Narrow Results

In this paper, we perform a comprehensive analysis of conformal symmetries in the generalized Vaidya spacetime and establish several new results. First, a proper conformal Killing vector is shown to exist in the radial direction and interestingly the generalized Vaidya spacetimes with this symmetry are shown to be the subclass of those, which are embeddable in five-dimensional Euclidean space. The general form of the mass function that enables the proper and planar conformal symmetry in the $v$–$r$ plane is also determined. This treatment also includes earlier results. We also consider the gravitational collapse of these spacetimes with proper planar conformal symmetry in the context of cosmic censorship conjecture. We obtain an interesting and novel result that censorship is always obeyed for these spacetimes, and no locally naked central singularity forms as the end state of the continual collapse.

Short distance scaling limits of a class of integrable models on two-dimensional Minkowski space are considered in the algebraic framework of quantum field theory. Making use of the wedge-local quantum fields generating these models, it is shown that massless scaling limit theories exist, and decompose into (twisted) tensor products of chiral, translation-dilation covariant field theories. On the subspace which is generated from the vacuum by the observables localized in finite light ray intervals, this symmetry can be extended to the Möbius group. The structure of the interval-localized algebras in the chiral models is discussed in two explicit examples.

I review a new technique for calculation of higher twist evolution equations in Quantum Chromodynamics.

Kalb–Ramond equations for massive and massless particles are considered in the framework of the Petiau–Duffin–Kemmer formalism. We obtain 10×10 matrices of the relativistic wave equation of the first-order and solutions in the form of density matrix. The canonical and Belinfante energy–momentum tensors are found. We investigate the scale invariance and obtain the conserved dilatation current. It was demonstrated that the conformal symmetry is broken even for massless fields.

We point out a possible mechanism by which the electroweak hierarchy problem can be avoided in the low energy effective quantum field theory. Assuming the existence of a UV complete underlying fundamental theory and treating the cutoff scale Λ of the effective field theory as a real physical scale we argue that the hierarchy problem would be solved if the coefficient in front of quadratic divergences vanished at the scale Λ, and if the effective theory mass parameters fixed at Λ by the fundamental theory were hierarchically smaller than Λ itself. While this mechanism most probably cannot work in the Standard Model if the scale Λ is to be close to the Planck scale, we show that it can work in a minimal extension (Conformal Standard Model) proposed recently for a different implementation of conformal symmetry breaking.

We investigate cylindrically symmetric spacetimes in the context of $f(R)$ gravity. We firstly attain conformal symmetry of the cylindrically symmetric spacetime. We obtain solutions to use features of the conformal symmetry, field equations and their solutions for cylindrically symmetric spacetime filled with various cosmic matters such as vacuum state, perfect fluid, anisotropic fluid, massive scalar field and their combinations. With the vacuum state solutions, we show that source of the spacetime curvature is considered as Casimir effect. Casimir force for given spacetime is found using Wald’s axiomatic analysis. We expose that the Casimir force for Boulware, Hartle–Hawking and Unruh vacuum states could have attractive, repulsive and ineffective features. In the perfect fluid state, we show that matter form of the perfect fluid in given spacetime must only be dark energy. Also, we offer that potential of massive and massless scalar field are developed as an exact solution from the modified field equations. All solutions of field equations for vacuum case, perfect fluid and scalar field give a special $f(R)$ function convenient to $\Lambda$-CDM model. In addition to these solutions, we introduce conformal cylindrical symmetric solutions in the cases of different $f(R)$ models. Finally, geometrical and physical results of the solutions are discussed.

We investigate whether compact stars having Tolman-like interior geometry admit conformal symmetry. Taking anisotropic pressure along the two principal directions within the compact object, we obtain physically relevant quantities such as transverse and radial pressure, density and redshift function. We study the equation of state (EOS) for the matter distribution inside the star. From the relation between pressure and density function of the constituent matter, we explore the nature and properties of the interior matter. The redshift function and compactness parameter are found to be physically reasonable. The matter inside the star satisfies the null, weak and strong energy conditions. Finally, we compare the masses and radii predicted from the model with corresponding values in some observed stars.

We propose a relativistic model of compact star admitting conformal symmetry. Quark matter and baryonic matter which are considered as two different fluids, constitute the star. We define interaction equations between the normal baryonic matter and the quark matter and study the physical situations for repulsive, attractive and zero interaction between the constituent matters. The measured value of the Bag constant is used to explore the spacetime geometry inside the star. From the observed values of the masses of some compact objects, we have obtained theoretical values of the radii. Theoretical values of the radii match well with the previous predictions for such compact objects.

Light-front (LF) quantization of massless fields in two spacetime dimensions is a long-standing and much debated problem. Even though the classical wave-equation is well-documented for almost two centuries, either as problems with initial values in spacetime variables or with initial data on characteristics in light-cone variables, the way to a consistent quantization in both types of frames is still a puzzle in many respects. This is in contrast to the most successful Conformal Field Theoretic (CFT) approach in terms of complex variables $z$, $\bar{z}$ pioneered by Belavin, Polyakov and Zamolodchikov in the ’80s. It is shown here that the 2D-massless canonical quantization in both reference frames is completely consistent provided that quantum fields are treated as Operator-Valued Distributions (OPVD) with Partition of Unity (PU) test functions. We recall first that classical fields have to be considered as distributions (e.g. generalized functions in the Russian literature). Then, a necessary condition on the PU test function follows from the required matching of the classical solutions of the massless differential equations in both types of reference frame. Next we use a mathematical formulation for OPVD, developed in the recent past. Specifically, smooth ${{𝒞}}^{\infty }$ fields are introduced through the convolution operation in the distributional context. Due to the specific behavior of the Fourier-transform of the initial test function, this convolution transform has a well-defined integral in the dual space, whatever the initial choice of the reference frame. The relation to the conformal fields method follows immediately from the transition to Euclidean time and leads directly to explicit calculations of a few correlation functions of the scalar field and its energy–momentum tensor. The LF derivation of the Virasoro algebra is then obtained from the $z$ and $\bar{z}$ expansions of the canonical fields as distributional Laplace-transform in these variables. Finally, the popular and problematic Discretized Light Cone Quantization (DLCQ) method is scrutinized with respect to its zero mode and ultraviolet content as encompassed in the continuum OPVD formulation.

The quantum Casimir condensate of a conformal massive scalar field in a compact Friedmann universe is considered in the static approximation. The Abel–Plana formula is used for renormalization of divergent series in the condensate calculation. A differential relation between the static Casimir energy density and static Casimir condensate is derived.

Heavy $c\bar{c}$ and $b\bar{b}$ quarkonia are considered as systems confined within a hard-wall potential shaped after a linear combination of a cotangent — with a square co-secant function. Wave functions and energy spectra are then obtained in closed forms in solving by the Nikiforov–Uvarov method the associated radial Schrödinger equation in the presence of a centrifugal term. The interest in this potential is that in one parametrization, it can account for a conformal symmetry of the strong interaction, and in another for its perturbation, a reason for which we here employ it to study status of conformal symmetry in the heavy flavor sector. The resulting predictions on heavy quarkonia mass spectra and root mean square radii are compared with the available experimental data, as well as with predictions by other theoretical approaches. We observe that a relatively small conformal symmetry perturbing term in the potential suffices to achieve good agreement with data.

In this paper, we generalize our previous model (arXiv:1705.09331), on a hidden conformal symmetry of smooth braneworld scenarios, to the case with two real scalar fields non-minimally coupled to gravity. The gauge condition reduces the action of the system to the action where gravity minimally couples to one of the scalar fields, plus a cosmological constant. We show that, depending on the internal symmetry of the scalar fields, the two possibilities, SO(2) or SO(1, 1), emerge. In the SO(2) case, we get a ghost-like scalar field action, which can describe two models — Standing Wave and Sine-Gordon smooth braneworlds. For the SO(1, 1) case we get the standard sign for the kinetic part of the scalar field. By breaking the SO(1, 1) symmetry (but keeping the conformal one) we are able to get two Randall–Sundrum models, with a non-minimal coupling and with a scalar field having hyperbolic potential. We conclude that this method can be seen as a solution-generating technique and a natural way to introduce nontrivial scalar fields that can provide smooth braneworld models.

In this paper, conformal symmetric Freidmann–Robertson–Walker (FRW) universe with perfect fluid in the framework of $f(R,T)$ gravitational theory is investigated. Firstly, field equations of FRW universe with perfect fluid are obtained for $f(R,T)=R+h(T)$ modified theory of gravity. The field equations of the model have been revised to understand physical nature between matter and geometry by means of conformal symmetry in $f(R,T)$ gravitational theory. The exact solutions of conformal FRW universe with perfect fluid are attained for matter part of the $f(R,T)$ model in the case of $h(T)=\lambda T$. The $f(R,T)$ gravitational theory is one of the acceptable modifications of General Relativity (GR) in order to expound cosmic acceleration of the universe with no needing any exotic component. Nevertheless, the obtained model indicates exotic matter distribution for the current selection of arbitrary constants. Also, different value selections of arbitrary constants for the obtained model are able to predicate expanding or contracting universe with zero deceleration. Besides, it is shown that the FRW universe under the influence of the conformal Killing vector preserves to isotropic nature. Energy conditions are investigated. Also, it is shown that the constructed model satisfies strong energy condition (SEC) in all cases.

Anomalous features of models with nonlinear symmetry realization are addressed. It is shown that such models can have anomalous amplitudes breaking of its original symmetry realization. An illustrative example of a simple models with a nonlinear conformal symmetry realization is given. It is argued that the effective action obtained via nonlinear symmetry realization should be used to obtain an anomaly-induced action which is to drive the low-energy dynamics.

In this paper, we elucidate the relation between the restricted Weyl symmetry and spontaneous symmetry breakdown of conformal symmetry. Using a scalar–tensor gravity, we show that the restricted Weyl symmetry leads to spontaneous symmetry breakdown of a global scale symmetry when the vacuum expectation value of a scalar field takes a nonzero value. It is then shown that this spontaneous symmetry breakdown induces spontaneous symmetry breakdown of special conformal symmetry in a flat Minkowski spacetime, but the resultant Nambu–Goldstone boson is not an independent physical mode but expressed in terms of the derivative of the dilaton which is the Nambu–Goldstone boson of the global scale symmetry. In other words, the theories which are invariant under the general coordinate transformation and the restricted Weyl transformation exhibit a Nambu–Goldstone phase where both special conformal transformation and dilatation are spontaneously broken while preserving the Poincaré symmetry.

In this paper, we review how the “cusp” predicted in the nuclear symmetry energy generated by a topology change at density $n_{1/2}\gtrsim 2n_0$ can have a surprising consequence, so far unrecognized in nuclear physics and astrophysics communities, on the structure of dense compact-star matter. The topology change translated into nuclear EFT with “effective” QCD degrees of freedom encoded in hidden local and scale symmetries predicts an EoS that is soft below and stiff above$n\gtrsim n_{1/2}$, and yields the properties of neutron stars with no tension with all the astrophysical observations available up to date. Furthermore it describes the interior core of the massive stars populated by fractionally charged quasi-fermions that are neither baryonic nor quarkonic. It is argued that the cusp “buried” in the symmetry energy resulting from strong correlations with hidden heavy degrees of freedom leads, at $n\gtrsim n_{1/2}$, to a “pseudo-conformal” sound speed, $v_{\mathrm{\text{pcs}}}^2/c^2\approx 1/3$, converged from below at $n_{1/2}$. It is not conformal since the trace of energy–momentum tensor is not zero even in the chiral limit. It reflects an emergent scale symmetry. This observation with the topology change implies that the quantities accurately measured at $\sim n_0$ cannot give a qualitatively stringent constraint for what takes place at the core density of compact stars $\sim (3\text{–}7)n_0$. This is because there intervenes a change of degrees of freedom in the effective field theory. We discuss the implication of this on the recent PREX-II “dilemma” in the measured skin thickness of ${}^{208}\mathrm{\text{Pb}}$.

In this paper, we introduce the formalism to examine the impact of the dark scalar sector to the conformal and the electroweak symmetries breaking in the sense of formation of the scalar boson star (BS). The BS is presented by the local scalar field containing the Higgs boson field and the scalar dilaton field in the conformal field theory. We study in detail the modification of the Higgs quartic coupling away from its Standard Model (SM) value within the influence of the dark sector. We show that the repulsive self-interactions and the flatness degree in the dark scalar sector can prevent an instability and the destruction of the BS. We have estimated the rate of the deviation from the SM with production of leptonic pairs due to decays of dilatons and dark photons emerged because of the BS instability. The lifetime, the maximal mass and the density of the BS, the average minimal distance between the stars are estimated. The effects of new physics should be visible at the HL-LHC, FCC-hh accompanied by the current LHC and the cosmological data.

In this study, we explore the behavior of a Morris–Thorne wormhole under the influence of a Ricci soliton vector field. We derive the expressions for the four components of the vector field in this context and determine the corresponding shape function. Our analysis shows that the wormhole solution satisfies all the criteria for a traversable wormhole. Notably, we identify a negative trend in the null energy condition near the wormhole’s throat. To provide further insight, we present an embedding diagram depicting the wormhole’s geometry. Additionally, we evaluate its stability using the Tolman–Oppenheimer–Volkoff (TOV) equation and calculate the required exotic matter through the Volume Integral Quantifier.

The universal behavior of Hawking radiation is originated in the conformal symmetries of matter fields near the black hole horizon. We explain the origin of this universality based on (1) the gravitational anomaly and its higher-spin generalizations and (2) conformal transformation properties of fluxes.

In contrast to the folklore that Technicolor (TC) is a "Higgsless theory", we shall discuss existence of a composite Higgs boson, Techni-Dilaton (TD), a pseudo-Nambu-Goldstone boson of the scale invariance in the Scale-invariant/Walking/Conformal TC (SWC TC) which generates a large anomalous dimension γ_m ≃ 1 in a wide region from the dynamical mass of the techni-fermion all the way up to the intrinsic scale Λ_TC of the SWC TC (analogue of Λ_QCD), where Λ_TC is taken typically as the scale of the Extended TC scale Λ_ETC: Λ_TC ≃ Λ_ETC ~ 10³TeV (≫ m). All the techni-hadrons have mass on the same order , which in SWC TC is extremely smaller than the intrinsic scale Λ_TC ≃ Λ_ETC, in sharp contrast to QCD where both are of the same order. The mass of TD arises from the non-perturbative scale anomaly associated with the techni-fermion mass generation and is typically 500-600 GeV, even smaller than other techni-hadrons of the same order of , in another contrast to QCD which is believed to have no scalar bound state lighter than other hadrons. We discuss the TD mass in various methods, Gauged NJL model via ladder Schwinger-Dyson (SD) equation, straightforward calculations in the ladder SD/ Bethe-Salpeter equation, and the holographic approach including techni-gluon condensate. The TD may be discovered in LHC.