The ℋolographic 𝒩aturalness (ℋ𝒩) is a new paradigm towards an explanation of the Cosmological Constant (CC) and the Higgs Hierarchy (HH) in the Universe. Motivated by the Holographic Principle, and inspired by the (A)dS/CFT correspondence, we elaborate on the possibility and on the cosmological consequences of a fundamental intrinsic disorder and temperature in vacuo. We postulate that the zero vacuum

From the assumption that the slow-roll parameter 𝜖 has a Lorentzian form as a function of the e-folds number N, a successful model of a quintessential inflation is obtained. The form corresponds to the vacuum energy both in the inflationary and in the dark energy epochs. The form satisfies the condition to climb from small values of 𝜖 to 1 at the end of the inflationary epoch. At the late universe

We consider a class of helical phase inflation models from the N =1 supergravity where the phase component of a complex field acts as an inflaton. This class of models avoids the eta problem in supergravity inflation due to the phase monodromy of the superpotential. We study the inflationary predictions of this class of models in the context of both standard and large extra dimensional brane cosmology

Recent studies with SDSS have shown that a statistically significant non-zero mutual information between morphology and environment persists up to several tens of Mpc, which awaits an explanation. Galaxies in different environments acquire their stellar mass through accretion and merger and the stellar mass function of galaxies is known to depend on both environment and morphology. Naturally, stellar

An ultralight scalar field is a candidate for the dark matter. The ultralight scalar dark matter with mass around 10 −23 eV induces oscillations of the pulse arrival time in the sensitive frequency range of the pulsar timing arrays. We search for the ultralight scalar dark matter using the North American Nanohertz Observatory for Gravitational Waves 11-year Data Set. We give the 95% confidence upper

We study the stochastic gravitational wave (GW) background induced by the primordial scalar perturbation with the spectrum having a lognormal peak of width Δ at k = k * . We derive an analytical formula for the GW spectrum Ω GW for both narrow (Δ ##IMG## [https://ej.iop.org/icons/Entities/ll.gif] {ll} 1) and broad (Δ ##IMG## [https://ej.iop.org/icons/Entities/gtrsim.gif] {gtrsim} 1) peaks. In the narrow-peak

We compute the energy spectrum of photons {and neutrinos} produced by the unwinding of a scaling distribution of cosmic textures, and discuss the implications for the spectrum of high energy cosmic rays, and for CMB spectral distortions. Textures lead to a contribution to the photon flux which scales as E 3 F ( E) ~ E 3/2 . Hence, the tightest constraints on the texture model come from the highest

We consider three fundamental issues in quantum gravity: (a) the black hole information paradox (b) the unboundedness of entropy that can be stored inside a black hole horizon (c) the relation between the black hole horizon and the cosmological horizon. With help from the small corrections theorem, we convert each of these issues into a sharp conflict. We then argue that all three conflicts can be

We propose a modified gravity theory that propagates only two local gravitational degrees of freedom and that does not have an Einstein frame. According to the classification in [2], this is a type-II minimally modified gravity theory. The theory is characterized by the gravitational constant G N and a function V ( ##IMG## [https://ej.iop.org/icons/Entities/phi.gif] {phi} ) of a non-dynamical auxiliary

We revisit the cosmological history in the presence of light moduli by including possible thermal effects in the scalar potential. The well known cosmological moduli problem regards initial energy stored in the moduli due to a misalignment from its final position during inflation. We show that finite temperature corrections to the scalar potential, in general, induce similar effects and these are likely

Recently, a non-trivial 4 D Einstein-Gauss-Bonnet (EGB) theory of gravity, by rescaling the GB coupling parameter as α/( D −4), was formulated in [1], which bypasses Lovelock's theorem and avoids Ostrogradsky instability. The theory admits a static spherically symmetric black hole, unlike 5 D EGB or general relativity counterpart, which can have both Cauchy and event horizons. We generalize previous

Neutron stars provide a cosmic laboratory to study the nature of dark matter particles and their interactions. Dark matter can be captured by neutron stars via scattering, where kinetic energy is transferred to the star. This can have a number of observational consequences, such as the heating of old neutron stars to infra-red temperatures. Previous treatments of the capture process have employed various

Ultra-light Dark Matter (ULDM) models are suitable candidates for the cosmological Dark Matter that may leave characteristic imprints in many observables. Among other probes, signatures of ULDM can be searched for in pulsar timing data. In this work we describe the effects of spin-2 ULDM on pulsar timing arrays, extending previous results on lower spins. Spin-2 ULDM is universally coupled to standard

The space of inflationary models is vast, containing wide varieties of mechanisms, symmetries, and spectra of particles. Consequently, the space of observational signatures is similarly complex. Hence, it is natural to look for boundaries of the space of models and their signatures. In this paper, we explore the possible symmetries associated with the primordial cosmological perturbations and their

Standard cosmology predicts that prior to matter-radiation equality about 41% of the energy density was in free-streaming neutrinos. In many beyond Standard Model scenarios, however, the amount and free-streaming nature of this component is modified. For example, this occurs in models with new neutrino self-interactions or an additional dark sector with interacting light particles. We consider several

We propose a holographic map between Einstein gravity coupled to matter in a de Sitter background and large N quantum mechanics of a system of spins. Holography maps a spin model with a finite-dimensional Hilbert space defined on a version of the stretched horizon into bulk gravitational dynamics. The full Hamiltonian of the spin model contains a nonlocal piece which generates chaotic dynamics, widely

Bimetric theory describes a massless and a massive spin-2 field with fully non-linear (self-)interactions. It has a rich phenomenology and has been successfully tested with several data sets. However, the observational constraints have not been combined in a consistent framework, yet. We propose a parametrization of bimetric solutions in terms of the effective cosmological constant Λ and the mass m

Axion-like particles (ALPs), predicted in theories beyond the Standard Model, can have observational effects on the transparency of the Universe to γ rays in the presence of magnetic fields. In this work, we search for effects compatible with the existence of ALPs with 80 months of data from the Fermi Large Area Telescope, by comparing the distributions of observed highest energy photons from sources

Searching for violations of the no-hair theorem (NHT) is a powerful way to test gravity, and more generally fundamental physics, particularly with regards to the existence of additional scalar fields. The first observation of a black hole (BH) shadow by the Event Horizon Telescope (EHT) has opened a new direct window onto tests of gravity in the strong-field regime, including probes of violations of

The LIGO/Virgo collaboration have by now detected the mergers of ten black hole binaries via the emission of gravitational radiation. The hypothesis that these black holes have formed during the cosmic QCD epoch and make up all of the cosmic dark matter, has been rejected by many authors reasoning that, among other constraints, primordial black hole (PBH) dark matter would lead to orders of magnitude

We present predictions for the interactions of energetic neutrinos with matter as they propagate through Earth towards large-volume detectors. Our results are based on state-of-the-art calculations of the high-energy neutrino-matter interaction cross-sections, which we have implemented in the HEDIS module of GENIE . In addition to the dominant interaction process, deep inelastic scattering off quarks

The discoveries of LIGO/Virgo black holes in recent years have revitalized the study of primordial black holes. In this work we investigate a mechanism where primordial black holes are formed by vacuum bubbles that randomly nucleate during inflation through quantum tunneling. After inflation, these bubbles typically run into the ambient radiation fluid with a large Lorentz factor. In our previous work

Northwest Africa (NWA) 8709 is a rare example of a type 3 ordinary chondrite melt breccia and provides critical information for the shock compaction histories of chondrites. An L3 protolith for NWA 8709 is inferred on the basis of oxygen isotope composition, elemental composition, diverse mineral chemistry, and overall texture. NWA 8709 is among the most strongly shocked type 3 chondrites known, and

We discuss a new formalism for constructing a nonrelativistic (NR) theory in curved background. Named as galilean gauge theory, it is based on gauging the global galilean symmetry. It provides a systematic algorithm for obtaining the covariant curved spacetime generalisation of any NR theory defined in flat spacetime. The resulting background is just the Newton–Cartan manifold. The example of NR free

We present a detailed analysis of a rotating black hole surrounded by “quintessence.” This solution represents a fluid with a constant equation of state, w, which can for example describe an effective warm dark matter fluid around a black hole. We clarify the conditions for the existence of such a solution and study its structure by analyzing the existence of horizons as well as the extremal case.

In 1911, Einstein proposed that light bending by the Sun’s gravitational field could be measured during a total solar eclipse. The first opportunity in which this measurement would be tried was during the total solar eclipse of October 10, 1912. We report about the expeditions sent to Brazil to observe this eclipse, including the one from the Córdoba Observatory, from Argentina, which aimed to measure

The Hadamard parametrix is a representation of the short-distance singularity structure of the Feynman Green’s function for a quantum field on a curved spacetime background. Subtracting these divergent terms regularizes the Feynman Green’s function and enables the computation of renormalized expectation values of observables. We study the Hadamard parametrix for a charged, massive, complex scalar field

In this paper, we examine the emergence of conserved charges on the horizon of a particular class of extremal nondilatonic black p-branes (which reduce to extremal dilatonic black holes in D=4 dimensions upon toroidal compactification) in the presence of a probe massless scalar field in the bulk. This result is achieved by writing the black p-brane geometry in a Gaussian null coordinate system which

Celebrating the centennial of its first experimental test, the theory of General Relativity (GR) has successfully and consistently passed all subsequent tests with flying colors. It is expected, however, that at certain scales new physics, in particular, in the form of quantum corrections, will emerge, changing some of the predictions of GR, which is a classical theory. In this respect, black holes

We analyze the scalar radiation emitted by a source in a circular geodesic orbit around a spherically symmetric black hole. The black hole (BH) spacetime considered is quite general, in the sense that it encompasses the solutions of Schwarzschild and Reissner–Nordström, and also the Bardeen solution of a regular BH. We use the framework of quantum field theory in curved spaces to compute the one-particle

We generalize the algorithm that establishes the correspondence between metric-affine Eddington-inspired Born-Infeld (EiBI) gravity and General Relativity (GR) to any bosonic matter sector. Along the way, a polished version of the proof of existence of a metric compatible frame associated to any metric-affine Ricci-Based Gravity (RBG) is presented. Particular attention is given to the problem of generating

General Relativity (GR) and the Standard Model (SM) of particle physics are two enormously successful frameworks for our understanding the fundamental laws of nature. However, these theoretical schemes are widely disconnected, logically independent and unrelated in scope. Yet, GR and SM at some point must intersect, producing claims about phenomena that should be reconciled. Be it as it may, both schemes

Massive bosons in the vicinity of Kerr–Newman black holes can form pure bound states when their phase angular velocity fulfills the synchronization condition, i.e. at the threshold of superradiance. The presence of these stationary clouds at the linear level is intimately linked to the existence of Kerr black holes with synchronized hair at the nonlinear level. These configurations are very similar

Tidal forces produced by black holes are an important result of General Relativity related to the spacetime curvature tensor. Among the astrophysical implications of tidal forces, the tidal disruption events stand out. We analyze the tidal forces in the spacetime of an electrically charged Hayward regular black hole, obtaining the components of the tidal tensor and the geodesic deviation equation.

The first inspiral of two neutron stars observed in gravitational waves was remarkably close, allowing the kind of simultaneous gravitational wave and electromagnetic observation that had not been expected for several years. Their merger, followed by a gamma-ray burst and a kilonova, was observed across the spectral bands of electromagnetic telescopes. These GW and electromagnetic observations have

We review recent results on the existence of static black holes (BHs) without spatial isometries in four spacetime dimensions and propose a general framework for their study. These configurations are regular on and outside a horizon of spherical topology. Two different mechanisms allowing for their existence are identified. The first one relies on the presence of a solitonic limit of the BHs; when

Substellar objects of ultrashort periods (less than 50 min) orbiting central stars and many ultracompact star binary systems of even smaller periods (less than 10 min) have been optically detected in the last few years. Their gravitational luminosities can be of the same order or even much greater than their electromagnetic counterparts thereby also comprising a special class of targets for the Large

Perturbations in a draining vortex can be described analytically in terms of confluent Heun functions. In the context of analogue models of gravity in ideal fluids, we investigate analytically the absorption length of waves in a draining bathtub, a rotating black hole analogue, using confluent Heun functions. We compare our analytical results with the corresponding numerical ones, obtaining excellent

A Buchdahl star is a highly compact star for which the boundary radius R obeys R=98r+, where r+ is the gravitational radius of the star itself. A quasiblack hole is a maximum compact star, or more generically a maximum compact object, for which the boundary radius R obeys R=r+. Quasiblack holes are objects on the verge of becoming black holes. Continued gravitational collapse ends in black holes and

We study the impact of assumptions made about the neutrino mass ordering on cosmological parameter estimation with the purpose of understanding whether in the future it will be possible to infer the specific neutrino mass distribution from cosmological data. We find that although the commonly used assumption of a degenerate neutrino hierarchy is manifestly wrong and leads to changes in cosmological

Einstein’s General Relativity (GR) is possibly one of the greatest intellectual achievements ever conceived by the human mind. In fact, over the last century, GR has proven to be an extremely successful theory, with a well established experimental footing, at least for weak gravitational fields. Its predictions range from the existence of black holes and gravitational radiation (now confirmed) to the

In this paper, I show that there exists a new way to obtain scalar–tensor field theories by combining a special scalar field on the cotangent bundle with a scalar field on spacetime. These two scalar fields act as a generating function for the metric tensor. When using these two scalar fields in the Horndeski Lagrangians, we discover, while seeking Friedmann–Lemaître–Robertson–Walker-type cosmological

Horizons of black holes or cosmologies are peculiar loci of spacetime, where interesting physical effects take place, some of which are probed by recent (EHT and LIGO) and future experiments (ET and LISA). We discuss that there are boundary degrees of freedom residing at the horizon. We describe their symmetries and their interactions with gravitational waves. This fits into a larger picture of boundary

We explain how Hawking radiation stores significant amount of information in high-order correlations of quantum fields. This information can be retrieved by multi-time measurements on the quantum fields close to the black hole horizon. This result requires no assumptions about quantum gravity, it takes into account the differences between Gibbs’s and Boltzmann’s accounts of thermodynamics, and it clarifies

The epitome of a causal or anti-chronological behavior would be to see a clock running backwards in time. In this essay, we point out that this is indeed possible, but there is no problem with causality. What you see is not what is really happening. Locally, causality is always respected. However, our observation should be cause for pause to astronomers and cosmologists, who strictly observe events

In this paper, we have derived the field equations in an extended theory of gravity in an anisotropic spacetime background and in the presence of magnetic field. The physical and geometrical parameters of the models are determined with respect to the Hubble parameter using some algebraic approaches. A time varying scale factor has been introduced to analyze the behavior of the model. From some diagnostic

The scalar–spinor interaction Lagrangian is presented by the Yukawa potential. In dS ambient space formalism, the interaction Lagrangian of scalar–spinor fields was obtained from a new transformation which is very similar to the gauge theory. The interaction of massless minimally coupled (mmc) scalar and spinor fields was investigated. The Minkowski limit of the mmc scalar field and massive spinor

Gravity duals for a class of UV complete minimally supersymmetric nonconformal gauge theories require deformed conifolds with fluxes. However these manifolds do not allow for the standard Kähler or conformally Kähler metrics on them, instead the metrics are fully non-Kähler. We take a generic such configuration of a non-Kähler deformed conifold with fluxes and ask what constraints do supersymmetry

In this paper, we study the quantization of Dirac field theory in the κ-deformed space–time. We adopt a quantization method that uses only equations of motion for quantizing the field. Starting from κ-deformed Dirac equation, valid up to first order in the deformation parameter a, we derive deformed unequal time anticommutation relation between deformed field and its adjoint, leading to undeformed

Exploring the concept of the extended Galilei group G. Representations for field theories in a symplectic manifold have been derived in association with the method of the Wigner function. The representation is written in the light-cone of a de Sitter space–time in five dimensions. A Hilbert space is constructed, endowed with a symplectic structure, which is used as a representation space for the Lie

The concept of traversable wormhole, a hypothetical tunnel-like structure is initially proposed by Morris and Thorne (Am. J. Phys.56, 395 (1988)) by using Einstein’s general relativity theory. Harko et al. (Phys. Rev. D84, 024020 (2011)) defined F(R,T) gravity as an extended gravitational theory having terms R and T as Ricci scalar and trace of energy momentum respectively. In this article, we explore

The relativistic quantum mechanics of the electron in an inhomogeneous magnetic field problem is solved exactly in terms of the momentum space path integral formalism. We adopt the space–time transformation methods, which are α-point discretization dependent, to evaluate quantum corrections. The propagator is calculated, the energy eigenvalues and their associated curves are illustrated. The limit

We study the τ+τ− decay mode of a light CP-odd Higgs boson of the NMSSM, a1, produced in bottom-gluon fusion at the LHC. It is shown that for high luminosity of the LHC, there exist regions of the NMSSM parameter space that can be exploited to detect the a1 through this channel.

We consider the growth of the action for black hole space–time with a fundamental string. Our interest is to find the difference of the behavior between black holes with three different topologies in the scenario of complexity-action conjecture. These black holes have positive, negative and zero curvatures. We would like to calculate the action growth of these systems with a probe fundamental string

The electromagnetic field ground state, a zero-energy cosmic field permeating all of space, issues naturally from Maxwell’s electromagnetic theory and its fluctuations may generate transient photons conferring a physical solution to the vacuum energy scale problem. They are more significant at long wavelengths underlying principally the low frequency up to infrared cosmic radiation background. Assuming

Recently it has been speculated that a set of infinitesimal VirasoroL⊗VirasoroR diffeomorphisms exist which act nontrivially on the horizon of some black holes such as Kerr and Kerr–Newman black holes.1,2 Having applied this symmetry in covariant phase space formalism, one can obtain Virasoro charges as surface integrals on the horizon. Kerr–Bolt space–time is well known for its asymptotically topology

We analyze the results obtained from a model consisting of the interaction between the electric quadrupole moment of a moving particle and an electric field. We argue that the system does not support bound states because the motion along the z axis is unbounded. It is shown that the author obtains a wrong bound-state spectrum for the motion in the x−y plane and that the existence of allowed cyclotron

Petrogenetic relationships among members of the brachinite family were established by analyzing major and trace element concentrations of minerals for 9 representative specimens: Al Huwaysah 010, Eagles Nest, Northwest Africa (NWA) 4882, NWA 5363, NWA 7297, NWA 7299, NWA 11756, Ramlat as Sahmah (RaS) 309, and Reid 013. The brachinite family, which includes brachinites and ungrouped achondrites with

In this article, we study the Zc(3900) with the QCD sum rules in details by including the two-particle scattering state contributions and nonlocal effects between the diquark and antidiquark constituents. The two-particle scattering state contributions cannot saturate the QCD sum rules at the hadron side, the contribution of the Zc(3900) plays an unsubstitutable role, we can saturate the QCD sum rules

In our recent publications, the partition function of the Gross–Witten–Wadia unitary matrix model with the logarithmic term has been identified with the τ function of a certain Painlevé system, and the double scaling limit of the associated discrete Painlevé equation to the critical point provides us with the Painlevé II equation. This limit captures the critical behavior of the su(2), Nf=2, 𝒩=2 supersymmetric