Showing papers on "Scalar potential published in 2018"
TL;DR: In this article, the authors analyze the theoretical and phenomenological considerations for the electroweak phase transition and dark matter in an extension of the standard model with a complex scalar singlet (cxSM).
Abstract: We analyze the theoretical and phenomenological considerations for the electroweak phase transition and dark matter in an extension of the standard model with a complex scalar singlet (cxSM). In contrast with earlier studies, we use a renormalization group improved scalar potential and treat its thermal history in a gauge-invariant manner. We find that the parameter space consistent with a strong first-order electroweak phase transition (SFOEWPT) and present dark matter phenomenological constraints is significantly restricted compared to results of a conventional, gauge-noninvariant analysis. In the simplest variant of the cxSM, recent LUX data and a SFOEWPT require a dark matter mass close to half the mass of the standard model-like Higgs boson. We also comment on various caveats regarding the perturbative treatment of the phase transition dynamics.
131 citations
TL;DR: In this paper, the authors define a thermal resummation procedure based on partial dressing (PD) for general BSM calculations of phase transitions beyond the high-temperature approximation, which is numerically nearly as efficient as old incorrect methods, while yielding identical results to the full PD calculation.
Abstract: The consequences of phase transitions in the early universe are becoming testable in a variety of manners, from colliders physics to gravitational wave astronomy. In particular one phase transition we know of, the electroweak phase transition (EWPT), could potentially be first order in BSM scenarios and testable in the near future. If confirmed this could provide a mechanism for baryogenesis, which is one of the most important outstanding questions in physics. To reliably make predictions it is necessary to have full control of the finite temperature scalar potentials. However, as we show the standard methods used in BSM physics to improve phase transition calculations, resumming hard thermal loops, introduces significant errors into the scalar potential. In addition, the standard methods make it impossible to match theories to an EFT description reliably. In this paper we define a thermal resummation procedure based on partial dressing (PD) for general BSM calculations of phase transitions beyond the high-temperature approximation. Additionally, we introduce the modified optimized partial dressing (OPD) procedure, which is numerically nearly as efficient as old incorrect methods, while yielding identical results to the full PD calculation. This can be easily applied to future BSM studies of phase transitions in the early universe. As an example, we show that in unmixed singlet scalar extensions of the SM, the (O)PD calculations make new phenomenological predictions compared to previous analyses. An important future application is the study of EFTs at finite temperature.
117 citations
TL;DR: Results demonstrate a feasible, fast, oscillation-free and collision-free path planning of the proposed method, which is practically feasible that can be applied to both static and dynamic environments.
Abstract: This paper deals with the mobile robots path planning problem in the presence of scattered obstacles in a visually known environment. Utilizing the theory of charged particles’ potential fields and inspired by a key idea of the authors’ recent work, an optimization based approach is proposed to obtain an optimal and robust path planning solution. By assigning a potential function for each individual obstacle, the interaction of all scattered obstacles are integrated in a scalar potential surface (SPS) which strongly depends on the physical features of the mobile robot and obstacles. The optimum path is then obtained from a cost function optimization by attaining a trade-off between traversing the shortest path and avoiding collisions, simultaneously. Hence, irrespective of any physical constraints on the obstacles/mobile-robot and the adjacency of the target to the obstacles, the achieved results demonstrate a feasible, fast, oscillation-free and collision-free path planning of the proposed method. Utilizing a scalar decision variable makes it extremely simple in terms of mathematical computations and thus practically feasible that can be applied to both static and dynamic environments. Finally, simulation results verified the performance and fulfillment of the mentioned objectives of the approach.
96 citations
TL;DR: In this article, an alternative approach, based on an effective field theory framework, for a new scalar that dominantly couples to one specific SM fermion mass eigenstate is described.
Abstract: New singlet scalar bosons have broad phenomenological utility and feature prominently in many extensions of the standard model. Such scalars are often taken to have Higgs-like couplings to SM fermions in order to evade stringent flavor bounds, e.g., by assuming minimal flavor violation (MFV), which leads to a rather characteristic phenomenology. Here, we describe an alternative approach, based on an effective field theory framework, for a new scalar that dominantly couples to one specific SM fermion mass eigenstate. A simple flavor hypothesis ensures adequate suppression of new flavor changing neutral currents. We consider radiatively generated flavor changing neutral currents and scalar potential terms in such theories, demonstrating that they are often suppressed by small Yukawa couplings, and also describe the role of $CP$ symmetry. We further demonstrate that such scalars can have masses that are significantly below the electroweak scale while still being natural, provided they are sufficiently weakly coupled to ordinary matter. In comparison to other flavor scenarios, our framework is rather versatile since a single (or a few) desired scalar couplings may be investigated in isolation. We illustrate this by discussing in detail the examples of an up-specific scalar mediator to dark matter and a muon-specific scalar that may address the $\ensuremath{\sim}3\ensuremath{\sigma}$ muon anomalous magnetic moment discrepancy.
93 citations
TL;DR: In this paper, the analog effect of the Aharonov-Bohm effect for bound states in two relativistic quantum systems in a spacetime with a spacelike dislocation was investigated.
Abstract: We investigate the analog effect of the Aharonov–Bohm effect for bound states in two relativistic quantum systems in a spacetime with a spacelike dislocation. We assume that the topological defect has an internal magnetic flux. Then, we analyze the interaction of a charged particle with a uniform magnetic field in this topological defect spacetime, and thus, we extend this analysis to the confinement of a hard-wall potential and a linear scalar potential. Later, the interaction of the Klein–Gordon oscillator with a uniform magnetic field is analyzed. We first focus on the effects of torsion that stem from the spacetime with a spacelike dislocation and the geometric quantum phase. Then, we analyze the effects of torsion and the geometric quantum phase under the presence of a hard-wall potential and a linear scalar potential.
89 citations
TL;DR: This work derives and presents a Bayesian nonparametric probabilistic modeling approach for interpolation and extrapolation of the magnetic field using Maxwell's equations and rewriting the GP model in terms of a Hilbert space representation.
Abstract: Anomalies in the ambient magnetic field can be used as features in indoor positioning and navigation. By using Maxwell's equations, we derive and present a Bayesian nonparametric probabilistic modeling approach for interpolation and extrapolation of the magnetic field. We model the magnetic field components jointly by imposing a Gaussian process (GP) prior to the latent scalar potential of the magnetic field. By rewriting the GP model in terms of a Hilbert space representation, we circumvent the computational pitfalls associated with GP modeling and provide a computationally efficient and physically justified modeling tool for the ambient magnetic field. The model allows for sequential updating of the estimate and time-dependent changes in the magnetic field. The model is shown to work well in practice in different applications. We demonstrate mapping of the magnetic field both with an inexpensive Raspberry Pi powered robot and on foot using a standard smartphone.
63 citations
TL;DR: In this paper, the Coulomb-type potential with a screw dislocation was investigated in a topological defect spacetime with an internal magnetic field and the Klein-Gordon oscillator.
Abstract: We investigate topological effects on the interaction of a scalar field with a Coulomb-type potential in a spacetime with a screw dislocation (space-like dislocation). We also consider the topological defect with an internal magnetic field. Later, we investigate the interaction of a scalar field with a Coulomb-type potential plus another Coulomb-type potential (gauge potential), a uniform magnetic field, the Klein-Gordon oscillator and a linear scalar potential in this topological defect spacetime. Then, by searching for analytical solutions to the Klein-Gordon equation in the spacetime with a screw dislocation, we obtain analogues effects of the Aharonov-Bohm effect for bound states.
63 citations
TL;DR: In this paper, the authors discuss the local Weyl symmetry and its spontaneous breaking and apply it to model building beyond the Standard Model (SM) and inflation, and show that successful inflation is then possible with one of these scalar fields identified as the inflaton.
Abstract: We discuss the local (gauged) Weyl symmetry and its spontaneous breaking and apply it to model building beyond the Standard Model (SM) and inflation. In models with non-minimal couplings of the scalar fields to the Ricci scalar, that are conformal invariant, the spontaneous generation by a scalar field(s) vev of a positive Newton constant demands a negative kinetic term for the scalar field, or vice-versa. This is naturally avoided in models with additional Weyl gauge symmetry. The Weyl gauge field $\omega_\mu$ couples to the scalar sector but not to the fermionic sector of a SM-like Lagrangian. The field $\omega_\mu$ undergoes a Stueckelberg mechanism and becomes massive after "eating" the (radial mode) would-be-Goldstone field (dilaton $\rho$) in the scalar sector. Before the decoupling of $\omega_\mu$, the dilaton can act as UV regulator and maintain the Weyl symmetry at the {\it quantum} level, with relevance for solving the hierarchy problem. After the decoupling of $\omega_\mu$, the scalar potential depends only on the remaining (angular variables) scalar fields, that can be the Higgs field, inflaton, etc. We show that successful inflation is then possible with one of these scalar fields identified as the inflaton. While our approach is derived in the Riemannian geometry with $\omega_\mu$ introduced to avoid ghosts, the natural framework is that of Weyl geometry which for the same matter spectrum is shown to generate the same Lagrangian, up to a total derivative.
58 citations
TL;DR: In this paper, the cosmological abundance of dark matter can be significantly influenced by the temperature dependence of particle masses and vacuum expectation values, and three simple freeze-in models are proposed.
Abstract: The cosmological abundance of dark matter can be significantly influenced by the temperature dependence of particle masses and vacuum expectation values. We illustrate this point in three simple freeze-in models. The first one, which we call kinematically induced freeze-in, is based on the observation that the effective mass of a scalar temporarily becomes very small as the scalar potential undergoes a second order phase transition. This opens dark matter production channels that are otherwise forbidden. The second model we consider, dubbed vev-induced freeze-in, is a fermionic Higgs portal scenario. Its scalar sector is augmented compared to the Standard Model by an additional scalar singlet, S, which couples to dark matter and temporarily acquires a vacuum expectation value (a two-step phase transition or “vev flip-flop”). While 〈S〉 ≠ 0, the modified coupling structure in the scalar sector implies that dark matter production is significantly enhanced compared to the 〈S〉 = 0 phases realised at very early times and again today. The third model, which we call mixing-induced freeze-in, is similar in spirit, but here it is the mixing of dark sector fermions, induced by non-zero 〈S〉, that temporarily boosts the dark matter production rate. For all three scenarios, we carefully dissect the evolution of the dark sector in the early Universe. We compute the DM relic abundance as a function of the model parameters, emphasising the importance of thermal corrections and the proper treatment of phase transitions in the calculation.
57 citations
TL;DR: In this article, a linear scalar potential is introduced into the relativistic quantum dynamics of a scalar particle in a Godel-type spacetime in the presence of a topological defect.
Abstract: Based on the studies of confinement of quarks, we introduce a linear scalar potential into the relativistic quantum dynamics of a scalar particle. Then, we analyse the linear confinement of a relativistic scalar particle in a Godel-type spacetime in the presence of a topological defect. We consider a Godel-type spacetime associated with null curvature, i.e., the Som-Raychaudhuri spacetime, which is characterized by the presence of vorticity in the spacetime. Then, we search for analytical solutions to the Klein-Gordon equation and analyse the influence of the topology of the cosmic string and the vorticity on the relativistic energy levels.
54 citations
CERN1
TL;DR: In this paper, the authors studied the existence and stability of classical de Sitter solutions of type II supergravities with parallel Dp-branes and orientifold Op-planes.
Abstract: We study the existence and stability of classical de Sitter solutions of type II supergravities with parallel Dp-branes and orientifold Op-planes. Together with the dilaton and volume scalar fields, we consider a third one that distinguishes between parallel and transverse directions to the Dp/Op. We derive the complete scalar potential for these three fields. This formalism allows us to reproduce known constraints obtained in 10d, and to derive new ones. Specifying to group manifolds with constant fluxes, we exclude a large region of parameter space, forbidding de Sitter solutions on nilmanifolds, semi-simple group manifolds, and some solvmanifolds. In the small remaining region, we identify a stability island, where the three scalars could be stabilized in any de Sitter solution. We discuss these results in the swampland context.
TL;DR: In this paper, an extension of the SM Higgs sector by a Higgs triplet was considered and the scalar potential of the Higgs particle was evaluated through the unitarity of the scattering matrix.
Abstract: We examine an extension of the SM Higgs sector by a Higgs triplet taking into consideration the discovery of a Higgs-like particle at the LHC with mass around 125 GeV. We evaluate the bounds on the scalar potential through the unitarity of the scattering matrix. Considering the cases with and without $$\mathbb {Z}_2$$
-symmetry of the extra triplet, we derive constraints on the parameter space. We identify the region of the parameter space that corresponds to the stability and metastability of the electroweak vacuum. We also show that at large field values the scalar potential of this model is suitable to explain inflation.
TL;DR: In this paper, a linear scalar potential was introduced into the relativistic quantum dynamics of a scalar particle and the authors analyzed the linear confinement of the particle in a Godel-type spacetime with null curvature.
Abstract: Based on the studies of confinement of quarks, we introduce a linear scalar potential into the relativistic quantum dynamics of a scalar particle. Then we analyze the linear confinement of a relativistic scalar particle in a Godel-type spacetime in the presence of a topological defect. We consider a Godel-type spacetime associated with null curvature, i.e., the Som–Raychaudhuri spacetime, which is characterized by the presence of vorticity in the spacetime. Then we search for analytical solutions to the Klein–Gordon equation and analyze the influence of the topology of the cosmic string and the vorticity on the relativistic energy levels.
TL;DR: In this paper, the authors investigated a possible scenario arising from the Lorentz symmetry violation governed by a background tensor field on a scalar field subject to the Klein-Gordon oscillator, where this possible scenario gives rise to a linear central potential.
Abstract: Inspired by the Standard Model Extension, we have investigated a possible scenario arising from the Lorentz symmetry violation governed by a background tensor field on a scalar field subject to the Klein–Gordon oscillator, where this possible scenario gives rise to a linear central potential. We analyse the behaviour of the relativistic quantum oscillator under the influence of a Coulomb-type scalar potential in this background. Then, we solve the Klein–Gordon equation analytically and discuss the influence of the background which violates the Lorentz symmetry in the relativistic energy levels.
TL;DR: In this article, a method for renormalisation group improvement of the effective potential of a quantum field theory with an arbitrary number of scalar fields is presented. But the method does not address the problem of finding a suitable field-dependent value for the renormalization scale.
Abstract: We present a new method for renormalisation group improvement of the effective potential of a quantum field theory with an arbitrary number of scalar fields. The method amounts to solving the renormalisation group equation for the effective potential with the boundary conditions chosen on the hypersurface where quantum corrections vanish. This hypersurface is defined through a suitable choice of a field-dependent value for the renormalisation scale. The method can be applied to any order in perturbation theory and it is a generalisation of the standard procedure valid for the one-field case. In our method, however, the choice of the renormalisation scale does not eliminate individual logarithmic terms but rather the entire loop corrections to the effective potential. It allows us to evaluate the improved effective potential for arbitrary values of the scalar fields using the tree-level potential with running coupling constants as long as they remain perturbative. This opens the possibility of studying various applications which require an analysis of multi-field effective potentials across different energy scales. In particular, the issue of stability of the scalar potential can be easily studied beyond tree level.
TL;DR: Numerical examples validate the efficiency and stability of the novel formulation in solving both EM scattering and circuit problems over a wide frequency range up to very low frequencies.
Abstract: In this paper, we propose a potential-based integral equation solver for low-frequency electromagnetic (EM) problems. In this formulation, the scalar potential ( $\Phi $ ) equation is solved in tandem with the vector potential ( $\textbf {A}$ ) equation. The resulting system is immune to low-frequency catastrophe and accurate in capturing the electrostatic and magnetostatic physics. The fast convergence of the new $\textbf {A}$ - $\Phi $ system, which is a typical symmetric saddle point problem, is made possible through the design of an appropriate left constraint preconditioner. Numerical examples validate the efficiency and stability of the novel formulation in solving both EM scattering and circuit problems over a wide frequency range up to very low frequencies.
TL;DR: In this article, the authors studied the thermodynamics of black hole solutions and their thermodynamics in the Einstein-scalar theories and found that they exhibit conformal thermodynamics and are non-trivial holographic RG flows.
Abstract: Black hole solutions and their thermodynamics are studied in Einstein-scalar theories. The associated zero-temperature solutions are non-trivial holographic RG flows. These include solutions which skip intermediate extrema of the bulk scalar potential or feature an inversion of the direction of the flow of the coupling (bounces). At finite temperature, a complex set of branches of black hole solutions is found. In some cases, first order phase transitions are found between the black-hole branches. In other cases, black hole solutions are found to exist even for boundary conditions which did not allow a zero-temperature vacuum flow. Finite-temperature solutions driven solely by the vacuum expectation value of a perturbing operator (zero source) are found and studied. Such solutions exist generically (i.e. with no special tuning of the potential) in theories in which the vacuum flows feature bounces. It is found that they exhibit conformal thermodynamics.
TL;DR: In this paper, the action of three-dimensional Einstein-Maxwell-dilaton gravity theory has been obtained from that of scalar-tensor modified gravity theory coupled to the Maxwell's electrodynamics as the matter field.
Abstract: Making use of the suitable transformation relations, the action of three-dimensional Einstein-Maxwell-dilaton gravity theory has been obtained from that of scalar-tensor modified gravity theory coupled to the Maxwell's electrodynamics as the matter field. Two new classes of the static three-dimensional charged dilatonic black holes, as the exact solutions to the coupled scalar, electromagnetic and gravitational field equations, have been obtained in the Einstein frame. Also, it has been found that the scalar potential can be written in the form of a generalized Liouville-type potential. The conserved black hole charge and masses as well as the black entropy, temperature, and electric potential have been calculated from the geometrical and thermodynamical approaches, separately. Through comparison of the results arisen from these two alternative approaches, the validity of the thermodynamical first law has been proved for both of the new black hole solutions in the Einstein frame. Making use of the canonical ensemble method, a black hole stability or phase transition analysis has been performed. Regarding the black hole heat capacity, with the black hole charge as a constant, the points of type-1 and type-2 phase transitions have been determined. Also, the ranges of the black hole horizon radius at which the Einstein black holes are thermally stable have been obtained for both of the new black hole solutions. Then making use of the inverse transformation relations, two new classes of the string black hole solutions have been obtained from their Einstein counterpart. The thermodynamics and thermal stability of the new string black hole solutions have been investigated. It has been found that thermodynamic properties of the new charged black holes are identical in the Einstein and Jordan frames.
TL;DR: In this article, the authors explore the dynamics and observational predictions of the warm little inflaton scenario, presently the simplest realization of warm inflation within a concrete quantum field theory construction, and compute the properties of the primordial spectrum of scalar curvature perturbations and the tensor-to-scalar ratio in the allowed parametric regions.
Abstract: We explore the dynamics and observational predictions of the warm little inflaton scenario, presently the simplest realization of warm inflation within a concrete quantum field theory construction. We consider three distinct types of scalar potentials for the inflaton, namely chaotic inflation with a quartic monomial potential, a Higgs-like symmetry breaking potential and a non-renormalizable plateau-like potential. In each case, we determine the parametric regimes in which the dynamical evolution is consistent for 50-60 e-folds of inflation, taking into account thermal corrections to the scalar potential and requiring, in particular, that the two fermions coupled directly to the inflaton remain relativistic and close to thermal equilibrium throughout the slow-roll regime and that the temperature is always below the underlying gauge symmetry breaking scale. We then compute the properties of the primordial spectrum of scalar curvature perturbations and the tensor-to-scalar ratio in the allowed parametric regions and compare them with Planck data, showing that this scenario is theoretically and observationally successful for a broad range of parameter values.
TL;DR: In this article, a renormalization group analysis of the Coulomb interaction and quenched disorder is presented to study how Dirac cone tilting affects the low-energy properties.
Abstract: A two-dimensional Dirac semimetal with tilted Dirac cone has recently attracted increasing interest. The tilt of Dirac cone can be realized in a number of materials, including deformed graphene, surface state of topological crystalline insulator, and certain organic compounds. We study how Dirac cone tilting affects the low-energy properties by presenting a renormalization group analysis of the Coulomb interaction and quenched disorder. A random scalar potential or random vector potential along the tilting direction cannot exist on its own as it always dynamically generates a new type of disorder, which dominates at low energies and turns the system into a compressible diffusive metal. Consequently, the fermions acquire a finite disorder scattering rate. Moreover, the isolated band-touching point is replaced by a bulk Fermi arc in the Brillouin zone. These results are not qualitatively changed when the Coulomb interaction is incorporated. In comparison, random mass and random vector potential along the nontilting direction can exist individually, without generating other types of disorder. They both suppress tilt at low energies, and do not produce bulk Fermi arc. Upon taking the Coulomb interaction into account, the system enters into a stable quantum critical state, in which the fermion field acquires a finite anomalous dimension but the dynamical exponent $z=1$. These results indicate that Dirac cone tilt does lead to some qualitatively different low-energy properties compared to the untilted system.
TL;DR: In this article, a set of branches of black-hole solutions and their thermodynamics are studied in Einstein-scalar theories, including solutions that skip intermediate extrema of the bulk scalar potential or feature an inversion of the direction of the flow of the coupling.
Abstract: Black hole solutions and their thermodynamics are studied in Einstein-scalar theories. The associated zero-temperature solutions are non-trivial holographic RG flows. These include solutions which skip intermediate extrema of the bulk scalar potential or feature an inversion of the direction of the flow of the coupling (bounces). At finite temperature, a complex set of branches of black hole solutions is found. In some cases, first order phase transitions are found between the black-hole branches. In other cases, black hole solutions are found to exist even for boundary conditions which {\em did not} allow a zero-temperature vacuum flow. Finite-temperature solutions driven solely by the vacuum expectation value of a perturbing operator (zero source) are found and studied. Such solutions exist generically (i.e. with no special tuning of the potential) in theories in which the vacuum flows feature bounces. It is found that they exhibit conformal thermodynamics. In special theories with a moduli space of vacua (at zero temperature), it is found that finite temperature destroys the existence of the moduli space.
TL;DR: In this article, it was shown that a modified Higgs potential generically results in a $Q$-dependent Higgs vacuum expectation value (VEV), which is severely excluded by the tests of the equivalence principle.
Abstract: The recently proposed de Sitter swampland conjecture excludes local extrema of a scalar potential with a positive energy density in a low energy effective theory. Under the conjecture, the observed dark energy cannot be explained by the cosmological constant. The local maximum of the Higgs potential at the symmetric point also contradicts with the conjecture. In order to make the Standard Model consistent with the conjecture, it has been proposed to introduce a quintessence field, $Q$, which couples to the cosmological constant and the local maximum of the Higgs potential. In this paper, we show that such a modified Higgs potential generically results in a $Q$-dependent Higgs vacuum expectation value (VEV). The $Q$-dependence of the Higgs VEV induces a long-range force, which is severely excluded by the tests of the equivalence principle. Besides, as the quintessence field is in motion, the Higgs VEV shows a time-dependence, which is also severely constrained by the measurements of the time-dependence of the proton-to-electron mass ratio. Those constraints require an additional fine-tuning which is justified neither by the swampland conjecture nor the anthropic principle. We further show that, even if such an unjustified fine-tuning condition is imposed at the tree level, radiative corrections upset it. Consequently, we argue that most of the habitable vacua in the string landscape are in tension with the phenomenological constraints.
TL;DR: In this article, a method for renormalisation group improvement of the effective potential of a quantum field theory with an arbitrary number of scalar fields is presented. But the method does not address the problem of finding a suitable field-dependent value for the renormalization scale.
Abstract: We present a new method for renormalisation group improvement of the effective potential of a quantum field theory with an arbitrary number of scalar fields. The method amounts to solving the renormalisation group equation for the effective potential with the boundary conditions chosen on the hypersurface where quantum corrections vanish. This hypersurface is defined through a suitable choice of a field-dependent value for the renormalisation scale. The method can be applied to any order in perturbation theory and it is a generalisation of the standard procedure valid for the one-field case. In our method, however, the choice of the renormalisation scale does not eliminate individual logarithmic terms but rather the entire loop corrections to the effective potential. It allows us to evaluate the improved effective potential for arbitrary values of the scalar fields using the tree-level potential with running coupling constants as long as they remain perturbative. This opens the possibility of studying various applications which require an analysis of multi-field effective potentials across different energy scales. In particular, the issue of stability of the scalar potential can be easily studied beyond tree level.
TL;DR: In this paper, the authors correct the vacuum stability conditions for two Higgs doublet models with real couplings, and show that the conditions for the two doublets are stable.
Abstract: We correct the vacuum stability conditions for two Higgs doublet model with real couplings.
TL;DR: In this paper, the authors studied nontopological Q-ball solutions of the Friedberg-Lee-Sirlin two-component model, and showed that they are classically stable for all range of values of angular frequency.
Abstract: We study nontopological Q-ball solutions of the ($3+1$)-dimensional Friedberg-Lee-Sirlin two-component model. The limiting case of the vanishing potential term yields an example of hairy Q-balls, which possess a long-range massless real field. We discuss the properties of these stationary field configurations and determine their domain of existence. Considering the Friedberg-Lee-Sirlin model, we present numerical evidence for the existence of spinning axially symmetric Q-balls with different parity. A solution of this type exists also in the limiting case of vanishing scalar potential. We find that the hairy Q-balls are classically stable for all range of values of angular frequency.
TL;DR: In this paper, the infrared limit of quantum gravity in the presence of a cosmological constant or effective potential for scalar fields was explored, where a graviton barrier is introduced to limit the maximal growth of the effective potential of scalar field fields.
Abstract: We explore the infrared limit of quantum gravity in the presence of a cosmological constant or effective potential for scalar fields For a positive effective scalar potential, one-loop perturbation theory around flat space is divergent due to an instability of the graviton propagator Functional renormalization solves this problem by a flow of couplings avoiding instabilities This leads to a graviton barrier limiting the maximal growth of the effective potential for large values of scalar fields In the presence of this barrier, variable gravity with a field dependent Planck mass can solve the cosmological constant problem by a cosmological runaway solution We discuss the naturalness of tiny values of the cosmological constant and cosmon mass due to a strong attraction towards an infrared fixed point
TL;DR: In this paper, a generalization of two-field α-attractors with a positive constant α was proposed, where the scalar manifold is a non-compact geometrically finite surface with a Riemannian metric.
TL;DR: In this article, a viable dark energy scenario in the presence of cubic Horndeski interactions and a standard scalar-field kinetic term with two exponential potentials was proposed and the existence of new scaling solutions along which the cubic coupling provided an important contribution to the field density that scales in the same way as the background fluid density.
Abstract: We propose a viable dark energy scenario in the presence of cubic Horndeski interactions and a standard scalar-field kinetic term with two exponential potentials. We show the existence of new scaling solutions along which the cubic coupling $G_3$ provides an important contribution to the field density that scales in the same way as the background fluid density. The solutions finally exit to the epoch of cosmic acceleration driven by a scalar-field dominated fixed point arising from the second exponential potential. We clarify the viable parameter space in which all the theoretically consistent conditions including those for the absence of ghost and Laplacian instabilities are satisfied on scaling and scalar-field dominated critical points. In comparison to Quintessence with the same scalar potential, we find that the cubic coupling gives rise to some novel features: (i) the allowed model parameter space is wider in that a steeper potential can drive the cosmic acceleration; (ii) the dark energy equation of state $w_{\phi}$ today can be closer to $-1$ relative to Quintessence; (iii) even if the density associated with the cubic coupling dominates over the standard field density in the scaling era, the former contribution tends to be suppressed at low redshifts. We also compute quantities associated with the growth of matter perturbations and weak lensing potentials under the quasi-static approximation in the sub-horizon limit and show that the cubic coupling leads to the modified evolution of perturbations which can be distinguished from Quintessence.
TL;DR: In this article, a new interaction for chiral models in four-dimensional (n = 1$ supergavity) is discussed, which contains a new arbitrary function in addition to the Kahler potential and superpotential.
Abstract: We discuss a new interaction for chiral models in four-dimensional ${\cal N}=1$ supergavity. It contains a new arbitrary function in addition to the Kahler potential and superpotential. Its features include linearly realized off-shell supersymmetry, Kahler-Weyl invariance and broken supersymmetry. The corresponding scalar potential is augmented by the arbitrary function which allows freedom in constructing low-energy phenomenological models and inflationary models rooted in supergravity.
TL;DR: The scalar potential for the exceptional field theory based on the affine symmetry group E$_9$ was constructed in this article, where the scalar fields appearing in this potential live formally on an infinite-dimensional extended spacetime and transform under E$9$ generalised diffeomorphisms.
Abstract: We construct the scalar potential for the exceptional field theory based on the affine symmetry group E$_9$. The fields appearing in this potential live formally on an infinite-dimensional extended spacetime and transform under E$_9$ generalised diffeomorphisms. In addition to the scalar fields expected from D=2 maximal supergravity, the invariance of the potential requires the introduction of new constrained scalar fields. Other essential ingredients in the construction include the Virasoro algebra and indecomposable representations of E$_9$. Upon solving the section constraint, the potential reproduces the dynamics of either eleven-dimensional or type IIB supergravity in the presence of two isometries.