Self-coupling Constant Research Articles

Criterion of perturbativity with the mass-dependent beta function in extended Higgs models

In order to realize an electroweak first-order phase transition, a category of extended Higgs models with relatively large self-coupling constants is often considered. In such a scenario, the running coupling constants can blow up at an energy scale much below the Planck scale. To clarify the allowed parameter space of the model, it is important to evaluate the scale where perturbative calculation breaks down. In the renormalization group equation analysis using the mass-independent renormalization scheme, we need a matching condition to connect the low energy theory and the high energy theory. Consequently, the analysis depends on the details of the matching condition. On the other hand, an analysis with the mass-dependent beta function can be performed in a simpler way because the threshold effect is automatically included in the beta function. In this paper, using the mass-dependent beta function, we discuss the application limit of perturbative calculations at the one-loop level. First, we explain the essence of our method and compare our results with those based on the mass-independent beta function in a toy model with two complex scalar fields. We then apply our method to a more realistic model, i.e., the inert doublet model. We find that, in our method, in which the threshold effect is automatically included, the energy scale where the perturbative calculation breaks down can be higher than the one using the mass-independent beta function, especially when the blowup scale is relatively low. Published by the American Physical Society 2024

Excited Abelian-Higgs vortices: Decay rate and radiation emission

The evolution of 1 vortices when their massive bound mode is excited is investigated in detail (both analytically and numerically) in the Abelian-Higgs model for different ranges of the self-coupling constant. The dependence of the spectrum of the 1 vortex fluctuation operator on the model parameter is discussed initially. A perturbative approach is employed to study the radiation emission in both the scalar and the vector channels. Our findings reveal that the oscillating initial configuration of the 1 vortex radiates at a frequency twice that of the internal mode. Through energy conservation considerations, we derive the decay law of the massive mode. Finally, these analytical results are compared with numerical simulations in field theory. Published by the American Physical Society 2024

Exploring the Distribution and Impact of Bosonic Dark Matter in Neutron Stars

The presence of dark matter (DM) within neutron stars (NSs) can be introduced by different accumulation scenarios in which DM and baryonic matter (BM) may interact only through the gravitational force. In this work, we consider asymmetric self-interacting bosonic DM, which can reside as a dense core inside the NS or form an extended halo around it. It is seen that depending on the boson mass (mχ), self-coupling constant (λ) and DM fraction (Fχ), the maximum mass, radius and tidal deformability of NSs with DM admixture will be altered significantly. The impact of DM causes some modifications in the observable features induced solely by the BM component. Here, we focus on the widely used nuclear matter equation of state (EoS) called DD2 for describing NS matter. We show that by involving DM in NSs, the corresponding observational parameters will be changed to be consistent with the latest multi-messenger observations of NSs. It is seen that for mχ≳200 MeV and λ≲2π, DM-admixed NSs with 4%≲Fχ≲20% are consistent with the maximum mass and tidal deformability constraints.

Application of Particle Transformer to quark flavor tagging in the ILC project

International Linear Collider (ILC) is a next-generation e+e− linear collider to explore Beyond-Standard-Models by precise measurements of Higgs bosons. Jet flavor tagging plays a vital role in the ILC project by identification of H → bb¯, cc¯, gg, ss¯ to measure Higgs coupling constants and of HH → bb¯bb¯ and bb¯WW which are the main channels to measure the Higgs self-coupling constant. Jet flavor tagging relies on a large amount of jet information such as particle momenta, energies, and impact parameters, obtained from trajectories of particles within a jet. Since jet flavor tagging is a classification task based on massive amounts of information, machine learning techniques have been utilized for faster and more efficient analysis for the last several decades. Particle Transformer (ParT) is a machine learning model based on Transformer architecture developed for jet analysis, including jet flavor tagging. In this study, we apply ParT to ILD full simulation data to improve the efficiency of jet flavor tagging. Our research focused on evaluating the performance of ParT compared to that of the previously used flavor tagging software, LCFIPlus. We will also report the status of the performance of strange tagging on ILD full simulation dataset using ParT, which can be applied to the analysis of Higgs-strange coupling.

Bosonic dark matter in neutron stars and its effect on gravitational wave signal

We study an impact of self-interacting bosonic dark matter (DM) on various observable properties of neutron stars (NSs). The analysis is performed for asymmetric DM with masses from few MeV to GeV, the self-coupling constant of order $\mathcal{O}(1)$ and various DM fractions. Allowing a mixture between DM and baryonic matter, the formation of a dense DM core or an extended dark halo have been explored. We find that both distribution regimes crucially depend on the mass and fraction of DM for sub-GeV boson masses in the strong coupling regime. From the combined analysis of the mass-radius relation and the tidal deformability of compact stars including bosonic DM, we set a stringent constraint on DM fraction. We conclude that observations of 2$M_{\odot}$ NSs together with $\Lambda_{1.4}\leq580$ constraint, set by LIGO/Virgo Collaboration, favour sub-GeV DM particles with low fractions below $\sim 5 \%$.

Boson stars and their radial oscillations

We review the derivation of the pulsations equations for spherically symmetric boson stars and then make a thorough study of the radial oscillation frequencies for the fundamental and first excited modes. We do this for self-interacting boson stars and consider a range of values for the self-coupling constant. We also numerically evolve boson stars and Fourier transform the dynamic solutions. The Fourier transform gives an independent computation of the radial oscillation frequencies and allows us to verify our results obtained from the pulsation equations. We find excellent agreement between the two methods.

Higgs Inflation with four-form couplings

We consider a new inflationary model in which an antisymmetric tensor field A νρσ and its four-form field strength F μνρσ = 4∂[μ A νρσ] are coupled to the scalar sector of the standard model and to the Ricci scalar . The four-form field induces modifications to the Higgs self-coupling constant, the cosmological constant, and the non-minimal coupling constant, which results in the modification to the inflaton potential. We also show that there is no need for the Higgs-gravity coupling in the presence of four-form gravity interaction, but still can produce the right amount of density perturbation for inflation.

Nonlinear radion interactions

We consider the Randall–Sundrum model with two branes in which the fields of the Standard Model are localized on the brane with negative tension and the gravitational field and an additional stabilizing scalar Goldberg–Wise field propagate in the space between the branes. We construct a Lagrangian for scalar fluctuations of the gravitational and scalar fields against the background solution. We obtain an effective four-dimensional Lagrangian describing nonlinear self-coupling terms of the scalar radion field in a polynomial approximation up to the fourth order and also nonlinear terms of the coupling of the radion and Standard Model fields. We estimate possible values of the self-coupling constant.

Cosmological time evolution of the Higgs mass and gravitational waves

We point out that gravitational wave detectors such as LISA have the potential of probing a cosmological time evolution of the Higgs boson self-coupling constant [Formula: see text] and thus the Higgs boson’s mass [Formula: see text]. The phase transition of the Standard Model could have been a first order one if the Higgs mass was below 72 GeV at a temperature [Formula: see text] GeV. Gravitational waves could thus have been produced during the electroweak phase transition. A discovery by LISA of a stochastic background of gravitational waves with a characteristic frequency [Formula: see text] Hz could be interpreted as a sign that the Higgs boson self-coupling constant was smaller in the past. This interpretation would be particularly tempting if the Large Hadron Collider did not discover any physics beyond the Standard Model by the time such waves are seen. The same mechanism could also account for baryogenesis.

Effective Mass of Radion via GW Mechanism with a Non-Minimally Coupled Bulk Scalar Field

In the Randall-Sundrum braneworld scenario via the Goldberger-Wise mechanism, the effective mass of 4D radion, where the bulk scalar field is coupled to 5D gravity, has been investigated in two different case of the self-coupling constants, infinite and finite cases. It is shown that in the finite case, the modulus parameter should be greater than the finite coupling constants.

Spinor Field Nonlinearity and Space-Time Geometry

Within the scope of Bianchi type VI,VI0,V, III, I, LRSBI and FRW cosmological models we have studied the role of nonlinear spinor field on the evolution of the Universe and the spinor field itself. It was found that due to the presence of non-trivial non-diagonal components of the energy-momentum tensor of the spinor field in the anisotropic space-time, there occur some severe restrictions both on the metric functions and on the components of the spinor field. In this report we have considered a polynomial nonlinearity which is a function of invariants constructed from the bilinear spinor forms. It is found that in case of a Bianchi type-VI space-time, depending of the sign of self-coupling constants, the model allows either late time acceleration or oscillatory mode of evolution. In case of a Bianchi VI0 type space-time due to the specific behavior of the spinor field we have two different scenarios. In one case the invariants constructed from bilinear spinor forms become trivial, thus giving rise to a massless and linear spinor field Lagrangian. This case is equivalent to the vacuum solution of the Bianchi VI0 type space-time. The second case allows non-vanishing massive and nonlinear terms and depending on the sign of coupling constants gives rise to accelerating mode of expansion or the one that after obtaining some maximum value contracts and ends in big crunch, consequently generating space-time singularity. In case of a Bianchi type-V model there occur two possibilities. In one case we found that the metric functions are similar to each other. In this case the Universe expands with acceleration if the self-coupling constant is taken to be a positive one, whereas a negative coupling constant gives rise to a cyclic or periodic solution. In the second case the spinor mass and the spinor field nonlinearity vanish and the Universe expands linearly in time. In case of a Bianchi type-III model the space-time remains locally rotationally symmetric all the time, though the isotropy of space-time can be attained for a large proportionality constant. As far as evolution is concerned, depending on the sign of coupling constant the model allows both accelerated and oscillatory mode of expansion. A negative coupling constant leads to an oscillatory mode of expansion, whereas a positive coupling constant generates expanding Universe with late time acceleration. Both deceleration parameter and EoS parameter in this case vary with time and are in agreement with modern concept of space-time evolution. In case of a Bianchi type-I space-time the non-diagonal components lead to three different possibilities. In case of a full BI space-time we find that the spinor field nonlinearity and the massive term vanish, hence the spinor field Lagrangian becomes massless and linear. In two other cases the space-time evolves into either LRSBI or FRW Universe. If we consider a locally rotationally symmetric BI(LRSBI) model, neither the mass term nor the spinor field nonlinearity vanishes. In this case depending on the sign of coupling constant we have either late time accelerated mode of expansion or oscillatory mode of evolution. In this case for an expanding Universe we have asymptotical isotropization. Finally, in case of a FRW model neither the mass term nor the spinor field nonlinearity vanishes. Like in LRSBI case we have either late time acceleration or cyclic mode of evolution. These findings allow us to conclude that the spinor field is very sensitive to the gravitational one.

A novel way to determine the scale of inflation

We show that in the Feebly Interacting Massive Particle (FIMP) model of Dark Matter (DM), one may express the inflationary energy scale H* as a function of three otherwise unrelated quantities, the DM isocurvature perturbation amplitude, its mass and its self-coupling constant, independently of the tensor-to-scalar ratio. The FIMP model assumes that there exists a real scalar particle that alone constitutes the DM content of the Universe and couples to the Standard Model via a Higgs portal. We consider carefully the various astrophysical, cosmological and model constraints, accounting also for variations in inflationary dynamics and the reheating history, to derive a robust estimate for H* that is confined to a relatively narrow range. We point out that, within the context of the FIMP DM model, one may thus determine H* reliably even in the absence of observable tensor perturbations.

Hyperbolic deformation of a gauge field theory and the hierarchy problem

The problem of the gauge hierarchy is brought up in a hypercomplex scheme for a [Formula: see text] field theory; in such a scheme, a compact gauge group is deformed through a [Formula: see text]-parameter that varies along a noncompact internal direction, transverse to the [Formula: see text] compact one, and thus an additional [Formula: see text] gauge symmetry is incorporated. This transverse direction can be understood as an extra internal dimension, which will control the spontaneous symmetry breakdown, and will allow us to establish a mass hierarchy. In this mechanism, there is no brane separation to be estabilized as in the braneworld paradigm, however, a different kind of fine-tuning is needed in order to generate the wished electroweak/Planck hierarchy. By analyzing the effective self-interactions and mass terms of the theory, an interesting duality is revealed between the real and hybrid parts of the effective potential. This duality relates the weak and strong self-interaction regimes of the theory, due to the fact that both mass terms and self-coupling constants appear as one-parameter flows in [Formula: see text]. Additionally, the [Formula: see text]-deformation will establish a flow for the electromagnetic coupling that mimics the renormalization group flow for the charge in QED.

Spinor field with polynomial nonlinearity in LRS Bianchi type-I space–time

Within the scope of the locally rotationally symmetric (LRS) Bianchi type-I cosmological model the role of spinor field on the evolution of the Universe is investigated. In doing so, we have considered a polynomial type of nonlinearity. It is found that, depending on the sign of the self-coupling constant, the model allows either an accelerated mode of expansion or an oscillatory mode of evolution. While the non-diagonal components of the energy–momentum tensor of the spinor field in the case of a full Bianchi type-I model lead to the vanishing mass and nonlinear term in the spinor field Lagrangian, in the case of an LRS Bianchi type-I model neither the mass term nor the nonlinear term of the spinor field vanish.

Transition between monopole and antimonopole for electrically charged monopole–antimonopole chain system of solutions

The dependence of physical properties of the electrically charged monopole–antimonopole pair (MAP) solutions in the Higgs self-coupling constant is previously investigated. In this paper we study the three-poles monopole–antimonopole chain (MAC) solutions. The study includes ϕ-winding number n=2,3, and 4. For the case of n=2, no bifurcation and geometrical transition is detected for the interval of the study. For the case of n=3, two geometrical transitions happen along the fundamental solution. Also two bifurcations and one joining point is detected for the interval of study. The case of n=4 includes one bifurcation. There is also a geometrical transition along the fundamental solution and two transitions along the Higher energy bifurcating branch. This study implies that during some specific kind of geometrical transition, a magnetic and electric charge transition occurs for the pole which is located at the origin.

Calculation of Higgs Self-Coupling Constant for One-Loop and Two-Loop Effective Potentials and Their Perturbative Validity

Although the Standard Model has been very successful in explaining the present data, it is unable to express the value of Higgs self coupling constant. It is a free parameter of the theory. Recently a Higgs like particle is reported to be discovered at CMS and ATLAS experiments at CERN LHC with a mass of about 125 GeV. The purpose of this paper is to calculate the value of Higgs self coupling constant in the Standard Model for one and two-loops Higgs potential. Considering the value of Higgs mass as 125 GeV we obtain the value of Higgs self coupling constant as 0.1373 for both one and two-loops Higgs potential. We also find that the condition for perturbative validity given by Miller is satisfied, when the Higgs mass is calculated perturbatively from the effective potential given by the massless φ^4 theory at one and two-loop level.

Trinification phenomenology and the structure of Higgs bosons

The extension of the Standard Model to $SU(3)_L \times SU(3)_R \times SU(3)_C$ (the trinification group) augmented by the $ SO(3)_G $ flavor group is considered. In our phenomenological treatment partly known and partly proposed vacuum expectation values of the scalar Higgs fields play a dominant role. All Higgs fields are taken to be flavor singlets, all flavon fields trinification singlets. We need two flavor (generation) matrices. One determines the mass hierarchy of all fermions, the second one is responsible for all mixings including the CP-violating phase in the CKM matrix. The mixing with higher states contained in the group representation provides for an understanding of the difference between the up quark and the down quark spectrum. There is a close connection between charged and neutral fermions. An inverted neutrino hierarchy is predicted. Examples for the tree-level potential of the Higgs fields are given. To obtain an acceptable spectrum of scalar states, the construction of the potential requires the combination of matrix fields that differ with respect to fermion couplings and flavor-changing properties. As a consequence bosons with fermiophobic components or, alternatively, flavor-changing components are predicted in this model. Nevertheless, the Higgs boson at 125 GeV is very little different from the Standard Model Higgs boson in its couplings to fermions but may have self-coupling constants larger by a factor 2.

Electrically charged one-and-a-half monopole solution

Recently, we have discussed the coexistence of a finite energy one-half monopole and a ’t Hooft–Polyakov monopole of opposite magnetic charges. In this paper, we would like to introduce electric charge into this new monopoles configuration, thus creating a one-and-a-half dyon. This new dyon possesses finite energy, magnetic dipole moment, and angular momentum and is able to precess in the presence of an external magnetic field. Similar to the other dyon solutions, when the Higgs self-coupling constant, \(\lambda \), is nonvanishing, this new dyon solution possesses critical electric charge, total energy, magnetic dipole moment, and dipole separation as the electric charge parameter, \(\eta \), approaches 1. The electric charge and total energy increase with \(\eta \) to maximum critical values as \(\eta \rightarrow 1\) for all nonvanishing \(\lambda \). However, the magnetic dipole moment decreases with \(\eta \) when \(\lambda \ge 0.1\) and the dipole separation decreases with \(\eta \) when \(\lambda \ge 1\) to minimum critical values as \(\eta \rightarrow 1\).

Quadratic chaotic inflation from Higgs inflation

Stimulated with the recent discovery of B-mode by BICEP2, we discuss the relation between a Higgs inflation and a chaotic inflation with quadratic potential. Starting with a generalized Higgs inflation model, we derive a condition for obtaining the quadratic chaotic inflation. It is shown that the running of the Higgs self-coupling constant in the Jordan frame plays a decisive role when the generalized Higgs inflation model coincides with the Higgs inflation model in a small-field limit.

CHO DECOMPOSITION OF ONE-HALF INTEGER MONOPOLES SOLUTIONS

We performed the Cho decomposition of the SU(2) Yang–Mills–Higgs gauge potentials of the finite energy (1) one-half monopole solution and (2) the one and a half monopoles solution into Abelian and non-Abelian components. We found that the semi-infinite string singularity in the gauge potentials is a contribution from the Higgs field of the one-half monopole in both of the solutions. The non-Abelian components of the gauge potentials are able to remove the point singularity of the Abelian components of the 't Hooft–Polyakov monopole but not the string singularity of the one-half monopole which is topological in nature. Hence the total energy of a one monopole is infinite in the Maxwell electromagnetic theory but the total energy of a one-half monopole is finite. By analyzing the magnetic fields and the gauge covariant derivatives of the Higgs field, we are able to conclude that both the one-half integer monopoles solutions are indeed non-BPS even in the limit of vanishing Higgs self-coupling constant.