ترغب بنشر مسار تعليمي؟ اضغط هنا

Unifying Dark Matter and Dark Energy with non-Canonical Scalars

266   0   0.0 ( 0 )
 نشر من قبل Swagat Saurav Mishra
 تاريخ النشر 2018
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

Non-canonical scalar fields with the Lagrangian ${cal L} = X^alpha - V(phi)$, possess the attractive property that the speed of sound, $c_s^{2} = (2,alpha - 1)^{-1}$, can be exceedingly small for large values of $alpha$. This allows a non-canonical field to cluster and behave like warm/cold dark matter on small scales. We demonstrate that simple potentials including $V = V_0coth^2{phi}$ and a Starobinsky-type potential can unify dark matter and dark energy. Cascading dark energy, in which the potential cascades to lower values in a series of discrete steps, can also work as a unified model. In all of these models the kinetic term $X^alpha$ plays the role of dark matter, while the potential term $V(phi)$ plays the role of dark energy.



قيم البحث

اقرأ أيضاً

Recently, Kallosh and Linde have drawn attention to a new family of superconformal inflationary potentials, subsequently called $alpha$-attractors. The $alpha$-attractor family can interpolate between a large class of inflationary models. It also has an important theoretical underpinning within the framework of supergravity. We demonstrate that the $alpha$-attractors have an even wider appeal since they may describe dark matter and perhaps even dark energy. The dark matter associated with the $alpha$-attractors, which we call $alpha$-dark matter ($alpha$DM), shares many of the attractive features of fuzzy dark matter, with $V(varphi) = frac{1}{2}m^2varphi^2$, while having none of its drawbacks. Like fuzzy dark matter, $alpha$DM can have a large Jeans length which could resolve the cusp-core and substructure problems faced by standard cold dark matter. $alpha$DM also has an appealing tracker property which enables it to converge to the late-time dark matter asymptote, $langle wrangle simeq 0$, from a wide range of initial conditions. It thus avoids the enormous fine-tuning problems faced by the $m^2varphi^2$ potential in describing dark matter.
We study the interaction, in general curved spacetime, between a spinor and a scalar field describing dark energy; the so-called DE$_{ u}$ model in curved space. The dominant term is the dimension 5 operator, which results in different energy shifts for the neutrino states: an Aharonov-Bohm-like effect. We study the phenomenology of this term and make observational predictions to detect dark energy interactions in the laboratory due to its effect on neutrino oscillation experiments, which opens up the possibility of designing underground experiments to detect dark energy. This dimension 5 operator beyond the Standard Model interaction is less suppressed than the widely discussed dimension 6 operator, which corresponds to mass varying neutrinos; the dimension 5 operator does not suffer from gravitational instabilities.
Phenomenological implications of the Mimetic Tensor-Vector-Scalar theory (MiTeVeS) are studied. The theory is an extension of the vector field model of mimetic dark matter, where a scalar field is also incorporated, and it is known to be free from gh ost instability. In the absence of interactions between the scalar field and the vector field, the obtained cosmological solution corresponds to the General theory of Relativity (GR) with a minimally-coupled scalar field. However, including an interaction term between the scalar field and the vector field yields interesting dynamics. There is a shift symmetry for the scalar field with a flat potential, and the conserved Noether current, which is associated with the symmetry, behaves as a dark matter component. Consequently, the solution contains a cosmological constant, dark matter and a stiff matter fluid. Breaking the shift symmetry with a non-flat potential gives a natural interaction between dark energy and dark matter.
The recent observation of the the gravitational wave event GW170817 and of its electromagnetic counterpart GRB170817A, from a binary neutron star merger, has established that the speed of gravitational waves deviates from the speed of light by less t han one part in $10^{15}$. As a consequence, many extensions of General Relativity are inevitably ruled out. Among these we find the most relevant sectors of Horndeski gravity. In its original formulation, mimetic gravity is able to mimic cosmological dark matter, has tensorial perturbations that travel exactly at the speed of light but has vanishing scalar perturbations and this fact persists if we combine mimetic with Horndeski gravity. In this work, we show that implementing the mimetic gravity action with higher-order terms that break the Horndeski structure yields a cosmological model that satisfies the constraint on the speed of gravitational waves and mimics both dark energy and dark matter with a non-vanishing speed of sound. In this way, we are able to reproduce the $Lambda$CDM cosmological model without introducing particle cold dark matter.
125 - O. Sergijenko 2018
We generalize quintom to include the tachyonic kinetic term along with the classical one. For such a model we obtain the expressions for energy density and pressure. For the spatially flat, homogeneous and isotropic Universe with Friedmann-Robertson- Walker metric of 4-space we derive the equations of motion for the fields. We discuss in detail the reconstruction of the scalar fields potential $U(phi,xi)$. Such a reconstruction cannot be done unambiguously, so we consider 3 simplest forms of $U(phi,xi)$: the product of $Phi(phi)$ and $Xi(xi)$, the sum of $Phi(phi)$ and $Xi(xi)$ and this sum to the $kappa$th power.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا