Gamma = 1+ f(z)$. In this way, we are able to accommodate a large class of potentials that goes beyond the simple exponential potentials. The analysis is completely generic and \emph{independent} of the form of potential for the scalar field. As an illustration and confirmation of the analysis, we consider $f(z)$ of the forms $\mu/z^2$, $\mu/z$, $(\mu-z)/z^2$ and $(\mu-z)$ to numerically compute the evolution of cosmological parameters with and without coupling. Implications of the approach and the results are discussed.

It's a dark, dark world: Background evolution of interacting $\phi$CDM models beyond simple exponential potentials [Cross-Listing]

We study the background cosmological dynamics with a three component source content: radiation fluid, a barotropic fluid to mimic the matter sector and a single scalar field which can act as dark energy giving rise to the late-time accelerated phase. Using the well-known dimensionless variables, we cast the dynamical equations into an autonomous system of ordinary differential equations (ASODE), which are studied by computing the fixed points and the conditions for their stability. The matter fluid and the scalar field are taken to be uncoupled at first and later, we consider a coupling between the two of the form $Q = \sqrt{2/3}\kappa\beta\rho_m\dot{\phi}$ where $\rho_m$ is the barotropic fluid density. The key point of our analysis is that for the closure of ASODE, we only demand that the jerk, $\Gamma = V V"/V’^2$ is a function of acceleration, $z = – M_p V’/ V$, that is, $\Gamma = 1+ f(z)$. In this way, we are able to accommodate a large class of potentials that goes beyond the simple exponential potentials. The analysis is completely generic and \emph{independent} of the form of potential for the scalar field. As an illustration and confirmation of the analysis, we consider $f(z)$ of the forms $\mu/z^2$, $\mu/z$, $(\mu-z)/z^2$ and $(\mu-z)$ to numerically compute the evolution of cosmological parameters with and without coupling. Implications of the approach and the results are discussed.

Fermion Doubling in Loop Quantum Gravity

In this paper, we show that the Hamiltonian approach to loop quantum gravity has a fermion doubling problem. To obtain this result, we couple loop quantum gravity to a free massless scalar and a chiral fermion field, gauge fixing the many fingered time gauge invariance by interpreting the scalar field as a physical clock. We expand around a quantum gravity state based on a regular lattice and consider the limit where the bare cosmological constant is large but the fermonic excitations have energies low in Planck units. We then make the case for identifying the energy spectrum in this approximation with that of a model of lattice fermion theory which is known to double.

Fermion Doubling in Loop Quantum Gravity [Cross-Listing]

In this paper, we show that the Hamiltonian approach to loop quantum gravity has a fermion doubling problem. To obtain this result, we couple loop quantum gravity to a free massless scalar and a chiral fermion field, gauge fixing the many fingered time gauge invariance by interpreting the scalar field as a physical clock. We expand around a quantum gravity state based on a regular lattice and consider the limit where the bare cosmological constant is large but the fermonic excitations have energies low in Planck units. We then make the case for identifying the energy spectrum in this approximation with that of a model of lattice fermion theory which is known to double.

Loop quantum gravity coupled to a scalar field

We reconsider the Rovelli-Smolin model of gravity coupled to the Klein-Gordon time field with an eye towards capturing the degrees of freedom of the scalar field lost in the framework in which time is deparametrized by the scalar field. Several new results for loop quantum gravity are obtained: (i) a Hilbert space for the gravity-matter system and a non-standard representation of the scalar field thereon is constructed, (ii) a new operator for the scalar constraint of the coupled system is defined and investigated, (iii) methods for solving the constraint are developed. Commutators of the new constraint do not vanish, but seem to reproduce a part of the Dirac algebra. This, however, poses problems for finding solutions. Hence the states we consider — and perhaps the whole setup — still needs some improvement. As a side result we describe a representation of the gravitational degrees of freedom in which the flux is diagonal. This representation bears a strong resemblance to the BF vacuum of Dittrich and Geiller.

Loop quantum gravity coupled to a scalar field [Cross-Listing]

We reconsider the Rovelli-Smolin model of gravity coupled to the Klein-Gordon time field with an eye towards capturing the degrees of freedom of the scalar field lost in the framework in which time is deparametrized by the scalar field. Several new results for loop quantum gravity are obtained: (i) a Hilbert space for the gravity-matter system and a non-standard representation of the scalar field thereon is constructed, (ii) a new operator for the scalar constraint of the coupled system is defined and investigated, (iii) methods for solving the constraint are developed. Commutators of the new constraint do not vanish, but seem to reproduce a part of the Dirac algebra. This, however, poses problems for finding solutions. Hence the states we consider — and perhaps the whole setup — still needs some improvement. As a side result we describe a representation of the gravitational degrees of freedom in which the flux is diagonal. This representation bears a strong resemblance to the BF vacuum of Dittrich and Geiller.

Scrutinizing the Alignment Limit in Two-Higgs-Doublet Models. Part 1: $m_h = 125$ GeV

In the alignment limit of a multi-doublet Higgs sector, one of the Higgs mass eigenstates aligns with the direction of the scalar field vacuum expectation values, and its couplings approach those of the Standard Model (SM) Higgs boson. We consider CP-conserving Two-Higgs-Doublet Models (2HDMs) of Type I and Type II near the alignment limit in which the lighter of the two CP-even Higgs bosons, $h$, is the SM-like state observed at 125 GeV. In particular, we focus on the 2HDM parameter regime where the coupling of $h$ to gauge bosons approaches that of the SM. We review the theoretical structure and analyze the phenomenological implications of the regime of alignment limit without decoupling, in which the other Higgs scalar masses are not significantly larger than $m_h$ and thus do not decouple from the effective theory at the electroweak scale. For the numerical analysis, we perform scans of the 2HDM parameter space employing the software packages 2HDMC and Lilith, taking into account all relevant pre-LHC constraints, the latest constraints from the measurements of the 125 GeV Higgs signal at the LHC, as well as the most recent limits coming from searches for heavy Higgs-like states. We contrast these results with the alignment limit achieved via the decoupling of heavier scalar states, where $h$ is the only light Higgs scalar. Implications for Run 2 at the LHC, including expectations for observing the other scalar states, are also discussed.

Scrutinizing the Alignment Limit in Two-Higgs-Doublet Models. Part 1: $m_h = 125$ GeV [Replacement]

In the alignment limit of a multi-doublet Higgs sector, one of the Higgs mass eigenstates aligns with the direction of the scalar field vacuum expectation values, and its couplings approach those of the Standard Model (SM) Higgs boson. We consider CP-conserving Two-Higgs-Doublet Models (2HDMs) of Type I and Type II near the alignment limit in which the lighter of the two CP-even Higgs bosons, $h$, is the SM-like state observed at 125 GeV. In particular, we focus on the 2HDM parameter regime where the coupling of $h$ to gauge bosons approaches that of the SM. We review the theoretical structure and analyze the phenomenological implications of the regime of alignment limit without decoupling, in which the other Higgs scalar masses are not significantly larger than $m_h$ and thus do not decouple from the effective theory at the electroweak scale. For the numerical analysis, we perform scans of the 2HDM parameter space employing the software packages 2HDMC and Lilith, taking into account all relevant pre-LHC constraints, the latest constraints from the measurements of the 125 GeV Higgs signal at the LHC, as well as the most recent limits coming from searches for heavy Higgs-like states. We contrast these results with the alignment limit achieved via the decoupling of heavier scalar states, where $h$ is the only light Higgs scalar. Implications for Run 2 at the LHC, including expectations for observing the other scalar states, are also discussed.

Coupled dark energy: a dynamical analysis with complex scalar field [Cross-Listing]

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

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.

A Cyclic Universe Approach to Fine Tuning

We present a closed bouncing universe model where the value of coupling constants is set by the dynamics of a ghost-like dilatonic scalar field. We show that adding a periodic potential for the scalar field leads to a cyclic Friedmann universe where the values of the couplings vary randomly from one cycle to the next. While the shuffling of values for the couplings happens during the bounce, within each cycle their time-dependence remains safely within present observational bounds for physically-motivated values of the model parameters. Our model presents an alternative to solutions of the fine tuning problem based on string landscape scenarios.

A Cyclic Universe Approach to Fine Tuning [Cross-Listing]

We present a closed bouncing universe model where the value of coupling constants is set by the dynamics of a ghost-like dilatonic scalar field. We show that adding a periodic potential for the scalar field leads to a cyclic Friedmann universe where the values of the couplings vary randomly from one cycle to the next. While the shuffling of values for the couplings happens during the bounce, within each cycle their time-dependence remains safely within present observational bounds for physically-motivated values of the model parameters. Our model presents an alternative to solutions of the fine tuning problem based on string landscape scenarios.

Towards relativistic quantum geometry [Cross-Listing]

We obtain a gauge-invariant relativistic quantum geometry by using a Weylian-like integrable manifold with a geometric scalar field which provides a gauge-invariant relativistic quantum theory in which the algebra of the Weylian-like field depends on observers. An example for a Reisnn\"er-Nordstr\"om black-hole is studied.

Towards relativistic quantum geometry [Cross-Listing]

We obtain a gauge-invariant relativistic quantum geometry by using a Weylian-like integrable manifold with a geometric scalar field which provides a gauge-invariant relativistic quantum theory in which the algebra of the Weylian-like field depends on observers. An example for a Reisnn\"er-Nordstr\"om black-hole is studied.

Towards relativistic quantum geometry

We obtain a gauge-invariant relativistic quantum geometry by using a Weylian-like integrable manifold with a geometric scalar field which provides a gauge-invariant relativistic quantum theory in which the algebra of the Weylian-like field depends on observers. An example for a Reisnn\"er-Nordstr\"om black-hole is studied.

A new halo model for clusters of galaxies

This paper presents a model for the dark halos of galaxy clusters in the framework of Weyl geometric scalar tensor theory with a MOND-like approximation in the weak field static limit. The basics of this approach are introduced in the first part of the paper; then a three component halo model is derived (without presupposing prior knowledge of Weyl geometric gravity). The cluster halo is constituted by the scalar field energy and the phantom energy of the gravitational structure, thus transparent rather than "dark". It is completely determined by the baryonic mass distribution of hot gas and stars. The model is tested against recent observational data for 19 clusters. The total mass of Coma and 15 other clusters is correctly predicted on the basis of data on baryonic mass in the bounds of the error intervals (1 sigma); one cluster lies in the 2 sigma interval, two more in 3 sigma.

A new halo model for clusters of galaxies [Cross-Listing]

This paper presents a model for the dark halos of galaxy clusters in the framework of Weyl geometric scalar tensor theory with a MOND-like approximation in the weak field static limit. The basics of this approach are introduced in the first part of the paper; then a three component halo model is derived (without presupposing prior knowledge of Weyl geometric gravity). The cluster halo is constituted by the scalar field energy and the phantom energy of the gravitational structure, thus transparent rather than "dark". It is completely determined by the baryonic mass distribution of hot gas and stars. The model is tested against recent observational data for 19 clusters. The total mass of Coma and 15 other clusters is correctly predicted on the basis of data on baryonic mass in the bounds of the error intervals (1 sigma); one cluster lies in the 2 sigma interval, two more in 3 sigma.

A new halo model for clusters of galaxies [Replacement]

This paper presents a model for the dark halos of galaxy clusters in the framework of Weyl geometric scalar tensor theory with a MOND-like approximation in the weak field static limit. The basics of this approach are introduced in the first part of the paper; then a three component halo model is derived (without presupposing prior knowledge of Weyl geometric gravity). The cluster halo is constituted by the scalar field energy and the phantom energy of the gravitational structure, thus transparent rather than "dark". It is completely determined by the baryonic mass distribution of hot gas and stars. The model is tested against recent observational data for 19 clusters. The total mass of Coma and 14 other clusters is correctly predicted on the basis of data on baryonic mass in the bounds of the error intervals (1 sigma); two clusters lie in the $2\,\sigma$ interval, two more are outliers.

A new halo model for clusters of galaxies [Replacement]

This paper presents a model for the dark halos of galaxy clusters in the framework of Weyl geometric scalar tensor theory with a MOND-like approximation in the weak field static limit. The basics of this approach are introduced in the first part of the paper; then a three component halo model is derived (without presupposing prior knowledge of Weyl geometric gravity). The cluster halo is constituted by the scalar field energy and the phantom energy of the gravitational structure, thus transparent rather than "dark". It is completely determined by the baryonic mass distribution of hot gas and stars. The model is tested against recent observational data for 19 clusters. The total mass of Coma and 14 other clusters is correctly predicted on the basis of data on baryonic mass in the bounds of the error intervals (1 sigma); two clusters lie in the $2\,\sigma$ interval, two more are outliers.

Scalar - Tensor gravity with scalar -matter direct coupling and its cosmological probe

SNIA and CMB datasets have shown both of evolving Newton’s "constant" and a signature of the coupling of scalar field to matter. These observations motivate the consideration of the scalar-matter coupling in Jordan frame in the framework of scalar-tensor gravity. So far, majority of the works on the coupling of scalar matter has performed in Einstein frame in the framework of minimally coupled scalar fields. In this work, we generalize the original scalar-tensor theories of gravity introducing a direct coupling of scalar to matter in the Jordan frame. The combined consideration of both evolving Newton’s constant and scalar-matter coupling using the recent observation datasets, shows features different from the previous works. The analysis shows a vivid signature of the scalar-matter coupling. The variation rate of the Newton’s constant is obtained rather greater than that determined in the previous works.

Scalar - Tensor gravity with scalar -matter direct coupling and its cosmological probe [Cross-Listing]

SNIA and CMB datasets have shown both of evolving Newton’s "constant" and a signature of the coupling of scalar field to matter. These observations motivate the consideration of the scalar-matter coupling in Jordan frame in the framework of scalar-tensor gravity. So far, majority of the works on the coupling of scalar matter has performed in Einstein frame in the framework of minimally coupled scalar fields. In this work, we generalize the original scalar-tensor theories of gravity introducing a direct coupling of scalar to matter in the Jordan frame. The combined consideration of both evolving Newton’s constant and scalar-matter coupling using the recent observation datasets, shows features different from the previous works. The analysis shows a vivid signature of the scalar-matter coupling. The variation rate of the Newton’s constant is obtained rather greater than that determined in the previous works.

Scalar - Tensor gravity with scalar -matter direct coupling and its cosmological probe [Cross-Listing]

SNIA and CMB datasets have shown both of evolving Newton’s "constant" and a signature of the coupling of scalar field to matter. These observations motivate the consideration of the scalar-matter coupling in Jordan frame in the framework of scalar-tensor gravity. So far, majority of the works on the coupling of scalar matter has performed in Einstein frame in the framework of minimally coupled scalar fields. In this work, we generalize the original scalar-tensor theories of gravity introducing a direct coupling of scalar to matter in the Jordan frame. The combined consideration of both evolving Newton’s constant and scalar-matter coupling using the recent observation datasets, shows features different from the previous works. The analysis shows a vivid signature of the scalar-matter coupling. The variation rate of the Newton’s constant is obtained rather greater than that determined in the previous works.

A realistic model of a neutron star in minimal dilatonic gravity [Replacement]

We present a derivation of the basic equations and boundary conditions for relativistic static spherically symmetric stars (SSSS) in the model of minimal dilatonic gravity (MDG) which offers an alternative and simultaneous description of the effects of dark matter (DM) and dark energy (DE) using one dilaton field $\Phi$. The numerical results for a realistic equation of state (EOS) MPA1 of neutron matter are presented for the first time. The three very different scales, the Compton length of the scalar field $\lambda_\Phi$, the star’s radius $r^*$, and the finite radius of the MDG Universe $r_{U}$ are a source of numerical difficulties. Owing to the introduction of a new dark scalar field $\varphi=\ln(1+\ln\Phi)$, we have been able to study numerically an unprecedentedly large interval of $\lambda_\Phi$ and have discovered the existence of $\lambda_\Phi^{crit}\approx 2.1$\ km for a neutron star with MPA1 EOS. This is related to the bifurcation of the physical domain in the phase space of the system. Some novel physical consequences are discussed.

A realistic model of a neutron star in minimal dilatonic gravity [Replacement]

We present a derivation of the basic equations and boundary conditions for relativistic static spherically symmetric stars (SSSS) in the model of minimal dilatonic gravity (MDG) which offers an alternative and simultaneous description of the effects of dark matter (DM) and dark energy (DE) using one dilaton field $\Phi$. The numerical results for a realistic equation of state (EOS) MPA1 of neutron matter are presented for the first time. The three very different scales, the Compton length of the scalar field $\lambda_\Phi$, the star’s radius $r^*$, and the finite radius of the MDG Universe $r_{U}$ are a source of numerical difficulties. Owing to the introduction of a new dark scalar field $\varphi=\ln(1+\ln\Phi)$, we have been able to study numerically an unprecedentedly large interval of $\lambda_\Phi$ and have discovered the existence of $\lambda_\Phi^{crit}\approx 2.1$\ km for a neutron star with MPA1 EOS. This is related to the bifurcation of the physical domain in the phase space of the system. Some novel physical consequences are discussed.

A realistic model of neutron star in minimal dilatonic gravity [Cross-Listing]

We present derivation of the basic equations and boundary conditions for relativistic static spherically symmetric stars (SSSS) in the model of minimal dilatonic gravity (MDG) which offers an alternative and simultaneous description of the effects of dark matter (DM) and dark energy (DE) using one dilaton field $\Phi$. The numerical results for a realistic equation of state (EOS) MPA1 of neutron matter are represented for the first time. The existing three very different scales: the Compton length of the scalar field $\lambda_\Phi$, the star’s radius $r^*$, and the finite radius of MDG Universe $r_{U}$ are a source of numerical difficulties. Owing to introduction of a new dark scalar field $\varphi=\ln(1+\ln\Phi)$ we were able to study numerically an unprecedentedly large interval of $\lambda_\Phi$ and discovered existence of $\lambda_\Phi^{crit}\approx 2.1\, km$ for NS with MPA1 EOS. It is related with bifurcation of the physical domain in phase space of the system. Some novel physical consequences are discussed.

A realistic model of a neutron star in minimal dilatonic gravity [Replacement]

We present a derivation of the basic equations and boundary conditions for relativistic static spherically symmetric stars (SSSS) in the model of minimal dilatonic gravity (MDG) which offers an alternative and simultaneous description of the effects of dark matter (DM) and dark energy (DE) using one dilaton field $\Phi$. The numerical results for a realistic equation of state (EOS) MPA1 of neutron matter are presented for the first time. The three very different scales, the Compton length of the scalar field $\lambda_\Phi$, the star’s radius $r^*$, and the finite radius of the MDG Universe $r_{U}$ are a source of numerical difficulties. Owing to the introduction of a new dark scalar field $\varphi=\ln(1+\ln\Phi)$, we have been able to study numerically an unprecedentedly large interval of $\lambda_\Phi$ and have discovered the existence of $\lambda_\Phi^{crit}\approx 2.1$\ km for a neutron star with MPA1 EOS. This is related to the bifurcation of the physical domain in the phase space of the system. Some novel physical consequences are discussed.

A realistic model of neutron star in minimal dilatonic gravity [Replacement]

We present derivation of the basic equations and boundary conditions for relativistic static spherically symmetric stars (SSSS) in the model of minimal dilatonic gravity (MDG) which offers an alternative and simultaneous description of the effects of dark matter (DM) and dark energy (DE) using one dilaton field $\Phi$. The numerical results for a realistic equation of state (EOS) MPA1 of neutron matter are represented for the first time. The existing three very different scales: the Compton length of the scalar field $\lambda_\Phi$, the star’s radius $r^*$, and the finite radius of MDG Universe $r_{U}$ are a source of numerical difficulties. Owing to introduction of a new dark scalar field $\varphi=\ln(1+\ln\Phi)$ we were able to study numerically an unprecedentedly large interval of $\lambda_\Phi$ and discovered existence of $\lambda_\Phi^{crit}\approx 2.1\, km$ for NS with MPA1 EOS. It is related with bifurcation of the physical domain in phase space of the system. Some novel physical consequences are discussed.

 

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