Physical Scalar Field Research Articles

Critical collapse for the Starobinsky R2 model

We study gravitational collapse for the Starobinsky R2 model, a particular example of an f(r) theory, in a spherically symmetric spacetime. We add a massless scalar field as matter content to the spacetime. We work in the Einstein frame, where an additional scalar field arises due to the conformal transformation. As in general relativity, depending on the initial data, we found that the gravity scalar field and the physical scalar field can collapse, forming a black hole, in which the final solution is the Schwarzschild metric. We found the threshold of black hole formation through a fine-tuning method and studied critical collapse near this regime.

Flavonstrahlung in the B3− L2Z′ model at current and future colliders

The B3− L2Z′ model may explain some gross features of the fermion mass spectrum as well as b → sℓℓ anomalies. A TeV-scale physical scalar field associated with gauged U{(1)}_{B_3-{L}_2} spontaneous symmetry breaking, the flavon field ϑ, affects Higgs phenomenology via mixing. In this paper, we investigate the collider phenomenology of the flavon field. Higgs and W boson mass data are used to place bounds upon parameter space. We then examine flavonstrahlung (Z′ → Z′ϑ production) at colliders as a means to directly produce and discover flavon particles, which would provide direct empirical evidence tying the flavon to U{(1)}_{B_3-{L}_2} symmetry breaking. A 100 TeV FCC-hh or a 10 TeV muon collider would have high sensitivity to flavonstrahlung, whereas the HL-LHC can observe it only in extreme corners of parameter space.

LightAMR format standard and lossless compression algorithms for adaptive mesh refinement grids: RAMSES use case

The evolution of parallel I/O library as well as new concepts such as ‘in transit’ and ‘in situ’ visualization and analysis have been identified as key technologies to circumvent I/O bottleneck in pre-exascale applications. Nevertheless, data structure and data format can also be improved for both reducing I/O volume and improving data interoperability between data producer and data consumer. In this paper, we propose a very lightweight and purpose-specific post-processing data model for AMR meshes, called lightAMR. Based on this data model, we introduce a tree pruning algorithm that removes data redundancy from a fully threaded AMR octree. In addition, we present two lossless compression algorithms, one for the AMR grid structure description and one for AMR double/single precision physical quantity scalar fields. Then we present performance benchmarks on RAMSES simulation datasets of this new lightAMR data model and the pruning and compression algorithms. We show that our pruning algorithm can reduce the total number of cells from RAMSES AMR datasets by 10-40% without loss of information. Finally, we show that the RAMSES AMR grid structure can be compacted by ∼3 orders of magnitude and the float scalar fields can be compressed by a factor ∼1.2 for double precision and ∼1.3−1.5 in single precision with a compression speed of ∼1 GB/s.

Topological theory of physical fields

We study the topology associated with physical vector and scalar fields. A mathematical object, e.g., a ball, can be continuously deformed, without tearing or gluing, to make other topologically equivalent objects, e.g., a cube or a solid disk. If tearing or gluing get involved, i.e. the deformation is not continuous anymore, the initial topology will consequently change giving rise to a topologically distinct object, e.g., a torus. This simple concept in general topology may be employed in the study of physical systems described by fields. Instead of continuously deforming objects, we can take a continuously evolving field, with an appropriately defined topology, such that the topology remains unchanged in time unless the system undergoes an important physical change, e.g., a transition to a different energy state. For instance, a sudden change in the magnetic topology in an energetically relaxing plasma, a process called reconnection, strongly affects the dynamics, e.g., it is involved in launching solar flares and generating large scale magnetic fields in astrophysical objects. In this topological formalism, the magnetic topology in a plasma can spontaneously change due to the presence of dissipative terms in the induction equation which break its time symmetry. We define a topology for the vector field in the phase space . As for scalar fields represented by a perfect fluid, e.g., the inhomogeneous inflaton or Higgs fields, the fluid velocity defines the corresponding topology. The vector field topology in its corresponding phase space will be preserved in time if certain conditions including time reversal invariance are satisfied by the field and its governing differential equation. Otherwise, the field’s topology can suddenly change at some point, similar to a spontaneously broken symmetry, as time advances, e.g., corresponding to an energy transition.

Breaking of scaling symmetry by massless scalar on de Sitter

We study the response of a classical massless minimally coupled scalar to a static point scalar charge on de Sitter. By considering explicit solutions of the problem we conclude that – even though the dynamics formally admits dilatation (scaling) symmetry – the physical scalar field profile necessarily breaks the symmetry. This is an instance of symmetry breaking in classical physics due to large infrared effects. The gravitational backreaction, on the other hand, does respect dilatation symmetry, making this an example of symmetry non-inheritance phenomenon.

Long lived light scalars as probe of low scale seesaw models

We point out that in generic TeV scale seesaw models for neutrino masses with local B–L symmetry breaking, there is a phenomenologically allowed range of parameters where the Higgs field responsible for B–L symmetry breaking leaves a physical real scalar field with mass around GeV scale. This particle (denoted here by H3) is weakly mixed with the Standard Model Higgs field (h) with mixing θ1≲mH3/mh, barring fine-tuned cancellation. In the specific case when the B–L symmetry is embedded into the TeV scale left–right seesaw scenario, we show that the bounds on the h–H3 mixing θ1 become further strengthened due to low energy flavor constraints, thus forcing the light H3 to be long lived, with displaced vertex signals at the LHC. The property of left–right TeV scale seesaw models are such that they make the H3 decay to two photons as the dominant mode. This is in contrast with a generic light scalar that mixes with the SM Higgs boson, which could also have leptonic and hadronic decay modes with comparable or larger strength. We discuss the production of this new scalar field at the LHC and show that it leads to testable displaced vertex signals of collimated photon jets, which is a new distinguishing feature of the left–right seesaw model. We also study a simpler version of the model where the SU(2)R breaking scale is much higher than the O(TeV) U(1)B–L breaking scale, in which case the production and decay of H3 proceed differently, but its long lifetime feature is still preserved for a large range of parameters. Thus, the search for such long-lived light scalar particles provides a new way to probe TeV scale seesaw models for neutrino masses at colliders.

A note on conformally compactified connection dynamics tailored for anti-de Sitter space

A framework conceptually based on the conformal techniques employed to study the structure of the gravitational field at infinity is set up in the context of loop quantum gravity to describe asymptotically anti-de Sitter quantum spacetimes. A conformal compactification of the spatial slice is performed, which, in terms of the rescaled metric, has now finite volume, and can thus be conveniently described by spin networks states. The conformal factor used is a physical scalar field, which has the necessary asymptotics for many asymptotically AdS black hole solutions.

Spherical vacuum and scalar collapse for the StarobinskyR2model

Spherical vacuum and scalar collapse for the Starobinsky R^2 model is simulated. Obtained by considering the quantum-gravitational effects, this model would admit some cases of singularity-free cosmological spacetimes. It is found, however, that in vacuum and scalar collapse, when f' or the physical scalar field is strong enough, a black hole including a central singularity can be formed. In addition, near the central singularity, gravity dominates the repulsion from the potential, so that in some circumstances the Ricci scalar is pushed to infinity by gravity. Therefore, the semiclassical effects as included here do not avoid the singularity problem in general relativity. A strong physical scalar field can prevent the Ricci scalar from growing to infinity. Vacuum collapse for the RlnR model is explored, and it is observed that for this model the Ricci scalar can also go to infinity as the central singularity is approached. Therefore, this feature seems universal in vacuum and scalar collapse in f(R) gravity.

An improved radiation model and its applicability for understanding commuting patterns in Hungary

Several empirical models aimed at describing human mobility have been proposed in the past. Most of them are based on an unjustified analogy, with a focus on gravity and physical vector or scalar fields. Recently, however, statistical physicists introduced a new category of models that are theoretically motivated by a few simple and reasonable socio-economic assumptions. The Radiation Model (Simini et al. 2012) and the Radiation Model with Selection (Simini–Maritan–Neda 2013) are such successful approaches. Here, we introduce a new version of the radiation model, the Travel Cost Optimized Radiation Model, and test its applicability for describing the commuting patterns in Hungary. We compare critically the performance of this model with the results of the previous radiation type models.

Interior Dynamics of Neutral and Charged Black Holes in f(R) Gravity

In this paper, we explore the interior dynamics of neutral and charged black holes in f(R) gravity. We transform f(R) gravity from the Jordan frame into the Einstein frame and simulate scalar collapses in flat, Schwarzschild, and Reissner-Nordström geometries. In simulating scalar collapses in Schwarzschild and Reissner-Nordström geometries, Kruskal and Kruskal-like coordinates are used, respectively, with the presence of f′ and a physical scalar field being taken into account. The dynamics in the vicinities of the central singularity of a Schwarzschild black hole and of the inner horizon of a Reissner-Nordström black hole is examined. Approximate analytic solutions for different types of collapses are partially obtained. The scalar degree of freedom Φ, transformed from f′, plays a similar role as a physical scalar field in general relativity. Regarding the physical scalar field in f(R) case, when dΦ/dt is negative (positive), the physical scalar field is suppressed (magnified) by Φ, where t is the coordinate time. For dark energy f(R) gravity, inside black holes, gravity can easily push f′ to 1. Consequently, the Ricci scalar R becomes singular, and the numerical simulation breaks down. This singularity problem can be avoided by adding an R2 term to the original f(R) function, in which case an infinite Ricci scalar is pushed to regions where f′ is also infinite. On the other hand, in collapse for this combined model, a black hole, including a central singularity, can be formed. Moreover, under certain initial conditions, f′ and R can be pushed to infinity as the central singularity is approached. Therefore, the classical singularity problem, which is present in general relativity, remains in collapse for this combined model.

Spherical collapse inf(R)gravity and the Belinskii-Khalatnikov-Lifshitz conjecture

Spherical scalar collapse in $f(R)$ gravity is studied numerically in double-null coordinates in Einstein frame. Dynamics in the vicinity of the singularity of the formed black hole is examined via mesh refinement and asymptotic analysis. Before the collapse, the scalar degree of freedom ${f}^{\ensuremath{'}}$ is coupled to a physical scalar field, and general relativity is restored. During the collapse, the major energy of the physical scalar field moves to the center. As a result, ${f}^{\ensuremath{'}}$ loses the coupling and becomes light, and gravity transits from general relativity to $f(R)$ gravity. Due to strong gravity from the singularity and the low mass of ${f}^{\ensuremath{'}}$, ${f}^{\ensuremath{'}}$ will cross the minimum of the potential and approach zero. Therefore, the dynamical solution is significantly different from the static solution of the black hole in $f(R)$ gravity---it is not the de Sitter-Schwarzschild solution as one might have expected. ${f}^{\ensuremath{'}}$ tries to suppress the evolution of the physical scalar field, which is a dark energy effect. As the singularity is approached, metric terms are dominant over other terms. The Kasner solution for spherical scalar collapse in $f(R)$ theory is obtained and confirmed by numerical results. These results support the Belinskii-Khalatnikov-Lifshitz conjecture well.

Ultraviolet complete electroweak model without a Higgs particle

An electroweak model with running coupling constants described by an energy dependent entire function is utraviolet complete and avoids unitarity violations for energies above 1 TeV. The action contains no physical scalar fields and no Higgs particle and the physical electroweak model fields are local and satisfy microcausality. The W and Z masses are compatible with a symmetry breaking SU(2)L×U(1)Y $ \rightarrow$ U(1)em , which retains a massless photon. The vertex couplings possess an energy scale $ \Lambda_{W}^{}$ > 1 TeV predicting scattering amplitudes that can be tested at the LHC.

Three dimensional quantum geometry and deformed symmetry

We study a three dimensional noncommutative space emerging in the context of three dimensional Euclidean quantum gravity. Our starting point is the assumption that the isometry group is deformed to the Drinfeld double D(SU(2)). We generalize to the deformed case the construction of E3 as the quotient of its isometry group ISU(2) by SU(2). We show that the algebra of functions on E3 becomes the noncommutative algebra of SU(2) distributions, C(SU(2))∗, endowed with the convolution product. This construction gives the action of ISU(2) on the algebra and allows the determination of plane waves and coordinate functions. In particular, we show the following: (i) plane waves have bounded momenta; (ii) to a given momentum are associated several SU(2) elements leading to an effective description of ϕ∊C(SU(2))∗ in terms of several physical scalar fields on E3; (iii) their product leads to a deformed addition rule of momenta consistent with the bound on the spectrum. We generalize to the noncommutative setting the “local” action for a scalar field. Finally, we obtain, using harmonic analysis, another useful description of the algebra as the direct sum of the algebra of matrices. The algebra of matrices inherits the action of ISU(2): rotations leave the order of the matrices invariant, whereas translations change the order in a way we explicitly determine.

B¯→Xsγin two universal extra dimensions

We calculate the leading order corrections to the $\overline{B}\ensuremath{\rightarrow}{X}_{s}\ensuremath{\gamma}$ decay in the standard model with two large flat universal extra dimensions. We find that the contributions involving the exchange of Kaluza-Klein modes of the physical scalar field ${a}_{(kl)}^{\ifmmode\pm\else\textpm\fi{}}$ depend logarithmically on the ultraviolet cutoff scale $\ensuremath{\Lambda}$. We emphasize that all flavor-changing neutral current transitions suffer from this problem. Although the ultraviolet sensitivity weakens the lower bound on the inverse compactification radius $1/R$ that follows from $\overline{B}\ensuremath{\rightarrow}{X}_{s}\ensuremath{\gamma}$, the constraint remains stronger than any other available direct measurement. After performing a careful study of the potential impact of cutoff and higher-order effects, we find $1/R>650\text{ }\text{ }\mathrm{GeV}$ at 95% confidence level if errors are combined in quadrature. Our limit is at variance with the parameter region $1/R\ensuremath{\lesssim}600\text{ }\text{ }\mathrm{GeV}$ preferred by dark matter constraints.

Bianchi type IX brane-world cosmologies

We shall investigate the asymptotic properties of the Bianchi type IX cosmological model in the Brane-world scenario. The matter content is assumed to be a combination of a perfect fluid and a minimimally coupled scalar field that is restricted to the Brane. A detailed qualitative analysis of the Bianchi type IX braneworld containing a scalar field having an exponential potential is undertaken. It is found that the Brane-Robertson Walker solution is a local source for the expanding Bianchi IX models, and if $k^2<2$ the expanding Bianchi IX models asymptote to the power-law inflationary solution. The only other local sink is the contracting Brane-Robertson Walker solution. An analysis of the Bianchi IX models with a scalar field with a general potential is discussed, and it is shown that in the case of expanding models, for physical scalar field potentials close to the initial singularity, the scalar field is effectively massless, and the solution is approximated by the Brane-Robertson Walker model.

Minimal scalar sector of 3-3-1 models without exotic electric charges

We study the minimal set of Higgs scalars, for models based on the local gauge group $SU(3)_c \otimes SU(3)_L \otimes U(1)_X$ which do not contain particles with exotic electric charges. We show that only two Higgs $SU(3)_L$ triplets are needed in order to properly break the symmetry. The exact tree-level scalar mass matrices resulting from symmetry breaking are calculated at the minimum of the most general scalar potential, and the gauge bosons are obtained, together with their couplings to the physical scalar fields. We show how the scalar sector introduced is enough to produce masses for fermions in a particular model which is an $E_6$ subgroup. By using experimental results we constrain the scale of new physics to be above 1.3 TeV.

Non-local approach in mathematical problems of fluid-structure interaction

Three-dimensional mathematical problems of interaction between elastic and scalar oscillation fields are investigated. An elastic field is to be defined in a bounded inhomogeneous anisotropic body occupying the domain Ω 1 ⊆ R 3 while a physical (acoustic) scalar field is to be defined in the exterior domain Ω 2 = R 3 \Ω 1 which is filled up also by an anisotropic (fluid) medium. These two fields satisfy the governing equations of steady-state oscillations in the corresponding domains together with special kinematic and dynamic transmission conditions on the interface ∂Ω 1 . The problems are studied by the so-called non-local approach, which is the coupling of the boundary integral equation method (in the unbounded domain) and the functional-variational method (in the bounded domain). The uniqueness and existence theorems are proved and the regularity of solutions are established with the help of the corresponding Steklov-Poincare type operators and on the basis of the Garding inequality and the Lax-Milgram theorem. In particular, it is shown that the physical fluid-solid acoustic interaction problem is solvable for arbitrary values of the frequency parameter.

Interaction of Elastic and Scalar Fields

The three-dimensional mathematical problems of the interaction of an elastic and some scalar fields are investigated. It is assumed that the elastic structure under consideration is a bounded homogeneous anisotropic body occupying domain Ω + ⊂ R 3 and the physical scalar field is defined in the exterior domain Q - = R 3 \Ω + . These two fields satisfy the governing equations in the corresponding domains together with the transmission conditions on the interface OΩ + . The problems are studied by the potential method and the existence and uniqueness theorems are proved.

A model of quantum scalar dipole-type X-exotic-boson field at finite temperature

We examine an arbitrary order dimension system of two scalar neutral fields by means of a 1/N expansion method. Using the partial normal-ordering procedure, an application in the study of a light scalar dipole-type field interaction with quarks is proposed. A hypothetical candidate for a (pseudo)-scalar coupling between the quarks inside the bound system would be a light Higgs-like exotic X-particle. The derivative relation of the physical neutral scalar field mass with respect to non-zero temperature is illustrated.

A mapping closure for turbulent scalar mixing using a time-evolving reference field

A methodology for modeling passive scalar mixing in homogeneous turbulence using a new mapping closure approach is developed. The physical scalar field φ(y,t) (y-space coordinate, t time) is mapped using a mapping function, X(t), onto a reference scalar field θ(y,t), whose evolution is known. There are two main differences between the present approach and that of Chen et al. [Phys. Rev. Lett. 63, 2657 (1989)]. In the present approach, the reference field is time evolving and not restricted to a Gaussian. The evolution equation of the mapping function is derived for a general reference field. Gaussian and β-pdf reference fields are investigated. Calculations from both reference fields are compared with the heat conduction simulation (HCS) data of Girimaji (NASA Contract. Rep. 4446, 1992). The limits of validity of the mapping closure approach are discussed.