arXiv subjects

Tonatiuh Matos

Publications and source records attributed to Tonatiuh Matos.

At least 55 records · Page 3Linked to original sources

arXiv2022

The cosmic microwave background and mass power spectrum profiles for a novel and efficient model of dark energy

In a previous work it was shown that by considering the quantum nature of the gravitational field mediator, it is possible to introduce the momentum energy of the graviton into the Einstein equations as an effective cosmological constant. The Compton Mass Dark Energy (CMaDE) model proposes that this momentum can be interpreted as dark energy, with a Compton wavelength given by the size of the observable universe $R_H$, implying that the dark energy varies depending on this size. The main result of this previous work is the existence of an effective cosmological constant $Λ=2π^2/λ^2$ that varies very slowly, being $λ=(c/H_0) R_H$ the graviton Compton wavelength. In the present work we use that the dark energy density parameter is given by $Ω_Λ=2π^2/3/R_H^2$, it only has the curvature $Ω_k$ as a free constant and depends exclusively on the radiation density parameter $Ω_r$. Using $Ω_{0r} = 9.54\times10^{- 5}$, the theoretical prediction for a flat universe of the dark energy density parameter is $Ω_{0Λ} = 0.6922$. We perform a general study for a non-flat universe, using the Planck data and a modified version of the CLASS code we find an excellent concordance with the Cosmic Microwave Background and Mass Power Spectrum profiles, provided that the Hubble parameter today is $H_0 = 72.6$ km/s/Mpc for an universe with curvature $Ω_{0k}=-0.003$. We conclude that the CMaDE model provides a natural explanation for the accelerated expansion and the coincidence problem of the universe.

physics.gen-ph↗

arXiv2021

Inflationary Cosmology: From Theory to Observations

The main aim of this paper is to provide a qualitative introduction to the cosmic inflation and its relationship with current cosmological observations. The inflationary model solves many of the fundamental problems that challenge the Standard Big Bang cosmology i.e. Flatness, Horizon and Monopole problem, and additionally provides an explanation for the initial conditions observed throughout the Large-Scale Structure of the Universe, such as galaxies. In this review we describe the general solutions carry out by a single scalar field. Then with the use of current surveys, we show the constraints imposed on the inflationary parameters $(n_{\rm s},r)$ which allow us to make the connection between theoretical and observational cosmology. In this way, with the latest results, it is possible to choose or at least to constrain the right inflationary model, parameterised by a single scalar field potential $V(ϕ)$.

astro-ph.CO↗

arXiv2021

The graviton Compton mass as Dark energy

One of the greatest challenges of science is to understand the current accelerated expansion of the Universe. In this work, we show that by considering the quantum nature of the gravitational field, its wavelength can be associated with an effective Compton mass. We propose that this mass can be interpreted as dark energy, with a Compton wavelength given by the size of the observable Universe, implying that the dark energy varies depending on this size. If we do so, we find that: 1.- Even without any free constant for dark energy, the evolution of the Hubble parameter is exactly the same as for the LCDM model, so we expect this model to have the same predictions as LCDM. 2.- The density rate of the dark energy is $Ω_Λ= 0.69$ which is a very similar value as the one found by the Planck satellite $Ω_Λ= 0.684$. 3.- The dark energy has this value because it corresponds to the actual size of the radius of the Universe, thus the coincidence problem has a very natural explanation. 4.-It is possible to find also a natural explanation to why observations inferred from the local distance ladder find the value $H_0= 73$ km/s/Mpc for the Hubble constant. We show that if we take the variability of the dark energy into account, they should measure $H_0= 67.3$ km/s/Mpc as well. 5.-In this model the inflationary period contains a natural successful graceful exit.

physics.gen-ph↗

arXiv2021

Weak gravitational quantum effects in boson particles

We rewrite the Klein-Gordon (KG) equation in an arbitrary space-time transforming it into a generalized Schrödinger equation. Then we take the weak field limit and show that this equation has some differences with the traditional Schrödinger equation plus a gravitational field. Thus, this procedure shows that the Schrödinger equation derived in a covariant manner is different from the traditional one. With this new Schrödinger equation, we study the KG equation in a Newtonian space-time to describe the behavior of a scalar particle in an inertial system. We give some examples where it is possible to study the energy levels, effective potential and the wave function of the systems, these results contain the gravitational effects due to the curvature of space-time. We show that it is possible to verify experimentally these effects in a laboratory using non-inertial reference frames.

gr-qc↗

arXiv2021

Gravitational perturbations in the Newman-Penrose formalism: Applications to wormholes

In this work we study the problem of linear stability of gravitational perturbations in stationary and spherically symmetric wormholes. For this purpose, we employ the Newman-Penrose formalism which is well-suited for treating gravitational radiation in General Relativity, as well as the geometrical aspect of this theory. With this method we obtain a "master equation" that describes the behavior of gravitational perturbations that are of odd-parity in the Regge-Wheeler gauge. This equation is later applied to a specific class of Morris-Thorne wormholes and also to the metric of an asymptotically flat scalar field wormhole. The analysis of the equations that these space-times yield reveals that there are no unstable vibrational modes generated by the type of perturbations here studied.

gr-qc↗

arXiv2021

Core-Halo Mass Relation in Scalar Field Dark Matter Models and its Consequences for the Formation of Supermassive Black Holes

Scalar-field dark matter (SFDM) halos exhibit a core-envelope structure with soliton-like cores and CDM-like envelopes. Simulations without self-interaction (free-field case) report a core-halo mass relation $M_c\propto M_{h}^β$, with either $β=1/3$ or $β=5/9$, which can be understood if core and halo obey certain energy or velocity scalings. We extend the core-halo mass relations to include SFDM with self-interaction (SI), either repulsive or attractive, and investigate its implications for the gravitational instability and collapse of solitonic cores, leading to supermassive black hole (SMBH) formation. For SFDM parameters that make $\sim$ Kpc-sized cores and CDM-like structure formation on large scales but suppressed on small scales, cores are stable for all galactic halos of interest, from the free-field to the repulsive SI limit. For attractive SI, however, halos masses $M_h\sim (10^{10}-10^{12}) M_\odot$ have cores that collapse to SMBHs with $M_{SMBH}\sim 10^{6}-10^8 M_\odot$, as observations seem to require, while smaller-mass halos have stable cores, for particle masses $m\simeq (2.14\times 10^{-22}-9.9\times 10^{-20})\rm{eV}/c^2$, if the free-field has $β=1/3$, or $m = 2.23\times 10^{-21}-1.7\times 10^{-18}\rm{eV}/c^2$, if $β=5/9$. For free-field and repulsive cases, however, if previous constraints on particle parameters are relaxed to allow much smaller (sub-galactic scale) cores, then halos can also form SMBHs, for the same range of halo and BH masses, as long as $β= 5/9$ is correct for the free-field. In that case, structure formation in SFDM would be largely indistinguishable from Cold Dark Matter (CDM). Such SFDM models might not resolve the small-scale structure problems of CDM, but they would explain the formation of SMBHs quite naturally. Since CDM, itself, has not yet been ruled out, such SFDM models must also be viable (Abbreviated).

astro-ph.GA↗

arXiv2021

Scalar field dark matter as an alternative explanation for the anisotropic distribution of satellite galaxies

In recent years, the scalar field dark matter (SFDM), also called ultralight bosonic dark matter, has received considerable attention due to the number of problems it might help to solve. Among these are the cusp-core problem and the abundance of small structures of the standard cold dark matter (CDM) model. In this paper we show that multi-state solutions of the low energy and weak gravitational field limit of field equations, interpreted as galactic halo density profiles, can provide a possible explanation to the anisotropic distribution of satellite galaxies observed in the Milky Way, M31 and Centaurus A, where satellites trajectories seem to concentrate on planes close to the poles of the galaxies instead of following homogeneously distributed trajectories. The core hypothesis is that multi-state solutions of the equations describing the dynamics of this dark matter candidate, namely, the Gross-Pitaevskii-Poisson equations, with monopolar and dipolar contributions, can possibly explain the anisotropy of satellite trajectories. In order to construct a proof of concept, we study the trajectories of a number of test particles traveling on top of the gravitational potential due to a multi-state halo with modes (1,0,0)+(2,1,0). The result is that particles accumulate asymptotically in time on planes passing close to the poles. Satellite galaxies are not test particles but interpreted as such, our results indicate that in the asymptotic time their trajectories do not distribute isotropically, instead they prefer to have orbital poles accumulating near the equatorial plane of the multistate halo. The concentration of orbital poles depends on whether the potential is monopolar or dipolar dominated.

astro-ph.GA↗

arXiv2021

Rotation curves with the multistate Scalar Field Dark Matter model

We use the concept of co-added rotation curves of Salucci et al. to investigate the properties of axi-symmetric multistate Scalar Field Dark Matter halos in low surface brightness galaxies and dwarf disc galaxies. We fit their rotation curves in two-state configurations and we find that all of these can be well fitted with a particle mass $μ\sim (10^{-23} - 10^{-24})\rm{eV}/c^2$. Comparing our results with the standard cosmological model, the well-known $Λ$-cold dark matter, by using the Bayesian information criterion and the Akaike information criterion, we found that our two-state model seemed to be preferred.

astro-ph.GA↗

arXiv2021

Consequences for the Scalar Field Dark Matter model from The McGaugh Observed-Baryon Acceleration Correlation

Although the standard cosmological model, the so-called $Λ$ Cold Dark Matter ("$Λ$CDM"), appears to fit well observations at the cosmological level, it is well known that it possesses several inconsistencies at the galactic scales. In order to address the problems of the $Λ$CDM at small scales, alternative models have been proposed, among the most popular ones the proposal of dark matter in the Universe being made of ultra-light bosons is a strong candidate nowadays. At this work, we study through an analytical approach the consequences arising from confronting the SPARC catalogue observed-baryon acceleration correlation with the scalar field dark matter model. We carry out such analysis either considering the features of galactic haloes extracted from structure formation simulations either from considering the existence of other non-dark-matter elements in the whole system (such as baryons or a supermassive black hole). Specifically, we address a recent claim that the model is not capable of reproducing a constant surface density in the core in contrast to what observations suggest for a host of galaxies with different sizes and morphologies. In this direction, we show that this discrepancy can be alleviated once the contributions of no-dark-matter constituents in the whole galactic system are taken into account. Additionally, we find that a mass of $m \simeq 1.41 \times 10^{-22}\ eV/c^2$ is capable of reproducing all our findings and correctly adjusting the rotation curves coming from the Milky Way galaxy.

astro-ph.GA↗

arXiv2020

Geodesics near a curvature singularity of stationary and axially symmetric space-times

In this work we study the local behavior of geodesics in the neighborhood of a curvature singularity contained in stationary and axially symmetric space-times. Apart from these properties, the metrics we shall focus on will also be required to admit a quadratic first integral for their geodesics. In particular, we search for the conditions on the geometry of the space-time for which null and time-like geodesics can reach the singularity. These conditions are determined by the equations of motion of a freely-falling particle. We also analyze the possible existence of geodesics that do not become incomplete when encountering the singularity in their path. The results are stated as criteria that depend on the inverse metric tensor along with conserved quantities such as energy and angular momentum. As an example, the derived criteria are applied to the Plebanski-Demianski class of space-times. Lastly, we propose a line element that describes a wormhole whose curvature singularities are, according to our results, inaccessible to causal geodesics.

gr-qc↗

arXiv2019

Scalar Field Dark Matter Spectator During Inflation: The Effect of Self-interaction

Nowadays cosmological inflation is the most accepted mechanism to explain the primordial seeds that led to the structure formation observed in the Universe. Current observations are in well agreement to initial adiabatic conditions, which imply that single-scalar-field inflation may be enough to describe the early Universe. However, there are several scenarios where the existence of more than a single field could be relevant during this period, for instance, the situation where the so-called spectator is present. Within the spectator scenario we can find the possibility that an ultra-light scalar field dark matter candidate could coexist with the inflaton. In this work we study this possibility where the additional scalar field could be massive or self-interacting. We use isocurvature observations to constrain the free parameters of the model.

astro-ph.CO↗

arXiv2018

Wormhole Cosmic Censorship: An Analytical Proof

In this work we present an analytical proof of cosmic censorship in a Kerr-like phantom wormhole (WH) which contains a singularity that is not protected by an event horizon. We show that the naked singularity of this space-time is causally disconnected from the universe. To do so, we consider a slowly rotating limit and by means of the Hamilton-Jacobi theory separate the Hamiltonian of the geodesics into two polynomials. During this process we find a fourth conserved quantity. After examining the properties of these polynomials we conclude that the ring singularity is untouchable by any observer traveling in a geodesic of this space-time. We also derive the conditions on the four constants of motion that are necessary for a traveler to go back and forth both universes connected through the WH, and then compare its structure to that of a negative mass Kerr black hole.

gr-qc↗

arXiv2017

Rotation curves of high-resolution LSB and SPARC galaxies with fuzzy and multistate (ultra-light boson) scalar field dark matter

Cold dark matter (CDM) has shown to be an excellent candidate for the dark matter (DM) of the Universe at large scales, however it presents some challenges at the galactic level. The scalar field dark matter (SFDM), also called fuzzy, wave, Bose-Einstein condensate or ultra-light axion DM, is identical to CDM at cosmological scales but different at the galactic ones. SFDM forms core halos, it has a natural cut-off in its matter power spectrum and it predicts well-formed galaxies at high redshifts. In this work we reproduce the rotation curves of high-resolution low surface brightness (LSB) and SPARC galaxies with two SFDM profiles: (1)~The soliton+NFW profile in the fuzzy DM (FDM) model, arising empirically from cosmological simulations of real, non-interacting scalar field (SF) at zero temperature, and (2)~the multistate SFDM (mSFDM) profile, an exact solution to the Einstein-Klein-Gordon equations for a real, self-interacting SF, with finite temperature into the SF potential, introducing several quantum states as a realistic model for a SFDM halo. From the fits with the soliton+NFW profile, we obtained for the boson mass $0.212< m_ψ/(10^{-23} \mathrm{eV}/c^2)<27.0$ and for the core radius $0.326< r_c/\mathrm{kpc}<8.96$. From the combined analysis with the LSB galaxies, we obtained $m_ψ= 0.554 \times10^{-23}\mathrm{eV}$, a result in tension with the severe cosmological constraints. Also, we show the analytical mSFDM model fits the observations as well as or better than the empirical soliton+NFW profile, and it reproduces naturally the wiggles present in some galaxies, being a theoretically motivated framework additional or alternative to the FDM profile.

astro-ph.GA↗

arXiv2017

Comparison between two scalar field models using rotation curves of spiral galaxies

Scalar fields have been used as candidates for dark matter in the universe, from axions with masses $\sim10^{-5}$eV until ultra-light scalar fields with masses $\sim10^{-22}$eV. Axions behave as cold dark matter while the ultra-light scalar fields galaxies are Bose-Einstein condensate drops. The ultra-light scalar fields are also called scalar field dark matter model. In this work we study rotation curves for low surface brightness spiral galaxies using two scalar field models: the Gross-Pitaevskii Bose-Einstein condensate in the Thomas-Fermi approximation and a scalar field solution of the Klein-Gordon equation. We also used the zero disk approximation galaxy model where photometric data is not considered, only the scalar field dark matter model contribution to rotation curve is taken into account. From the best-fitting analysis of the galaxy catalog we use, we found the range of values of the fitting parameters: the length scale and the central density. The worst fitting results (values of $χ^2_{red}$ much greater than 1, on the average) were for the Thomas-Fermi models, i.e., the scalar field dark matter is better than the Thomas-Fermi approximation model to fit the rotation curves of the analysed galaxies. To complete our analysis we compute from the fitting parameters the mass of the scalar field models and two astrophysical quantities of interest, the dynamical dark matter mass within 300 pc and the characteristic central surface density of the dark matter models. We found that the value of the central mass within 300 pc is in agreement with previous reported results, that this mass is $\approx 10^{7}$ $M_\odot/$pc$^2$, independent of the dark matter model. And, on the contrary, the value of the characteristic central surface density do depend on the dark matter model.

astro-ph.GA↗

arXiv2017

Bose-Einstein Condensation and Symmetry Breaking of a Complex Charged Scalar Field

In this work the Klein-Gordon (KG) equation for a complex scalar field with U(1) symmetry endowed in a mexican-hat scalar field potential with thermal and electromagnetic contributions is written as a Gross-Pitaevskii (GP)-like equation. This equation is interpreted as a charged generalization of the GP equation at finite temperatures found in previous works. Its hydrodynamical representation is obtained and the corresponding thermodynamical properties are derived and related to measurable quantities. The condensation temperature in the non-relativistic regime associated with the aforementioned system within the semiclassical approximation is calculated. Also, a generalized equation for the conservation of energy for a charged bosonic gas is found when electromagnetic fields are introduced, and it is studied how under certain circumstances its breaking of symmetry can give some insight on the phase transition of the system not just into the condensed phase but also on other related systems.

cond-mat.quant-gas↗

arXiv2017

Scalar field dark matter in clusters of galaxies

One alternative to the cold dark matter (CDM) paradigm is the scalar field dark matter (SFDM) model, which assumes dark matter is a spin-0 ultra-light scalar field (SF) with a typical mass $m\sim10^{-22}\mathrm{eV}/c^2$ and positive self-interactions. Due to the ultra-light boson mass, the SFDM could form Bose-Einstein condensates (BEC) in the very early Universe, which are interpreted as the dark matter haloes. Although cosmologically the model behaves as CDM, they differ at small scales: SFDM naturally predicts fewer satellite haloes, cores in dwarf galaxies and the formation of massive galaxies at high redshifts. The ground state (or BEC) solution at zero temperature suffices to describe low-mass galaxies but fails for larger systems. A possible solution is adding finite-temperature corrections to the SF potential which allows combinations of excited states. In this work, we test the finite-temperature multistate SFDM solution at galaxy cluster scales and compare our results with the Navarro-Frenk-White (NFW) and BEC profiles. We achieve this by fitting the mass distribution of 13 \textit{Chandra} X-ray clusters of galaxies, excluding the region of the brightest cluster galaxy. We show that the SFDM model accurately describes the clusters' DM mass distributions offering an equivalent or better agreement than the NFW profile. The complete disagreement of the BEC model with the data is also shown. We conclude that the theoretically motivated multistate SFDM profile is an interesting alternative to empirical profiles and ad hoc fitting-functions that attempt to couple the asymptotic NFW decline with the inner core in SFDM.

astro-ph.CO↗

arXiv2017

On the Possibility that Ultra-Light Boson halos host and form Super-massive Black Holes

Several observations suggest the existence of super-massive black holes (SMBH) at the centers of giant galaxies. However the mechanism under which these objects form remains non completely understood. In this work we review an alternative mechanism of formation of galactic SMBHs. This is, the collapse of ultra-light scalar field configurations playing the role of dark matter halos. Several works have studied this scenario and investigated its plausibility. The theory of collapse of scalar field configurations into compact objects has been extensively studied regarding to boson stars, in this work we extrapolate such results for models of galactic halos hosting central SMBHs. We construct the simplest setup of an ultra-light scalar field configuration laying in a Schwarzschild space-time for modeling a galactic system with a SMBH in the quasi-static limit. This model is applicable to systems either out of their accretion-phase at late times or either for those undergoing into a very slow accretion-phase, such as some early-type giant elliptic galaxies and bulges. On the other hand, very recent direct observation of Sagittarius A by the Event Horizon Telescope will open an era of explorations of the deep-inner galactic region of the Milky Way that will enable us to test and distinguish various dark matter models. Thus we use our model to give a very first step towards that direction. We derive the stellar kinematics induced by this sort dark matter to obtain information of the black hole's influence into the observable features of the velocity field of visible matter deep inside the galaxy. Thus we compute the radial velocity, acceleration and velocity dispersion densities for some realistic cases.

gr-qc↗

arXiv2017

Pseudo Spectral Transform for Schrödinger--Poisson Equations

Here we present exact, stationary, parametric solutions to the Schrödinger--Poisson system. We confront two images: on one hand, we draw on the homotopy analysis method which leads us to a nonlinear integral scheme. Indeed, this approach might be simplified by looking for sufficiently smooth solutions vanishing asymptotically. However, since our system possesses stiffness an additional analysis has to be considered. On the other hand, we seek for exact solutions over the inverse scattering method by introducing a pseudo spectral transform. In fact, this pseudo spectral method generalises Korteweg--de Vries family's kernel and let us to circumvent some technical difficulties originally arisen in our first approach although, again, we come to an integral representation, which we test for convergence.

quant-ph↗