parametic equations

it’s amazing that everyone i know thinks or stalwartly assumes i have my shit together and am by all means a functional mature human being

when really i feel like all i do is perfect my coping mechanisms and gross ups and downs into a weirdly rigid regimen and equations and parameters

arxiv.org
[1601.06324] Nuclear charge and neutron radii and nuclear matter: trend analysis

[ Authors ]
P.-G. Reinhard, W. Nazarewicz
[ Abstract ]
Radii of charge and neutron distributions are fundamental nuclear properties. They depend on both nuclear interaction parameters related to the equation of state of infinite nuclear matter and on quantal shell effects, which are strongly impacted by the presence of nuclear surface. In this work, by studying the dependence of charge and neutron radii, and neutron skin, on nuclear matter parameters, we assess different mechanisms that drive nuclear sizes. We apply nuclear density functional theory using a family of Skyrme functionals obtained by means of different optimization protocols targeting specific nuclear properties. By performing the Monte-Carlo sampling of reasonable functionals around the optimal parametrization, we study correlations between nuclear matter paramaters and observables characterizing charge and neutron distributions. We demonstrate the existence of the strong converse relation between the nuclear charge radii and the saturation density of symmetric nuclear matter and also between the neutron skins and the slope of the symmetry energy. For functionals optimized to experimental binding energies only, proton and neutron radii are weakly correlated due to canceling trends from different nuclear matter parameters. We show that by requiring that the nuclear functional reproduces the empirical saturation point of symmetric nuclear matter practically fixes the charge (or proton) radii, and vice versa. The neutron skin uncertainty primarily depends on the slope of the symmetry energy. Consequently, imposing a constraint on both $\rho_0$ and $L$ practically determines the nuclear size, modulo small variations due to shell effects.

arxiv.org
[1601.06734] Cosmology in new gravitational scalar-tensor theories

[ Authors ]
Emmanuel N. Saridakis, Minas Tsoukalas
[ Abstract ]
We investigate the cosmological applications of new gravitational scalar-tensor theories, which are novel modifications of gravity possessing 2+2 propagating degrees of freedom, arising from a Lagrangian that includes the Ricci scalar and its first and second derivatives. Extracting the field equations we obtain an effective dark energy sector that consists of both extra scalar degrees of freedom, and we determine various observables. We analyze two specific models and we obtain a cosmological behavior in agreement with observations, i.e. transition from matter to dark energy era, with the onset of cosmic acceleration. Additionally, for a particular range of the model parameters, the equation-of-state parameter of the effective dark energy sector can exhibit the phantom-divide crossing. These features reveal the capabilities of these theories, since they arise solely from the novel, higher-derivative terms.

arxiv.org
[1602.01772] Dark Energy and Dark Matter from Yang-Mills Condensate and the Peccei-Quinn mechanism

[ Authors ]
Andrea Addazi, Pietro Donà, Antonino Marcianò
[ Abstract ]
The idea that Dark Energy originates from a Yang-Mills condensate has been so far instantiated relying on the asymptotically-free perturbative expansion of SU(N) gauge-theories. This procedure is more appropriate in the ultra-violet regime than in the infrared limit, since SU(N) Yang-Mills theories generically show confinement. We approach the problem from the point of view of the functional renormalization group, and ground our study on the properties of the effective Lagrangian, to be determined non-perturbatively. Under very mild assumptions, some of us \cite{Dona:2015xia} have shown that if the effective Lagrangian has a minimum in the order parameter, YMC with equation of state $w_{\rm YMC} =-1$ actually originates in the infrared limit. At large redshift, the YMC Dark Energy has an evolution governed by a radiation-like equation of state parameter, i.e. $w_{\rm YMC} \rightarrow 1/3$, while at most recent redshift, the universe evolves asymptotically towards an accelerated de Sitter phase. In the contest of $G_{SM}\times SU(2)_{D}\times U(1)_{PQ}$, we also consider YMC interactions with QCD axions. We predict a transfer of Dark Energy density into Dark Matter density in a cosmological time that can be tested in the next generation of experiments dedicated to Dark Energy measures.

arxiv.org
[1601.07475] Spontaneous Scalarization with Massive Fields

[ Authors ]
Fethi M. Ramazanoğlu, Frans Pretorius
[ Abstract ]
We study the effect of a mass term in the spontaneous scalarization of neutron stars, for a wide range of scalar field parameters and neutron star equations of state. Even though massless scalars have been the focus of interest in spontaneous scalarization so far, recent observations of binary systems rule out most of their interesting parameter space. We point out that adding a mass term to the scalar field potential is a natural extension to the model that avoids these observational bounds if the Compton wavelength of the scalar is small compared to the binary separation. Our model is formally similar to the asymmetron scenario recently introduced in application to cosmology, though here we are interested in consequences for neutron stars and thus consider a mass term that does not modify the geometry on cosmological scales. We review the allowed values for the mass and scalarization parameters in the theory given current binary system observations and black hole spin measurements. We show that within the allowed ranges, spontaneous scalarization can have nonperturbative, strong effects that may lead to observable signatures in binary neutron star or black hole-neutron star mergers, or even in isolated neutron stars.