Matter Sector Research Articles

Reheating process in the R 2 inflationary model with the baryogenesis scenario

Post-inflationary evolution and (re)heating of the viable inflationary model, the R 2 one, is made more realistic by including the leptogenesis scenario into it. For this purpose, right-handed Majorana neutrinos with a large mass are added to the matter sector of the Standard Model to explain the neutrino oscillation experiments and the baryon asymmetry of the Universe. We have found parameters that characterize this model: non-minimal coupling of the Higgs field ξ, the mass of the right-handed Majorana neutrino MN α and the Yukawa coupling matrix components for the right-handed Majorana neutrino. We have analyzed the effect of these parameters on the reheating process and leptogenesis in this model and how they affect the resultant physical quantities: spectral parameters of primordial perturbations and baryon asymmetry.

Impact of charge on complexity analysis and isotropic decoupled solutions in gravity

In this paper, we formulate two exact charged solutions to the field equations by extending the domain of existing anisotropic models with the help of minimal gravitational decoupling in theory. For this, the anisotropic fluid distribution is considered as a seed source that is extended through the inclusion of a new gravitational source. The influence of the later matter configuration is controlled by the decoupling parameter. We formulate the field equations corresponding to the total matter source that are then decoupled into two distinct sets by implementing a transformation only on the radial metric coefficient. Both of these under-determined sets correspond to their parent sources. Some well-behaved forms of the metric potentials are taken into account to deal with the first set of equations. On the other hand, we solve the second set corresponding to an additional source by taking different constraints on the matter sector. We then consider the radius and mass of a compact star 4U 1820 − 30 to analyze the physical feasibility of the resulting solutions for a particular modified model. It is concluded that our resulting solutions show stable behavior for certain values of the decoupling parameter and charge.

Beyond islands: a free probabilistic approach

We give a free probabilistic proposal to compute the fine-grained radiation entropy for an arbitrary bulk radiation state, in the context of the Penington-Shenker-Stanford-Yang (PSSY) model where the gravitational path integral can be implemented with full control. We observe that the replica trick gravitational path integral is combinatorially matching the free multiplicative convolution between the spectra of the gravitational sector and the matter sector respectively. The convolution formula computes the radiation entropy accurately even in cases when the island formula fails to apply. It also helps to justify this gravitational replica trick as a soluble Hausdorff moment problem. We then work out how the free convolution formula can be evaluated using free harmonic analysis, which also gives a new free probabilistic treatment of resolving the separable sample covariance matrix spectrum.The free convolution formula suggests that the quantum information encoded in competing quantum extremal surfaces can be modelled as free random variables in a finite von Neumann algebra. Using the close tie between free probability and random matrix theory, we show that the PSSY model can be described as a random matrix model that is essentially a generalization of Page’s model. It is then manifest that the island formula is only applicable when the convolution factorizes in regimes characterized by the one-shot entropies. We further show that the convolution formula can be reorganized to a generalized entropy formula in terms of the relative entropy.

A fractional matter sector for general relativity

In this work, we construct a fractional matter sector for general relativity. In particular, we propose a suitable fractional anisotropy function relating both the tangential and radial pressure of a spherically symmetric fluid based on the Grünwald–Letnikov fractional derivative. The system is closed by implementing the polytropic equation of state for the radial pressure. We solve the system of integro-differential equations by Euler’s method and explore the behavior of the physical quantities, namely, the normalized density energy, the normalized mass function, and the compactness.

Explaining interactions in collaborative innovation arrangements: How organizations influence their representatives’ interactions in collaborative innovation arrangements

Innovation through collaboration has been increasingly adopted to tackle complex social issues. As a result, the development of public sector innovations is to a lesser degree an ‘in-house’ matter and public sector innovations are increasingly more developed in collaborative arrangements that force organizations to interact across organizational borders. Despite the growing body of literature on collaborative innovation, little is known about the influence of organizations on the interactions of their members when they are acting on behalf of their organization in such collaborative arrangements. Through social network analysis, we examine how organizations influence the eagerness of their representatives in arrangements for collaborative innovation to engage in interactions outside official meetings with other participants. We found that the representative’s freedom to act and the extent to which the higher-level managers of the own organization sees the innovation project as a priority stimulates the extent to which the representative interacts with other participants in the arrangement. Moreover, reciprocity and having a coordinating role in the process determines interaction as well.

A tilt instability in the cosmological principle

We show that the Friedmann–Lemaître–Robertson–Walker (FLRW) framework has an instability towards the growth of fluid flow anisotropies, even if the Universe is accelerating. This flow (tilt) instability in the matter sector is invisible to Cosmic No-Hair Theorem-like arguments, which typically only flag shear anisotropies in the metric. We illustrate our claims in the setting of “dipole cosmology”, the maximally Copernican generalization of FLRW that can accommodate a flow. Simple models are sufficient to show that the cosmic flow need not track the shear, even in the presence of a positive cosmological constant. We also emphasize that the growth of the tilt hair is fairly generic if the effective equation of state w rightarrow -1 at late times (as it does in standard cosmology), irrespective of the precise model of dark energy. The generality of our theoretical result puts various recent observational claims about late time anisotropies and cosmic dipoles in a new light.

Custodial and SUSY 2HDM breaking under interfering condensates’ Goldstone bosons

The Higgs condensates are proven along with the minimal versions of the hyper-symmetric 2HDM extensions when containing Supersymmetry that can play the role of oscillators for the CPC and CPV interferences, up to via [Formula: see text]. With the uncharged Higgs inclusion (considering the uncharged Goldstone Bosons compared to the spontaneously broken SM-like Higgs), the symmetric [Formula: see text] and anti-symmetric [Formula: see text] linear combinations of an ‘[Formula: see text]’ and a rescaled [Formula: see text], where masses of [Formula: see text]GeV and [Formula: see text][Formula: see text]GeV, such as under the condensate’s boundary impacts. The range of the [Formula: see text]s would be up to where the composed singlet and triplet can interchange, then, they approach the Custodial SUSY at a Triple point transition with a Goldstone-type order mass [Formula: see text][Formula: see text]GeV, as well into their Dark Matter sectors’ cut-off [Formula: see text], (including [Formula: see text]) up to order 1.7[Formula: see text]TeV. That will lead to opening the way to measure the existence of Supersymmetry, indirectly at the least, through any dominance of [Formula: see text]-violating Higgs decays.

Shift symmetries and duality web in gauge theories

Using a generalised Noether prescription we are able to extract all the currents and their conservation laws in space dependent shift symmetric theories. Various identities among the currents in the matter sector are found that form the basis for revealing a dual picture when the full interacting theory is considered by coupling to gauge fields. The coupling is achieved in terms of vector fields by adhering to a modified minimal prescription which is also supported by an iterative Noether scheme. Further, this scheme shows that couplings can also be introduced using higher rank tensor gauge fields that have appeared in recent discussions on fractons. We reveal a connection among these descriptions (using vector or tensor fields) through certain duality maps that relate the various fields (gauge, electric and magnetic) in the two cases. A correspondence is established among the Gauss' law, Faraday's law and Ampere's law. Explicit calculations are provided for linear and quadratic shift symmetric lagrangians.

Chiral Instabilities and the Fate of Chirality Imbalance in Non-Abelian Plasmas.

We present a microscopic study of chiral plasma instabilities and axial charge transfer in non-Abelian plasmas with a strong gauge-matter coupling g^{2}N_{f}=64, by performing 3+1D real-time classical-statistical lattice simulation with dynamical fermions. We explicitly demonstrate for the first time that-unlike in an Abelian plasma-the transfer of chirality from the matter sector to the gauge fields occurs predominantly due to topological sphaleron transitions. We elaborate on the similiarities and differences of the axial charge dynamics in cold Abelian U(1) and non-Abelian SU(2) plasmas, and comment on the implications of our findings for the study of anomalous transport phenomena, such as the chiral magnetic effect in QCD matter.

A hidden self-interacting dark matter sector with first-order cosmological phase transition and gravitational wave

A hidden self-interacting dark matter sector with first-order cosmological phase transition and gravitational wave

Cylindrical wormholes and electromagnetic field

In this manuscript, we study the construction of static cylindrically symmetric thin shell wormhole models with an electric charge in the background of f(R,T) gravity. We utilized “cut and paste” technique to match two identical spacetimes across the separation hypersurface Σ. In this gravity, f is a generic function of the Ricci scalar (R) and the trace of the stress-energy tensor (T), as the gravitational sources. We continue our systematic investigation by using specific f(R,T) model with quadratic corrections in R. In this scenario, we assume that the isotropic perfect fluid adequately represents the matter sector, implying that matter at the shell is sustained by generalized Chaplygin gas. Using generalized Chaplygin gas, to ensure a consistent matching of the two spacetimes across the separation hypersurface Σ, suitable boundary conditions and constraints are imposed. These conditions guarantee the continuity of the metric coefficients, the electric charge distribution, and other relevant quantities at the thin shell within the framework of the quadratic f(R,T) gravity. The effects of mass, equation of state parameters, and electric charge are examined on the stability of static wormhole models for the widest possible range of model parameters. The positive value of the second derivative of potential at throat radius is used to characterize the stability requirement which is indicated via plots. We study the presence of charge which might affect the stability region of constructed wormhole. It is suggested that a charged wormhole model might be more stable than an uncharged one.

Boosting indirect detection of a secluded dark matter sector

Boosting indirect detection of a secluded dark matter sector

Multi-scalar theories of gravity with direct matter couplings and their parametrized post-Newtonian parameters

We study theories of gravity including, in addition to the metric, several scalar fields in the gravitational sector. The particularity of this work is that we allow for direct couplings between these gravitating scalars and the matter sector, which can generally be different for the source and the probe of gravity, in addition to the universal interactions generated by the Jordan frame metric. The weak gravity regime of this theory, which would describe solar-system experiments, is studied using the parametrized post-Newtonian (PPN) formalism. We derive the expression of the ten parameters of this formalism. Among them, ζ 3 and ζ 4 are modified with respect to their values in the theories without direct couplings. This fact holds even after eliminating the direct couplings between the gravitating scalars and the energy density of the source, by redefinition of the Jordan frame. All other PPN parameters are insensitive to the direct couplings once in the correctly identified Jordan frame. When direct couplings are different for the source and the probe of gravity, they make non-relativistic probes deviate from the geodesics of the PPN metric in this frame, already at Newtonian order. Such couplings would thus be directlydetectable and would have been excluded by experiments.This shows that, contrary to the claims in the recent literature, it is impossible to screen the presence of gravitating scalars relying only on a curved target space and direct couplings to matter.

An anisotropic stellar fluid configuration with vanishing complexity

In this work, we construct a new stellar model in the regime of anisotropic fluid pressure using the concept of vanishing complexity for spherically symmetric fluid distributions (Herrera in Phys Rev D 97:044010, 2018) and a convenient ansatz in order to close the Einstein’s field equations. The resulting model fulfills the fundamental physical acceptability stellar conditions for a specific set of compactness factor. The stability and its response against fluctuations in the matter sector is also investigated.

Quantum avoidance of Gödel’s closed timelike curves

In a large class of nonlocal as well as local higher derivative theories minimally coupled to the matter sector, we investigate the exactness of two different classes of homogeneous Gödel-type solutions, which may or may not allow closed time-like curves (CTC). Our analysis is limited to spacetimes solving the Einstein’s EoM, thus we can not exclude the presence of other Gödel-type solutions solving the EoM of local and nonlocal higher derivative theories but not the Einstein’s EoM. It turns out that the homogeneous Gödel spacetimes without CTC are basically exact solutions for all theories, while the metrics with CTC are not exact solutions of (super-)renormalizable local or nonlocal gravitational theories. Hence, the quantum renormalizability property excludes theories suffering of the Gödel’s causality violation. We also comment about nonlocal gravity non-minimally coupled to matter. In this class of theories, all the Gödel’s spacetimes, with or without CTC, are exact solutions at classical level. However, the quantum corrections, although perturbative, very likely spoil the exactness of such solutions. Therefore, we can state that the Gödel’s Universes with CTC and the super-renormalizability are mutually exclusive.

Irreversible Geometrothermodynamics of Open Systems in Modified Gravity.

In this work, we explore the formalism of the irreversible thermodynamics of open systems and the possibility of gravitationally generated particle production in modified gravity. More specifically, we consider the scalar-tensor representation of f(R,T) gravity, in which the matter energy-momentum tensor is not conserved due to a nonminimal curvature-matter coupling. In the context of the irreversible thermodynamics of open systems, this non-conservation of the energy-momentum tensor can be interpreted as an irreversible flow of energy from the gravitational sector to the matter sector, which, in general, could result in particle creation. We obtain and discuss the expressions for the particle creation rate, the creation pressure, and the entropy and temperature evolutions. Applied together with the modified field equations of scalar-tensor f(R,T) gravity, the thermodynamics of open systems lead to a generalization of the ΛCDM cosmological paradigm, in which the particle creation rate and pressure are considered effectively as components of the cosmological fluid energy-momentum tensor. Thus, generally, modified theories of gravity in which these two quantities do not vanish provide a macroscopic phenomenological description of particle production in the cosmological fluid filling the Universe and also lead to the possibility of cosmological models that start from empty conditions and gradually build up matter and entropy.

Energy momentum tensor of a non-minimally coupled scalar from the equivalence of the Einstein and Jordan frames

Unlike the minimally coupled gravity theory where matter is coupled with gravity in such a manner so that one can differentiate the matter and gravity sector uniquely, the non-minimally coupled theories (NMCT) are distinguished by the intermingling of two. As a consequence of this the calculation of the energy momentum tensor (EMT) in NMCT is beset with an arbitrariness. In this paper we provide an algorithm based on the well known equivalence between Jordan frame and Einstein frame formulations which enables us to construct the EMT for NMCT in a unique way.

Effective dark energy through spin-gravity coupling

We investigate cosmological scenarios with spin-gravity coupling. In particular, due to the spin of the baryonic and dark matter particles and its coupling to gravity, they probe an effective spin-dependent metric, which can be calculated semi-classically in the Mathisson-Papapetrou-Tulczyjew-Dixon formalism. Hence, the usual field equations give rise to modified Friedmann equations, in which the extra terms can be identified as an effective dark-energy sector. Additionally, we obtain an effective interaction between the matter and dark-energy sectors. In the case where the spin-gravity coupling switches off, we recover standard ΛCDM cosmology. We perform a dynamical system analysis and we find a matter-dominated point that can describe the matter era, and a stable late-time solution corresponding to acceleration and dark-energy domination. For small values of the spin coupling parameter, deviations from ΛCDM concordance scenario are small, however for larger values they can be brought to the desired amount, leading to different dark-energy equation-of-state parameter behavior, as well as to different transition redshift from acceleration to deceleration. Finally, we confront the model predictions with Hubble function data.

Scalaron Decay in Perturbative Quantum Gravity

A certain quadratic gravity model provides a successfully inflationary scenario. The inflation is driven by the new scalar degree of freedom called scalaron. After the end of inflation the scalaron decays in matter and dark matter degrees of freedom reheating the Universe. We study new channels by which the scalaron can transfer energy to the matter sector. These channels are annihilation and decay via intermediate graviton states. Results are obtained within perturbative quantum gravity. In the heavy scalaron limit only scalar particles are produced by the annihilation channel. Scalaron decays in all types of particles are allowed. In the light scalaron limit decay channel is strongly suppressed. Boson production via the annihilation channel is expected to be dominant at the early stages of reheating, while fermion production will dominate later stages.

Modified gravity and cosmology with nonminimal direct or derivative coupling between matter and the Einstein tensor

We construct new classes of modified theories in which the matter sector couples with the Einstein tensor, namely we consider direct couplings of the latter to the energy-momentum tensor, and to the derivatives of its trace. We extract the general field equations, which do not contain higher-order derivatives, and we apply them in a cosmological framework, obtaining the Friedmann equations, whose extra terms give rise to an effective dark energy sector. At the background level we show that we can successfully describe the usual thermal history of the universe, with the sequence of matter and dark-energy epochs, while the dark-energy equation-of-state parameter can lie in the phantom regime, tending progressively to $-1$ at present and future times. Furthermore, we confront the theory with Cosmic Chronometer data, showing that the agreement is very good. Finally, we perform a detailed investigation of scalar and tensor perturbations, and extracting an approximate evolution equation for the matter overdensity we show that the predicted behavior is in agreement with observations.