Nonsingular bouncing cosmology from general relativity

**equation**-of-

**state**parameter which is different before and after the bounce. Expand abstract.

**of**classical nonsingular bouncing cosmology, which results from general relativity if we allow for degenerate metrics. The simplest model has a matter content with a constant

**equation**-of-

**state**parameter and we get the modified Hubble diagrams for both the luminosity distance and the angular diameter distance. Based on these results, we present a Gedankenexperiment to determine the length scale

**of**the spacetime defect which has replaced the big bang singularity. A possibly more realistic model has an

**equation**-of-

**state**parameter which is different before and after the bounce. This last model also provides an upper bound on the defect length scale.

4/10 relevant

arXiv

The Chaplygin gas as a model for modified teleparallel gravity?

**of**treating the exotic Chaplygin-gas (CG) fluid model as some manifestation

**of**an $f(T)$ gravitation. To this end, we use the different cosmological CG

**equations**

**of**state, compare them with the

**equation**

**of**

**state**for the modified teleparallel gravity and reconstruct the corresponding Lagrangian densities. We then explicitly derive the

**equation**

**of**

**state**parameter

**of**the torsion fluid $w_T$ and study its evolution for vacuum-torsion, radiation-torsion, dust-torsion, stiff fluid torsion, and radiation-dust-torsion multi-fluid systems. The obtained Lagrangians have, in general, matter dependence due to the matter-torsion coupling appearing in the energy density and pressure terms

**of**the modified teleparallel gravity theory. For the simplest CG models, however, it is possible to reconstruct $f(T)$ Lagrangians that depend explicitly on the torsion scalar $T$ only. The preliminary results show that, in addition to providing Chaplygin-gas-like solutions to the modified teleparallel gravitation, which naturally behave like dark matter and dark energy at early and late times respectively, the technique can be used to overcome some

**of**the challenges attributed to the CG cosmological alternative.

5/10 relevant

arXiv

Nuclear matter properties at finite temperatures from effective interactions

**equation**

**of**

**state**and the single-nucleon potential for nuclear matter at finite temperatures and compare them to those from the SCGF approach. Expand abstract.

**of**cold nuclear matter and

**of**finite nuclei, can properly describe the hot dense nuclear matter produced in intermediate-energy heavy-ion collisions. We use two representative effective interactions, i.e., an improved isospin- and momentum-dependent interaction with its isovector part calibrated by the results from the \emph{ab initio} non-perturbative self-consistent Green's function (SCGF) approach with chiral forces, and a Skyme-type interaction fitted to the

**equation**

**of**

**state**

**of**cold nuclear matter from chiral effective many-body perturbation theory and the binding energy

**of**finite nuclei. In the mean-field approximation, we evaluate the

**equation**

**of**

**state**and the single-nucleon potential for nuclear matter at finite temperatures and compare them to those from the SCGF approach. We find that the improved isospin- and momentum-dependent interaction reproduces reasonably well the SCGF results due to its weaker momentum dependence

**of**the mean-field potential than in the Skyrme-type interaction. Our study thus indicates that effective interactions with the correct momentum dependence

**of**the mean-filed potential can properly describe the properties

**of**hot dense nuclear matter and are thus suitable for use in transport models to study heavy-ion collisions at intermediate energies.

4/10 relevant

arXiv

Revisiting **equation** **of** **state** for white dwarfs within finite temperature
quantum field theory

**equation**

**of**

**state**of degenerate matter in the white dwarfs. Expand abstract.

**of**fine-structure constant on the

**equation**

**of**

**state**

**of**degenerate matter in the white dwarfs are computed in literature using non-relativistic considerations ab initio. Given special relativity plays a key role in the white dwarf physics, such computations are therefore unsatisfactory. After reviewing the existing literature, here we employ the techniques

**of**finite temperature relativistic quantum field theory to compute the

**equation**

**of**

**state**

**of**degenerate matter in the white dwarfs. In particular, we compute the leading order corrections due to the finite temperature and the fine-structure constant. We show that the fine-structure constant correction remains well-defined even in the non-relativistic regime in contrast to the existing treatment in the literature. Besides, it involves an apriori undetermined length scale characterizing the electron-nuclei interaction.

7/10 relevant

arXiv

Two-flavor chiral perturbation theory at nonzero isospin: Pion condensation at zero temperature

**equation**

**of**

**state**

**of**two-flavor finite isospin chiral perturbation theory at next-to-leading order in the pion-condensed phase at zero temperature. We show that the transition from the vacuum phase to a Bose-condensed phase is

**of**second order. While the tree-level result has been known for some time, surprisingly quantum effects have not yet been incorporated into the

**equation**

**of**

**state**. We find that the corrections to the quantities we compute, namely the isospin density, pressure, and

**equation**

**of**state, increase with increasing isospin chemical potential. We compare our results to recent lattice simulations

**of**2+1 flavor QCD with physical quark masses. The agreement with the lattice results is generally good and improves somewhat as we go from leading order to next-to-leading order in $\chi$PT.

7/10 relevant

arXiv

Implications of the mass $M=2.17^{+0.11}_{-0.10}$M$_\odot$ of PSR~J0740+6620 on the **Equation** **of** **State** of Super-Dense Neutron-Rich Nuclear Matter

**of**the very recently reported mass $M=2.17^{+0.11}_{-0.10}$M$_\odot$

**of**PSR~J0740+6620 on the

**Equation**

**of**

**State**(EOS)

**of**super-dense neutron-rich nuclear matter with respect to existing constraints on the EOS based on the mass $M=2.01\pm 0.04$M$_\odot$

**of**PSR~J0348+0432, the maximum tidal deformability

**of**GW170817 and earlier results

**of**various terrestrial nuclear laboratory experiments. The lower limit

**of**the skewness $J_0$ measuring the stiffness

**of**super-dense isospin-symmetric nuclear matter is raised raised from about -220 MeV to -150 MeV, reducing significantly its current uncertainty range. The lower bound

**of**the high-density symmetry energy also increases appreciably leading to a rise

**of**the minimum proton fraction in neutron stars at $\beta$-equilibrium from about 0 to 5\% around three times the saturation density

**of**nuclear matter. The difficulties for some

**of**the most widely used and previously well tested model EOSs to predict simultaneously both a maximum mass higher than 2.17 M$_\odot$ and a pressure consistent with that extracted from GW170817 present some interesting new challenges for nuclear theories.

4/10 relevant

arXiv

Superconductivity and **Equation** **of** **State** of Distorted fcc-Lanthanum above Megabar Pressures

**equation**

**of**

**state**: V(100)= 16.48(7) A^3, B(100)=208(26) GPa and B(100)'=9(1) in the range of 100-160 GPa. Expand abstract.

**of**the rare-earth series

**of**elements that has recently raised considerable interest due to its unique superhydride LaH10+{\delta} and its superconducting properties. Although several studies have found superconductivity and phase transitions in metallic La, there has been a lack

**of**experimental evidence for the

**equation**

**of**

**state**and superconductivity over one megabar pressure. Herein, we extend pressure range up to 163 GPa to explore the

**equation**

**of**

**state**and superconductivity

**of**La via electrical transport and X-ray diffraction measurements. Le Bail refinement

**of**experimental XRD patterns indicated that above 130 GPa orthorhombically distorted fcc-La(Fm3m-Fmmm) phase emerges with the fitted parameters

**of**3rd order Birch-Murnaghan

**equation**

**of**state: V(100)= 16.48(7) A^3, B(100)=208(26) GPa and B(100)'=9(1) in the range

**of**100-160 GPa. The superconductivity emerges in the newly distorted fcc-La with an onset critical temperature Tc

**of**6.1 K at 100 GPa, decreases to 1.5 K at 130 GPa, then begins to grow and reach 3.3 K at 150 GPa. We have extrapolated the upper critical magnetic field Hc as 0.32 T (Gingburg-Landau) and 0.43 T (WHH formalism) at 140 GPa. Ab initio calculations confirm electron-phonon coupling mechanism with predicted Tc(A-D)=2.2 K ({\mu}*=0.195), dTc/dP = 0.11-0.13 K/GPa and Hc=0.4 T and coherence length {\xi}(BCS)=28 nm at 140 GPa.

7/10 relevant

arXiv

Gravitational Merging as a Possible Source for the Cosmological Accelerating

**of**cosmic objects is regarded as a possible source

**of**the extra-acceleration

**of**the universe at large scale. The merging/clustering

**of**cosmic objects introduces a correction term in the

**equation**

**of**

**state**for the effective present cosmic fluid in the form

**of**$P=w\rho+b\rho^2$. As a result, an alternative relation for the energy density includes over and under-dense regions is obtained that coincide with the conventional relation in the standard limit. By analogy with bubbles, the under-dense regions (voids) in the cosmic fluid is shown to provide the needed negative pressure. Invoking the observational constraint for the dark energy

**equation**

**of**

**state**$w$, we show that the merging

**of**voids will act as a possible source

**of**extra-accelerating at large scale in comparison with non-merging cosmic gas.

4/10 relevant

arXiv

Burst particle creation in gravitational collapse to a horizonless compact object

**equations**

**of**

**state**. Expand abstract.

**of**radius very close to its horizon radius generally emits transient Hawking radiation followed by a couple

**of**bursts separated each other by a long time interval. In the current paper, we expand the previous work in two independent directions: changing boundary conditions and specifying the

**equations**

**of**

**state**

**of**the matter. First, we introduce a perfectly reflective surface collapsing to an ultracompact object and find that this model also emits transient Hawking radiation that is followed only by a single burst. Second, we introduce two different collapse dynamics to an ultracompact object and specify the corresponding matter

**equations**

**of**

**state**. We find that transient Hawking radiation is quite commonly seen in early times, while the subsequent bursts strongly depend on the boundary condition and the

**equation**

**of**

**state**or the braking behavior

**of**the surface.

7/10 relevant

arXiv

Fourier-series expansion of the dark-energy **equation** **of** **state**

**of**the universe still remains as a mystery, however, several papers based on observational data have shown that its

**equation**

**of**

**state**may have an oscillatory behaviour. In this paper, we provide a general description for the dark-energy

**equation**-of-

**state**$w(z)$ in the form

**of**Fourier series. This description generalises some previous dynamical dark energy models and is in agreement with the $w(z)$ reconstructions. We make use

**of**a modified version

**of**a simple and fast Markov Chain Monte Carlo code to constraint the model parameters. For the analysis we use data from supernovae type-Ia , baryon acoustic oscillations, $H(z)$ measurements and cosmic microwave background. We provide a comparison

**of**the proposed model with $\Lambda$CDM, $w$CDM and the standard Taylor approximation. The Fourier series expansion

**of**$w(z)$ is preferred from $\Lambda$CDM at more than $3\sigma$ significance level based on the improvement in the fit alone. We use the Akaike criteria to perform the model comparison and found that, even though there are extra parameters, there is a slight preference

**of**the Fourier series compared with the $\Lambda$CDM model. The preferred shape

**of**$w(z)$ found here puts in jeopardy the single scalar field models, as they as they cannot reproduce the crossing the phantom divide line $w=-1$.

6/10 relevant

arXiv