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Many models have been proposed to minimize the dark matter (DM) content in various astronomical objects at every scale in the Universe. The most widely known model is MOdified Newtonian dynamics (MOND). MOND was first published by Mordehai Milgrom in 1983. A second concurrent model is modified gravity, which is a covariant scalar-tensor-vector extension of general relativity. Other theories also exist but have not been broadly applied to a large list of astronomical objects. Eventually, we can also mention the Newtonian fractional-dimension gravity, a gravity theory based on spaces with fractional (i.e., noninteger) dimension. A new model, called [kappa]-model, based on very elementary phenomenological considerations, has recently been proposed in the astrophysics field. This model shows that the presence of DM can be considerably minimized with regard to the dynamics of galaxies. The [kappa]-model belongs to the general family of theories descended from MOND. Under this family of theories, there is no need to develop a highly uncertain DM sector of physics to explain the observations. Key words: dark matter, MOND, modified gravity, [kappa]-model, galaxies, galaxy clusters, 1. Introduction The dark matter (DM) paradigm is considered to simply explain the dynamics in individual galaxies and galaxy clusters. Astrophysicists have been searching for DM evidence for years. However, [...]

In this paper, we extend Shaposhnikov et al.'s parity violating the Einstein-Cartan-Holst action by adding to Holst term H, a Proca photon-torsion coupling [[chi].sub.pt] = [10.sup.-24] as computed by De Sabbata, Garcia de Andrade, and Sivaram. The strength of Holst term is obtained, in the case of early universe torsion as, T ~ 1 MeV. The gravity part is the Planck mass product with the Holst term. The photon mass in this case yields [m.sup.2.[gamma]] H ~ [10.sup.-69] Ge[V.sup.4]. Therefore, in this case, the photon interacts very weakly with spin-torsion matter in Einstein-Cartan (EC) gravity and the strength of the Maxwell-Proca-Holst interaction is much weaker than in the pure gravity sector. For dark photons, this situation changes drastically since a dark photon mass reaches 1.5 GeV, and from this mass and T = [10.sup.-3] GeV, one obtains a Maxwell-Proca-Holst strength of [10.sup.-6] Ge[V.sup.4], which is now comparable with the gravity sector. Dynamo mechanism competes with the chirality and dissipation by the handness of the magnetic field with respect to the torsion trace vector to regenerate the magnetic field decay. Bombacigno and Mantovani recently found a sign of the Immirzi parameter in the Holst-Nieh-Yan extension of EC gravity. Here, we also find torsion waves for the Immirzi inverse parameter in the sense that this divergence of torsion trace is porportional to the Immirzi field. Key words: torsion, spiral, Einstein-Cartan-Holst, parity, chiral, 1. Introduction Ryutov et al. [1] have considered how Maxwell-Proca electrodynamics corresponding to finite photon mass [2] cause a substantial change of Maxwell electromagnetic (EM) stress tensor and under certain [...]

In this work, to investigate the dynamical nature of the kinematic asymmetry in the isolated gas-rich dwarf irregular galaxy W LM in the Local Group, we consider that the dark matter halo and the disk do not have the same center of mass (i.e., the disk lies off-center in the potential of the extended dark matter halo), which is one of the possible physical explanations for the kinematic lopsidedness. To do so, we generate a lopsided halo potential by considering two dark matter mass density models, ISO and Burkert, and we add up the contribution to the rotation curve of a perturbation term [V.sub.1](R)cos[phi] in the gravitational potential, which arises from the offset between the disk and the dark matter halo. We show that such an m = 1 perturbation improves the rotation curve modeling when compared to a non-perturbed potential and the shape of the HI gas rotation curves is fitted better in the approaching side if the perturbation term in the halo potential is taken into account for this galaxy dynamics. In fact, displacing the disk center by 0.1 kpc from the halo center is sufficient to provide such an improvement in modeling the rotation curve. Key words: galaxy, kinematics and dynamics, structure, halo, dwarf. Afin etudier la nature dynamique de l'asymetrie cinematique dans la galaxie naine WLM irreguliere, isolee, riche en gaz et membre du groupe local, nous examinons ici l'idee que son halo de matiere noire et son disque n'ont pas le meme centre de masse, i.e. le disque est decentre par rapport au potentiel du halo de matiere noire etendue, ce qui est une des explications physiques possibles de l'asymetrie cinematique. A cette fin, nous generons un potentiel de halo asymetrique en considerant deux modeles pour la densite de masse de la matiere noire, ISO et Burkert et nous additionnons la contribution a la courbe de rotation du terme de perturbation [V.sub.1](R)cos[phi] dans le potentiel gravitationnel, qui provient de la separation entre le halo du disque et celui de la matiere noire. Nous montrons qu'une telle perturbation m = 1 ameliore la modelisation de la courbe de rotation, lorsque comparee au potentiel non perturbe, et qu'alors la forme des courbes de rotation du gaz HI est mieux ajustee numeriquement dans le cote d'approche si le terme de perturbation dans le potentiel du halo est pris en compte dans la dynamique de la galaxie. En fait, un deplacement du centre du disque de 0.1 kpc du centre du halo est suffisant pour produire un tel deplacement dans la modelisation des courbes de rotation. [Traduit par la Redaction] Mots-cles : galaxie, cinematique et dynamique, structure, halo, naine., 1. Introduction It is accepted that galaxies are surrounded by large dark matter halos, which are much more massive than the visible components of galaxies and dominate much of their [...]

In this paper, viscous cosmological dynamics are studied in the presence of dark matter Bose-Einstein condensation by curved-FRW background. For this purpose, we use the BEC regime rather than normal dark matter (cold dark matter or barotropic dark matter) with the dark matter equation of state as [p.sub.dm] [varies] [[rho].sup.2.sub.dm], which arises from the gravitational form. Therefore, we obtain the corresponding continuity equations with the existence of the universe components by considering an interacting model with modified Chaplygin gas. Afterward, we derive the energy density and the pressure of dark energy in terms of the redshift parameter. And then, by introducing a parametrization function and fitting it with 51 supernova data with the likelihood analysis, we find the cosmological parameters versus redshift parameter. In what follows, we plot the corresponding dynamic graphs proportional to redshift, and then we represent that the universe is currently undergoing an accelerated expansion phase. Finally, we explore the stability and the instability of the present model with the sound speed parameter. Key words: dark energy, dark matter, Bose-Einstein condensation, modified Chaplygin gas, bulk viscosity. Sur un fond cosmologique FRW courbe, nous etudions ici la dynamique cosmologique visqueuse, en presence de matiere noire resultant d'un condensat de Bose-Einstein. A cette fin, nous utilisons le regime CBE plutot que la matiere noire normale (la matiere noire froide ou barotrope), avec une equation d'etat de la matiere noire [p.sub.dm] [varies] [[rho].sup.2.sub.dm], qui est de forme gravitationnelle. En consequence, nous obtenons les equations de continuite correspondantes avec l'existence de composants d'univers en considerant un modele interactif avec gaz de Chaplygin modifie. Ensuite, nous derivons la densite d'energie et la pression de l'energie sombre en termes du parametre de decalage vers le rouge (spectral). C'est suivi de l'introduction d'une fonction de parametrage et par ajustage numerique avec les donnees de 51 supernovae et une analyse de vraisemblance, nous trouvons les parametres cosmologiques versus le parametre du decalage spectral. Dans ce qui suit, nous tracons les graphiques dynamiques correspondants proportionnels au decalage spectral, qui presentent l'univers couramment soumis a une phase d'expansion acceleree. Finalement, nous explorons la stabilite et l'instabilite du present modele a l'aide du parametre de la vitesse du son. [Traduit par la Redaction] Mots-cles : energie sombre, matiere noire, condensation de Bose-Einstein, gaz de Chaplygin modifie, viscosite volumique., 1. Introduction As we know, the contents of the universe are dark matter, dark energy, and visible matter, in which visible matter consists of the galaxies, stars, planets, and every [...]