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The "new standard cosmology", based on the theory of inflation, has very impressive observational support. I review some outstanding problems of the new cosmology and the global view of the universe -- the multiverse -- that it suggests. I focus in particular on prospects for further observational tests of inflation and of the multiverse., Invited talk at TAUP conference, Rome, July 2009

In this work we analyze how the spectrum of primordial scalar perturbations is modified, within the emergent universe scenario, when a particular version of the Continuous Spontaneous Localization (CSL) model is incorporated as the generating mechanism of initial perturbations, providing also an explanation to the quantum-to-classical transition of such perturbations. On the other hand, a phase of super-inflation, prior to slow-roll inflation, is a characteristic feature of the emergent universe hypothesis. In recent works, it was shown that the super-inflation phase could generically induce a suppression of the temperature anisotropies of the CMB at large angular scales. We study here under what conditions the CSL maintains or modifies these characteristics of the emergent universe and their compatibility with the CMB observations., Comment: 15 pages, 5 figures. Some references added. Version accepted in EPJC

We propose a minimal model that can explain the electroweak scale, neutrino masses, Dark Matter (DM), and successful inflation all at once based on the multicritical-point principle (MPP). The model has two singlet scalar fields that realize an analogue of the Coleman-Weinberg mechanism, in addition to the Standard Model with heavy Majorana right-handed neutrinos. By assuming a $Z_2 $ symmetry, one of the scalars becomes a DM candidate whose property is almost the same as the minimal Higgs-portal scalar DM. In this model, the MPP can naturally realize a saddle point in the Higgs potential at high energy scales. By the renormalization-group analysis, we study the critical Higgs inflation with non-minimal coupling $\xi |H|^2 R$ that utilizes the saddle point of the Higgs potential. We find that it is possible to realize successful inflation even for $\xi=25$ and that the heaviest right-handed neutrino is predicted to have a mass around $10^{14}$ GeV to meet the current cosmological observations. Such a small value of $\xi$ can be realized by the Higgs-portal coupling $\lambda_{SH}\simeq 0.32$ and the vacuum expectation value of the additional neutral scalar $\langle\phi\rangle\simeq 2.7$ TeV, which correspond to the dark matter mass 2.0 TeV, its spin-independent cross section $1.8\times10^{-9}$ pb, and the mass of additional neutral scalar 190 GeV., Comment: 30 pages, 7 figures; Version accepted in EPJC (v2)

Analytic and numerical techniques are presented for computing gravitational production of scalar particles in the limit that the inflaton mass is much larger than the Hubble expansion rate at the end of inflation. These techniques rely upon adiabatic invariants and time modeling of a typical inflaton field which has slow and fast time variation components. A faster computation time for numerical integration is achieved via subtraction of slowly varying components that are ultimately exponentially suppressed. The fast oscillatory remnant results in production of scalar particles with a mass larger than the inflationary Hubble expansion rate through a mechanism analogous to perturbative particle scattering. An improved effective Boltzmann collision equation description of this particle production mechanism is developed. This model allows computation of the spectrum using only adiabatic invariants, avoiding the need to explicitly solve the inflaton equations of motion., 37 pages, 5 figures

Constant-rate inflation, including ultra-slow-roll as a special case, has been widely applied to the formation of primordial black holes with significant deviation from the standard slow-roll conditions at both the growing and decaying phases of the power spectrum. We derive analytic solutions for the curvature perturbations with respect to the late-time scaling dimensions (conformal weights) constrained by the dilatation symmetry of the de Sitter background and show that the continuity of conformal weights across different rolling phases is protected by the adiabatic condition of the inflaton perturbation. The temporal excitation of subleading states (with the next-to-lowest conformal weights), recorded as the "steepest growth" of the power spectrum, is triggered by the entropy production in the transition from slow-roll to constant-rate phases., Comment: 18 + 4 pages, 6 figures; v2: references added, provided entropy production as a criterion for the steepest growth; v3: minor corrections, version matched with publication

The policy debate in Turkey over the impact of interest rate on inflation concerns the question of what policymakers should do when faced with volatile and high inflation. Motivated by this discussion, we provide an empirical analysis by connecting the cost channel to the Phillips relation. Our findings prove the existence of the cost channel. However, other determinants of inflation —labor share of income, prices of imported inputs, and consumption goods —dominate the cost channel in Turkey.

The interactions between spin of fermionic matter and torsion in Einstein-Cartan-Sciama-Kibble (ECSK) theory of gravity provide a repulsive gravitational potential at very dense states of fermionic matter, which prevents the formation of black hole singularities inside the deeper horizon. While the fermionic matter in the black hole is attracted by the black hole at the beginning, after a critical point it is repelled to bounce at a critical high density and then expand into other side of the horizon as a newly created space, which may be considered as a non-singular, closed universe. We constructed the action of these fermions in a black hole with torsion in the framework of ECSK theory of gravity from which the free Dirac action is inferred and the interaction potential is obtained. Also, this scenario naturally solves the flatness and horizon problems of cosmology without introducing finely tuned scalar fields, or more complicated functions of the Ricci scalar R in gravitational action.

We describe a new phenomenon in quantum cosmology: self-organised localisation. When the fundamental parameters of a theory are functions of a scalar field subject to large fluctuations during inflation, quantum phase transitions can act as dynamical attractors. As a result, the theory parameters are probabilistically localised around the critical value and the Universe finds itself at the edge of a phase transition. We illustrate how self-organised localisation could account for the observed near-criticality of the Higgs self-coupling, the naturalness of the Higgs mass, or the smallness of the cosmological constant., 104 pages, 12 figures. v3: Measure problem discussion extended and references added. Version to be published in JHEP

Quasi-conformal models are an appealing scenario that can offer naturally a strongly supercooled phase transition and a period of thermal inflation in the early Universe. A crucial aspect for the viability of these models is how the Universe escapes from the supercooled state. One possibility is that thermal inflation phase ends by nucleation and percolation of true vacuum bubbles. This route is not, however, always efficient. In such case another escape mechanism, based on the growth of quantum fluctuations of the scalar field that eventually destabilize the false vacuum, becomes relevant. We study both of these cases in detail in a simple yet representative model. We determine the duration of the thermal inflation, the curvature power spectrum generated for the scales that exit horizon during the thermal inflation, and the stochastic gravitational wave background from the phase transition. We show that these gravitational waves provide an observable signal from the thermal inflation in almost the entire parameter space of interest. Furthermore, the shape of the gravitational wave spectrum can be used to ascertain how the Universe escaped from supercooling., Comment: 11 pages, 6 figures. published version

Some terms identify enigmata of today’s cosmology: “Inflation” is expected to explain the homogeneity and isotropy of the cosmic background. The repulsive force of a “dark energy” shall prevent a re-collapse of the cosmos. The additional gravitational effect of a “dark matter” was originally supposed to explain the deviations of the rotation curves of the galaxies from Kepler’s laws. Adopting a theory founded on the core notion of absolute quantum information–Protyposis–being a cosmological concept from the outset, the observed phenomena can be explained without postulating further unknown specific “particles” or “fields”. Moreover, this theory allows for a rationalization of the fact that huge black holes with their enormous jet structures, acting as “seeds” of the galaxies, are detected ever closer to the big bang. The problem of the rotation curves in the galaxies can be addressed outside of General Relativity within a Newtonian approximation: by an attenuation of the gravitational acceleration as in the modified Newtonian dynamics, or by the effect of additional invisible “particles of dark matter”, yet unknown and not yet established in natural sciences. Within the Protyposis theory, these problems are solved without having to invent a lot of parameters. The cosmology of the Protyposis causes the change of the gravitational acceleration in the vicinity of large (black hole) masses and, at the same time, avoids a recollapse of the cosmos for which a cosmological constant or “dark energy” was invented.

We investigate the effects of logarithmic corrections to the minimal Kahler potential in supergravity. They provide a constant Fayet–Iliopoulos term, but can induce singularities in the “F-term” scalar potential. If a proper superpotential is supplemented, such singularities can be avoided at the minimum of the scalar potential and the relevant U(1) gauge symmetry as well as supersymmetry can be broken. We apply this mechanism to a D-term hybrid inflationary model such that the U(1) gauge symmetry is broken during the inflation era and the resultant cosmic strings are diluted away. We employ a non-minimal form of the gauge kinetic function that includes an inflaton’s contribution such that the spectral index in the minimal D-term inflationary model is cured to the observed value. The tensor-to-scalar ratio is extremely small.

A self-consistent explanation of the approximately flat three-dimensional space is one of the major conceptual issues of any cosmological model, determining its viability and competitiveness among the various theoretical proposals. In particular, just the inability to resolve the problem of flatness was one of the reasons to reject the old “pre-inflationary” cosmological model and to change it by the inflationary scenario. Here, we briefly recall how the three-dimensional flatness can or cannot be explained in the various models of the early Universe and discuss in detail the case of uncertainty-mediated inflation, which was suggested in our previous paper [7]. As follows from our analysis, the approximately flat 3D space in the last-mentioned model can really be formed “dynamically,” starting from generic initial conditions. Taking into account that this model also well resolves the causality problems in the early Universe [8], the uncertainty-mediated inflation might be a reasonable alternative to other inflationary scenarios.

In this paper we first investigate the local well-posedness and global existence with large damping coefficient for the Cauchy problem of a Camassa-Holm type equation with cubic and quartic nonlinearities in nonhomogeneous Besov spaces. Then we obtain a blow-up criteria and present norm inflation which implies ill-posedness for the equation in critical Besov spaces.

In previous works we have derived a Running Vacuum Model (RVM) for a string Universe, which provides an effective description of the evolution of 4-dimensional string-inspired cosmologies from inflation till the present epoch. In the context of this "stringy RVM" version, it is assumed that the early Universe is characterised by purely gravitational degrees of freedom, from the massless gravitational string multiplet, including the antisymmetric tensor field. The latter plays an important role, since its dual gives rise to a `stiff' gravitational-axion "matter", which in turn couples to the gravitational anomaly terms, assumed to be non-trivial at early epochs. In the presence of primordial gravitational wave (GW) perturbations, such anomalous couplings lead to an RVM-like dynamical inflation, without external inflatons. We review here this framework and discuss potential scenarios for the generation of such primordial GW, among which the formation of unstable domain walls, which eventually collapse in a non-spherical-symmetric manner, giving rise to GW. We also remark that the same type of "stiff" axionic matter could provide, upon the generation of appropriate potentials during the post-inflationary eras, (part of) the Dark Matter (DM) in the Universe, which could well be ultralight, depending on the parameters of the string-inspired model. All in all, the new (stringy) mechanism for RVM-inflation preserves the basic structure of the original (and more phenomenological) RVM, as well as its main advantages: namely, a mechanism for graceful exit and for generating a huge amount of entropy capable of explaining the horizon problem. It also predicts axionic DM and the existence of mild dynamical Dark Energy (DE) of quintessence type in the present universe, both being "living fossils" of the inflationary stages of the cosmic evolution., Comment: 75 pages revtex, 6 pdf figures incorporated

We carry out a systematic study of the response of companion stars in massive binaries after being impacted by supernova ejecta. A total of 720 1D stellar evolution calculations are performed to follow the inflation and contraction of the star in response to the energy injection and how it depends on various parameters. We find that the maximum luminosity achieved during the inflated phase is only dependent on the stellar mass and we derive an analytic formula to describe the relation. There is also a tight correlation between the duration of expansion and the intersected energy. These correlations will be useful to constrain pre-supernova binary parameters from future detections of inflated companions. We also discuss the possible outcomes of the binary system when the companion inflation is taken into account. Based on simple binary population synthesis, we estimate that $\sim$1-3% of stripped-envelope supernovae may have observable inflated companions. Finally, we apply our models to the observed companion of SN2006jc and place strong constraints on the possible pre-supernova binary parameters., 15 pages, 15 figures, Accepted for publication in MNRAS

Solid inflation is a cosmological model where inflation is driven by fields which enter the Lagrangian in the same way as body coordinates of a solid matter enter the equation of state, spontaneously breaking spatial translational and rotational symmetry. We construct a simple generalization of this model by adding a scalar field with standard kinetic term to the action. In our model the scalar power spectrum and the tensor-to-scalar ratio do not differ from the ones predicted by the solid inflation qualitatively, if the scalar field does not dominate the solid matter. The same applies also for the size of the scalar bispectrum measured by the non-linearity parameter, although our model allows it to have different shapes. The tensor bispectra predicted by the two models do not differ from each other in the leading order of the slow-roll approximation. In the case when contribution of the solid matter to the stress-energy tensor is much smaller than the contribution from the scalar field, the tensor-to-scalar ratio and the non-linearity parameter are amplified by factors $\epsilon^{-1}$ and $\epsilon^{-2}$ respectively., Comment: 23 pages, 3 figures

Objective: To present a new solution to the field equations obtained for higher dimensional LRS Bianchi type-I universe generated by means of a cloud of strings with particles connected to them with bulk viscosity in general relativity. Methods: To obtain the solutions of field equations of higher dimensional LRS Bianchi type-I universe we consider that the shear scalar of the model is proportional to the scalar expansion of the model (saq ), which leads to, c=b^n. The physical and geometrical behaviors of the model universe are studied by comparing with the present cosmological scenario and observations. Findings: It is observed that our model is anisotropic, expanding and decelerates at early stage and then accelerates in late universe giving the inflation model universe. Novelty: We obtained new solution to the field equations for higher dimensional LRS Bianchi type-I generated by means of a cloud of strings with bulk viscous fluid in general relativity. Keywords: LRS Bianchi TypeI Metric; Bulk Viscous Fluid; Strings

Maxwell equations and the equations of General Relativity are scale invariant in empty space. The presence of charge or currents in electromagnetism or the presence of matter in cosmology are preventing scale invariance. The question arises on how much matter within the horizon is necessary to kill scale invariance. The scale invariant field equation, first written by Dirac in 1973 and then revisited by Canuto et al. in 1977, provides the starting point to address this question. The resulting cosmological models show that, as soon as matter is present, the effects of scale invariance rapidly decline from \rho=0 to \rho_c and are forbidden for densities above \rho_c. The absence of scale invariance in this case is consistent with considerations about causal connection. Below \rho_c, scale invariance appears as an open possibility, which also depends on the occurrence of inflation in the scale invariant context. In the present approach, we identify the scalar field of the empty space in the Scale Invariant Vacuum (SIV) context to the scalar field \phi in the energy density expression of the vacuum at inflation. This leads to some constraints on the potential. This identification also solves the so-called ``cosmological constant problem''. In the framework of scale invariance,an inflation with a large number of e-foldings is also predicted. We conclude that scale invariance for models with densities below \rho_c is an open possibility; the final answer may come from high redshift observations, where differences from the LCDM models appear., Comment: 12 pages, 1 figure

A viable model for inflation driven by a torsion function in a Friedmann background is presented. The scalar spectral index in the interval $0.92\lesssim n_{s}\lesssim 0.97$ is obtained in order to satisfy the initial conditions for inflation. The post inflationary phase is also studied, and the analytical solutions obtained for scale factor and energy density generalizes that ones for a matter dominated universe, indicating just a small deviation from the standard model evolution. The same kind of torsion function used also describes satisfactorily the recent acceleration of the universe, which could indicate a possible unification of different phases, apart form specific constants., Comment: 8 pages, 2 figures, submitted to EPJC

We report the discovery of four new hot Jupiters with the Next Generation Transit Survey (NGTS). NGTS-15b, NGTS-16b, NGTS-17b, and NGTS-18b are short-period ($P, Accepted for publication in MNRAS

In this paper, we study the $$\alpha $$ -attractors in the framework of the Randall–Sundrum type II braneworld model. We consider the simplest E-model of $$\alpha $$ -attractors and apply the slow-roll approximation in high energy limit. In this scenario, we numerically investigate the inflationary parameters and show that high-energy brane corrections have significant effect on the parameter $$\alpha $$ ; namely, lower values of $$\alpha $$ are observationally preferred in this limit. The latter substantially reduces the tensor-to-scalar ratio of perturbations making the braneworld inflation compatible with observational data.

Starting with the de Broglie-Proca Lagrangian for a massive vector field, we calculate the number density of particles resulting from gravitational particle production (GPP) during inflation, with detailed consideration to the evolution of the number density through the reheating. We find plausible scenarios for the production of dark-photon dark matter of mass in a wide range, as low as a micro-electron volt to 1014 GeV. Gravitational particle production does not depend on any coupling of the dark photon to standard-model particles.

We study the effects of particle production on the evolution of the inflaton field in an axion monodromy model with the goal of discovering in which situations the resulting dynamics will be consistent with the swampland constraints. In the presence of a modulated potential the evolving background field (solution of the inflaton homogeneous in space) induces the production of long wavelength inflaton fluctuation modes. However, this either has a negligible effect on the inflaton dynamics (if the field spacing between local minima of the modulated potential is large), or else it traps the inflaton in a local minimum and leads to a graceful exit problem. On the other hand, the production of moduli fields at enhanced symmetry points can lead to a realization of trapped inflation consistent with the swampland constraints, as long as the coupling between the inflaton and the moduli fields is sufficiently large., The European Physical Journal C, 81 (2), ISSN:1434-6044, ISSN:1434-6052

Contracting cosmologies are known to be flawed with a shear instability, where the contribution from the anisotropic stress to the overall energy density grows as $a^{-6}$, with $a$ the scale factor. Classically, whether or not this contribution becomes important before the bounce depends on its initial value, which can always be sufficiently fine tuned to make it irrelevant. However, vacuum quantum fluctuations inevitably provide a non-vanishing source of anisotropic stress. In this work, we compute the minimum amount of shear that is obtained if one assumes that it vanishes initially, but lets quantum fluctuations build it up. In practice, we consider a massless test scalar field, and describe its quantum fluctuations by means of the stochastic "inflation" (though here applied to a contracting phase) formalism. We find that, if the equation-of-state parameter of the contraction satisfies $w>-1/9$, regardless of when the contracting phase is initiated, the time at which the shear becomes sizeable is always when the Hubble scale approaches the Planck mass (which is also where the bounce is expected to take place). However, if $w, Comment: matches the published version in EPJC

We would like to emphasize that, extraordinary physical concepts like Big bang, Inflation, Dark energy and Superluminal expansion demand super-normal efforts and need observational support. Observational data is raising day-by-day non-conformity and demanding changes in the original concepts. It is very interesting to note that James Peebles, the famous cosmologist and 2019 Nobel laureate strongly believes that Big bang concept is inappropriate in understanding the universe. It is better to understand and develop models of cosmology based on well supported physical concepts rather than extraordinary physical hypothesis. Unification point of view, quantum cosmology must be given a priority and one should make a note that, Spin is a basic property of quantum physics and rotation is a very common experience. In this context, with reference to life cycle of living creatures and independent of red-shift data, we have developed a quantum model of cosmology associated with Machian universe having Planck scale origin, total dark matter, light speed expansion, light speed rotation, equality of gravitational self energy density and thermal energy density, radially decreasing internal acceleration and radially increasing anisotropy. We are working on understanding and correlating observed redshift data in a unified approach. In this letter, we present various galactic applications of current cosmic angular velocity. Â

Objectives: To present a new solution to the field equations obtained for Bianchi type-III universe by using the law of variation of H, which yields constant DP. Methods: We study a Bianchi type-III cosmological model with a cloud strings with particles connected to them in Lyra geometry. To find the exact solutions of survival field equations we consider here that the shear scalar and scalar expansion are proportional to each other (saq ) that leads to the equation b = cm and secondly we adopt the assumption considering the Deceleration Parameter q as a negative constant quantity giving the inflationary model. The geometrical and physical properties are studied and compared with the recent observational data. Findings: The present model starts at t=0 with 0 volume and as time progresses it expands with accelerated rate and the model shows that the present universe is particle dominated. Keywords: Bianchi type III metric; inflation; Lyra geometry; cloud string; anisotropic

A concise summary of out-of-equilibrium dark matter production during post-inflationary reheating is presented. We show that the dark matter relic abundance is in general sensitive to the thermalization rate of the inflaton decay products, and the evolution of the temperature of the subsequently thermalized radiation. We discuss how smoking-gun signals, such as monochromatic neutrinos or gamma-ray lines, or Lyman-$\alpha$ data, can help constrain out-of-equilibrium DM models., Comment: 6 pages, 4 figures. Contribution to the IWARA 2020 conference proceedings

We reduplicate the Book “Dark Energy” by M. Li, X-D. Li, and Y. Wang, given zero-point energy calculation with an unexpected “length” added to the “width” of a graviton wave just prior to specifying the creation of “gravitons”, while using Karen Freeze’s criteria as to the breakup of primordial black holes to give radiation era contributions to GW generation. The GW generation will be when there is sufficient early universe density so as to break apart Relic Black holes of the order of Planck mass (1015 grams) which is about when the mass of relic black holes is created, 10-27 or so seconds after expansion starts. Needles to state a key result will be in the initial potential V calculated, in terms of other input variables.

A successful single parameter model has been formulated to match the observations of photons from type 1a supernovae which were previously used to corroborate the standard &#120556 cold dark matter model. The new single parameter model extrapolates all the way back to the cosmic background radiation (CMB) without requiring a separate model to describe inflation of the space dimensions after the Big Bang. This single parameter model assumes that spacetime forms a finite symmetrical manifold with positive curvature. For the spacetime manifold to be finite, the time dimension must also have positive curvature. This model was formulated to consider whether the curvature of the time dimension may be related to the curvature of the space dimensions. This possibility is not considered in the more complex models previously used to fit the available redshift data. The geometry for the finite spacetime manifold was selected to be compatible with the Friedmann equation with positive curvature. The manifold shape was motivated by an assumption that there exists a matter hemisphere (when considering time together with a single space dimension) and an antimatter hemisphere to give a symmetrical and spherical overall spacetime manifold. Hence, the space dimension expands from a pole to the equator, at a maximum value for the time dimension. This is analogous to the expansion of a circle of latitude on a globe from a pole to the equator. The three space dimensions are identical so that any arbitrary single space direction may be selected. The initial intention was to modify the assumed geometry for the spacetime manifold to account for the presence of matter. It was surprisingly found that, within the error of the reported measurements, no further modification was necessary to fit the data. The Friedmann equation reduces to the Schwarzschild equation at the equator so this can be used to predict the total amount of mass in the Universe. The resulting prediction is of the order of 1051 kg. The corresponding density of matter at the current time is approximately 1.6 × 10-28 kg·m-3.

We are using the book “Towards Quantum Gravity” with an article by Claus Kiefer as to a quantum gravity interpretation of the density matrix in the early universe. The density matrix we are using is a one loop approximation, with inflaton value and potential terms, like V (phi) using the Padmanabhan values one can expect if the scale factor is a ~a (Initial) times t ^ gamma. In doing so, we identify two time steps and presume a very small initial time step candidates initial time values which are from a polynomial for time values. A gravity wave analysis concludes our article with inflaton decay, which is finally linked to BHs. And then finally we show using work done by Hawking, et al. how this may give us Planck Sized Black Holes, in the onset of Inflation, with resulting consequences so outlined. A vastly simplified proof of BH masses of Planck mass is presented which ties in directly with issues of the mass of the inflaton initially generated by the 2nd derivative of the effective potential V (phi) at a time t ~4 times Planck time. And we include at the close questions as to DE, and data sets which may give credence to speculation as to different time flow rates at the start and then the conclusion later on, of expansion of our universe. The DE would be created by the breakup of the black holes due to a mechanism brought up by Dr. Freeze in 2012, and we also are using the future works section 8 to define the contours of our DE model which builds upon quite directly the sequence of material from pages 1 to 9 which are cited as to making connection between early universe conditions and the ideas of primordial DE models.

Inflation driven by a generic self-gravitating medium is an interesting alternative to study the impact of spontaneous spacetime symmetry breaking during a quasi de-Sitter phase, in particular the 4-dimensional diffeomorphism invariance of GR is spontaneously broken down to $ISO(3)$. The effective description is based on four scalar fields that describe the excitations of a supersolid. There are two phonon-like propagating scalar degrees of freedom that mix non-trivially both at early and late times and, after exiting the horizon, give rise to non-trivial correlations among the different scalar power spectra. The non-linear structure of the theory allows a secondary gravitational waves production during inflation, efficient enough to saturate the present experimental bound and with a blue-tilted spectral index., Comment: 32 pages, 8 figures. Few typos corrected and comments added

Researchers have long been aware of the existence of large HI structures and over the past decades, a large observational record of their properties has been assembled. Despite all the work that has been done, however, there is no consensus about their origin. In this paper, we will show that these structures can readily be understood within the framework of a new model of cosmology based on time-varying curvature and an unconventional model of nucleosynthesis. According to this model, all galaxies came into existence at the same time during nucleosynthesis as large proton gas clouds whose detailed structure was fixed by an imprint established in the vacuum during an initial Plank inflation. One of the predictions of the model is that all these proto-galaxy gas clouds reached the zero-velocity point of their expansion with sizes many times larger than their present-day size. The large outer HI rings are simply regions of this gas that remained at the maximum size as the core compacted to its present-day size. Similarly, the inner rings are regions that did compact with the galaxy core.

This paper introduces a cosmic expansion model with constant speed of cosmic spatial expansion via derivation and simulations, where the speed of cosmic spatial expansion equals the speed of light c. Simulation results show that the earliest observable universe time is t = 5.084 Gyrs where the current universe time T = 13.82 Gyrs, and the furthest observable distance at the earliest observable universe time t is S = 0.632R, where R is the cosmic radius at current universe time T. The above constant cosmic expansion model does not consider the inflation period in the early universe according to the Big Bang model, nor does it considered the cosmic acceleration in recent universe time. However, this simplified cosmic expansion model could be a benchmark that will be helpful to understand the cosmic expansion and the observable universe. Based on the derivation and simulation of the constant cosmic expansion model, the threshold of observable universe for the accelerated cosmic expansion model can also be calculated similarly, as far as the speed of cosmic spatial expansion at any universe time t can be provided.

The holographic principle is applied to a description of the Universe in the early stage of its evolution. As an example, we examine a cosmological model with a bounce with subsequent transition to the early stage of inflation. We investigate cosmological models based on a viscous liquid with a generalized equation of state in terms of the holographic cutoff proposed by Nojiri and Odintsov. Within the framework of these models, we have calculated the infrared radius in terms of the particle horizon or the event horizon. Energy conservation laws are obtained from the holographic point of view. The viscous liquid describing the bounce and the early Universe is presented as a generalization of holographic energy.

A cosmological model was developed using the equation of state of photon gas, as well as cosmic time. The primary objective of this model is to see if determining the observed rotation speed of galactic matter is possible, without using dark matter (halo) as a parameter. To do so, a numerical application of the evolution of variables in accordance with cosmic time and a new state equation was developed to determine precise, realistic values for a number of cosmological parameters, such as the energy of the universe U, cosmological constant Λ, the curvature of space k, energy density ρΛe, age of the universe tΩ etc. The development of the state equation highlights the importance of not neglecting any of the differential terms given the very large amounts in play that can counterbalance the infinitesimals. Some assumptions were put forth in order to solve these equations. The current version of the model partially explains several of the observed phenomena that raise questions. Numerical application of the model has yielded the following results, among others: Initially, during the Planck era, at the very beginning of Planck time, tp, the universe contained a single photon at Planck temperature TP, almost Planck energy EP in the Planck volume. During the photon inflation phase (before characteristic time ~10-9 [s]), the number of original photons (alphatons) increased at each unit of Planck time tp and geometrical progression~n3, where n is the quotient of cosmic time over Planck time t/tp. Then, the primordial number of photons reached a maximum of N~1089, where it remained constant. These primordial photons (alphatons) are still present today and represent the essential of the energy contained in the universe via the cosmological constant expressed in the form of energy EΛ. Such geometric growth in the number of photons can bring a solution to the horizon problem through γγ exchange and a photon energy volume that is in phase with that of the volume energy of the universe. The predicted total mass (p, n, e, and ν), based on the Maxwell-Juttner relativistic statistical distribution, is ~7 × 1050 [kg]. The predicted cosmic neutrino mass is ≤8.69 × 10-32 [kg] (≤48.7 [keV·c-2]) if based on observations of SN1987A. The temperature variation of the cosmic microwave background (CMB), as measured by Planck, can be said to be partially due to energy variations in the universe (ΔU/U) during the primordial baryon synthesis (energy jump from the creation of protons and neutrons).

The present paper is devoted to reconstruction and cosmological study in modified F(G) theory of gravity. Our reconstruction scheme is based on Friedmann metric induced equations in modified F(G) theory by supposing a power law form for the scale factor of Friedmann metric. Firstly, we deal with the stability study, the obtained model. This survey reveals that for appropriated choice of the reconstructed model parameter, this model is stable under two cosmological evolutions namely the de Sitter and the power law evolutions symbolized by the appropriated scale factor. Secondly, we investigate the inflationary survey by fitting the model with the inflation observables. These observables are determined and their comparison with Planck’s results leads to a special inflationary F(G) model. We prove that this model especially obtained for radiation domination evolution develops an instability, so can fall to ordinary matter domination era or dark energy domination era. This is the key of graceful exit from inflation.

First, we do a Taylor series expansion of Entropy. Afterwards we define the arrow of time. After that, we define what terms we will analyze in the Taylor series expansion of entropy to help in finding initial conditions which may allow for the earliest possible identification of the Arrow of Time in cosmology. Definition of the arrow of time will allow choosing different initial starting points. That is, that in the actual equations of classical GR, there is no reason to have time asymmetry after given initial conditions. Time asymmetry is built into initial conditions and we start to explore which initial conditions may assist in evaluating contributions to Entropy via an analysis of which terms in a Taylor series survive, and what their sign and contribution values are.

The cosmological implications of the Covariant Canonical Gauge Theory of Gravity (CCGG) are investigated. CCGG is a Palatini theory derived from first principles using the canonical transformation formalism in the covariant Hamiltonian formulation. The Einstein-Hilbert theory is thereby extended by a quadratic Riemann-Cartan term in the Lagrangian. Moreover, the requirement of covariant conservation of the stress-energy tensor leads to necessary presence of torsion. In the Friedman universe that promotes the cosmological constant to a time-dependent function, and gives rise to a geometrical correction with the EOS of dark radiation. The resulting cosmology, compatible with the $\Lambda$CDM parameter set, encompasses bounce and bang scenarios with graceful exits into the late dark energy era. Testing those scenarios against low-z observations shows that CCGG is a viable theory., Comment: Contribution to the International Workshop IWARA on Astronomy and Relativistic Astrophysics, September 2020. Accepted for publication in the Astronomische Nachrichten 2021; 8 pages, 6 figures

In the late 1970s the big bang model of cosmology was widely accepted and interpreted as implying the universe had a beginning. At the end of that decade William Lane Craig revived an argument for God known as the Kalam Cosmological Argument (KCA) based on this scientific consensus. Furthermore, he linked the big bang to the supposed biblical concept of creation ex nihilo found in Genesis. I shall critique Craig's position as expressed in a more recent update and argue that contemporary cosmology no longer understands the big bang as the ultimate beginning, seriously undermining the KCA. I will further contend that book of Genesis should not be understood as describing creation ex nihilo anyway.

We study M-theory compactified on twisted 7-tori with $G_2$-holonomy. The effective 4d supergravity has 7 chiral multiplets, each with a unit logarithmic K\"ahler potential. We propose octonion, Fano plane based superpotentials, codifying the error correcting Hamming (7,4) code. The corresponding 7-moduli models have Minkowski vacua with one flat direction. We also propose superpotentials based on octonions/error correcting codes for Minkowski vacua models with two flat directions. We update phenomenological $\alpha$-attractor models of inflation with $3\alpha=7,6,5,4,3,1$, based on inflation along these flat directions. These inflationary models reproduce the benchmark targets for detecting B-modes, predicting 7 different values of $r = 12\alpha/N_{e}^{2}$ in the range $10^{-2}\gtrsim r \gtrsim 10^{-3}$, to be explored by future cosmological observations., Comment: 63 pages, 25 figures, v2: comments added, typos fixed, v3: improved formulation presented in Sec.7 and refs added. The new formulation does not change inflationary predictions, but the potentials for decoupled heavy modes are simplified compared with the ones in the previous versions

The black hole (b.h.) model based on the strong field treatment of the Newton potential is presented. The essential role of self energy both at the Planck level and for matter and radiation at later stages supports the picture of an expanding Universe necessarily accompanied by particle creation if energy conservation applies at every scale. This process is shown to provide a gravitational repulsive force which can counterbalance gravitational attraction thus allowing the possibility of a steady expansion. This black hole treatment of our Universe evolution, questions the necessity of inflation. The role of the critical density to dictate the fate of the Universe is replaced by the black hole condition which entails a different relation between Hubble parameter and density thus disposing of dark energy. Since its predictions provide a different time development of the Universe also the evidence for its acceleration is disputed. That seems to provide a coherent scheme for our picture of the Universe evolution, based on Hubble’s law and backed up by the consideration of inertial forces. Newtonian angular momentum is also not conserved at cosmological scales. Finally we consider two coordinates systems. The conformally flat coordinates are shown to disprove inflation and the relevance of the Painleve-Gullstrand metric in providing global coordinates is underlined. The combined effect of Hubble expansion and of proper time also questions the existence of missing mass.

It is agreed that before the creation of particles, space was completely devoid of matter and radiation. In this study, we assume that the absolute void comprises 4 dimensions, namely 3 spatial dimensions and a force equivalent representing the factor of change among the elementary dimensions. Our hypothesis is based on the expansion of the spatial dimensions and the subsequent space instability. We demonstrated that when the equivalent outward force strength exceeds a critical limit, it collapses inwardly to restore the equilibrium of the system. Subsequently, the void inside the collapsed force equivalent acts as a void in a confined system, and the energy of the system remains conserved at all stages. With the decrease in the spatial dimensions owing to the collapse, the energy density increases, and at the final stage, the energy in the confined system becomes concentrated, thereby forming a solid state of energy. In this solid state of energy, a particle becomes the source of the elementary particles. The created high-energy sources are controlled by the internal and external forces of the source and all the entities in its external force field until equilibrium is reached. This article gives a summary of the Big Bang theory and its problems, which are further discussed in detail. This article will help in understanding how elementary dimensions play a role in the formation of elementary particles. Quark-gluon plasma, inflation, gravitational collapse, and gravitational lensing provide evidence that supports the elementary dimensions theory presented in this paper.

The NANOGrav pulsar timing array experiment reported evidence for a stochastic common-spectrum process affecting pulsar timing residuals in its 12.5-year dataset, which might be interpreted as the first detection of a stochastic gravitational wave background (SGWB). I examine whether the NANOGrav signal might be explained by an inflationary SGWB, focusing on the implications for the tensor spectral index $n_T$ and the tensor-to-scalar ratio $r$. Explaining NANOGrav while complying with upper limits on $r$ from BICEP2/Keck Array and Planck requires $r \gtrsim {\cal O}(10^{-6})$ in conjunction with an extremely blue tensor spectrum, $0.7 \lesssim n_T \lesssim 1.3$. After discussing models which can realize such a blue spectrum, I show that this region of parameter space can be brought in agreement with Big Bang Nucleosynthesis constraints for a sufficiently low reheating scale, $T_{\rm rh} \lesssim 100\,{\rm GeV}-1\,{\rm TeV}$. With the important caveat of having assumed a power-law parametrization for the primordial tensor spectrum, an inflationary interpretation of the NANOGrav signal is therefore not excluded., 5 pages, 2 figures. v2: revised conclusions, NANOGrav can in principle be due to an inflationary SGWB provided the reheating temperature is sufficiently (=very) low. References added, version accepted for publication in MNRAS Letters. Comments are welcome

The recent observations from CMB have imposed a very stringent upper-limit on the tensor/scalar ratio $r$ of inflation models, $r < 0.064$, which indicates that the primordial gravitational waves (PGW), even though possible to be detected, should have a power spectrum of a tiny amplitude. However, current experiments on PGW is ambitious to detect such a signal by improving the accuracy to an even higher level. Whatever their results are, it will give us much information about the early Universe, not only from the astrophysical side but also from the theoretical side, such as model building for the early Universe. In this paper, we are interested in analyzing what kind of inflation models can be favored by future observations, starting with a kind of general action offered by the effective field theory (EFT) approach. We show a general form of $r$ that can be reduced to various models, and more importantly, we show how the accuracy of future observations can put constraints on model parameters by plotting the contours in their parameter spaces., 19 pages, 9 figures with title changed and contents improved

We propose a novel explanation for the smallness of the observed cosmological constant (CC). Regions of space with a large CC are short lived and are dynamically driven to crunch soon after the end of inflation. Conversely, regions with a small CC are metastable and long lived and are the only ones to survive until late times. While the mechanism assumes many domains with different CC values, it does not result in eternal inflation nor does it require a long period of inflation to populate them. We present a concrete dynamical model, based on a super-cooled first order phase transition in a hidden conformal sector, that may successfully implement such a crunching mechanism. We find that the mechanism can only solve the CC problem up to the weak scale, above which new physics, such as supersymmetry, is needed to solve the CC problem all the way to the UV cutoff scale. The absence of experimental evidence for such new physics already implies a mild little hierarchy problem for the CC. Curiously, in this approach the weak scale arises as the geometric mean of the temperature in our universe today and the Planck scale, hinting at a new “CC miracle”, motivating new physics at the weak scale independent of electroweak physics. We further predict the presence of new relativistic degrees of freedom in the CFT that should be visible in the next round of CMB experiments. Our mechanism is therefore predictive and experimentally falsifiable.

Based on Dirac’s negative energy, we propose and study the negative matter. Bondi’s results are wrong. First, the negative matter can be the simplest model of unified dark matter and dark energy. Next, we discuss various possible theories of the negative matter: some field equations, similar electrodynamics, field equations with non-symmetry, etc. Third, the quantum theory of negative matter is researched. Matter surrounded by dark-negative matter corresponds to an infinitely deep potential trap in quantum mechanics and forms a base of the universal wave-particle duality and quantum mechanics. Fourth, we propose the mechanism of inflation as the origin of positive-negative matters created from nothing. Fifth, assume that dark matter is completely the negative matter, and we may calculate an evolutional ratio between total matter and usual matter from 1 of inflation and the radiation-dominated universe to 7.88 of the present matter-dominated universe. It agrees with the observed value 6.36~7. Sixth, we research the relativity of the negative matter and theory in Lobachevskian geometry. Seventh, we propose a judgment test of the negative matter as dark matter is opposite repulsive lensing and other eight possible tests. Eighty, we propose a figure on the unification of the four basic interactions in three-dimensional space, in which the “running” coupling constants of strong and weak interactions transform each other. The negative matter as a candidate of unification of dark matter and dark energy is not only the simplest, and may explain inflation and be calculated and tested.

We study the production of massive gauge bosons during inflation from the axion-type coupling to the inflaton and the corresponding oscillatory features in the primordial non-Gaussianity. In a window in which both the gauge boson mass and the chemical potential are large, the signal is potentially reachable by near-future large scale structure probes. This scenario covers a new region in oscillation frequency which is not populated by previously known cosmological collider models. We also demonstrate how to properly include the exponential factor and discuss the subtleties in obtaining power dependence of the gauge boson mass in the signal estimate., 25 pages

Within the framework of the general theory of relativity, an anisotropic cosmological model with expansion and rotation with a Bianchi type IX metric is constructed. The first stage of inflation of a Universe filled with a scalar field and an anisotropic liquid is considered. The Wheeler–De Witt equation is obtained, and the possibility of minisuperspace quantization is investigated.