We propose two novel models in the framework of $f(Q)$ gravity to explain our accelerated universe, namely the exponential $f(Q)_{EXP}$ model and the hyperbolic tangent $f(Q)_{HT}$ model. The current cosmological electromagnetic observations including the cosmic microwave background anisotropies (CMB), the baryon acoustic oscillations(BAO), the type Ia supernovae (SN) and the direct measurements of H(z), combined with the simulated gravitational-wave data are used to constrain the $f(Q)$ models. We find that the Hubble tension can be significantly alleviated to $1.40\sigma$ level in the $f(Q)_{EXP}$ model. The fitting $\chi^2$ of the $f(Q)_{HT}$ model is $9.75\sigma$ poorer than that of the $f(Q)_{EXP}$ model, implying the $f(Q)_{HT}$ model would be excluded by future gravitational-wave observation.
In this paper, we present the spherically symmetric wormhole in Einstein's gravity coupling phantom field and nonlinear electromagnetic field. Numerical results show that this solution violates the Null Energy Condition (NEC), and as the parameters change, the ADM mass of the entire spacetime changes from positive to negative. In addition, we analyze the light ring (LR) of the solution and demonstrate the astronomical observation properties. Especially when negative mass appears, the general LR will not appear, only a ``special unstable LR" exists at the throat, which is caused by the repulsive effect of the negative mass on both sides of the wormhole. Finally, we draw the embedding diagram to reflect the geometric characteristics of the wormhole.
In this paper, we study the spherically symmetric traversable wormholes with a scalar field supported by a phantom field in the anti-de Sitter (AdS) asymptotic spacetime. Despite coupling the scalar matter field, these wormholes remain massless and symmetric for reflection of the radial coordinate $r \rightarrow -r$. The solution possesses a finite Noether charge $Q$, which varies as a function of frequency $\omega$ with changes in the cosmological constant $\Lambda$ and the throat size $r_0$. Under specific conditions, an approximate ``event horizon'' will appear at the throat.
We develop a symmetric traversable wormhole model, integrating Einstein's gravitational coupling phantom field and a nonlinear electromagnetic field. This work indicates the emergence of negative ADM mass within a specific parameter range, coinciding with distinct alterations in the wormhole's spacetime properties. Despite violating the Null Energy Condition (NEC) and other energy conditions, the solution exhibits unique characteristics in certain energy-momentum tensor components, potentially accounting for the manifestation of negative mass.
In this paper, we present the spherically symmetric Proca star in the presence of a phantom field and obtain a traversable wormhole solution for non-trivial topological spacetime. Using numerical methods, symmetric solutions and asymmetric solutions are obtained in two asymptotically flat regions. We find that when changing the throat size $r_{0}$, both the mass $M$ and the Noether charge $Q$ no longer have the spiral characteristics of an independent Proca star, furthermore, the asymmetric solution can be turned into the symmetric solution at some frequency $\omega$ in certain $r_{0}$. In particular, we find that when the frequency takes a certain value, for each solution, there is an extremely approximate black hole solution, and there is even a case where an event horizon appears on both sides of the wormhole throat.
In this paper, we study the spherically symmetric Dirac star model in the presence of a phantom field, obtaining a traversable wormhole solution in non-trivial topological spacetime. This solution exhibits asymmetry in both the field configuration and the metric and possesses a finite ADM mass $M$ and Noether charge $Q$. Furthermore, we find that due to the presence of a wormhole at the center, this solution exhibits many differences from the Dirac star under trivial spacetime. Notably, when the wormhole throat size is small, our numerical calculations indicate the emergence of an extremely approximate black hole solution on one side of the wormhole spacetime, a phenomenon unexplored. At this time, the Kretschmann scalar near the throat tends to infinity, indicating the wormhole becomes untraversable.
Observable scattering processes entail emission-absorption of soft photons. As these degrees of freedom go undetected, some information is lost. Whether some of this information can be recovered in the observation of the hard photons, depends of the actual pattern of the scrambling of information. We compute the information scrambling of photon scattering by the tripartite mutual information in terms of the 2-Renyi entropy, and find a finite amount of scrambling is present. The developed procedure thus sheds novel light on the black hole information loss paradox, showing that scrambling is a byproduct of decoherence achieved by the scattering system in its interaction with the environment, due to the emission-absorption of soft photons in fully unitary processes.
Black holes are a recently observed theoretical prediction of General Relativity, characterized by event horizons, from which information cannot escape. Examined through the lenses of quantum mechanics, they can radiate at a definite temperature inverse to their mass and horizon radius. Hawking radiation, whose spectrum was calculated considering particles scattering off black holes, is connected to the paradox of the loss of information falling into them. Information can become non-fungible, due to scrambling. We demonstrate this feature not to be restricted to curved space-times: soft radiation scattering in a flat space-time does scramble information as well. To this end, we compute the scrambling of information through the tripartite mutual information in a scattering process off a black hole and compare it with the flat space-time analog. We show that the scrambling power of the gravitational field of a black hole is negligible with respect to the scrambling power of flat space-time.
Braneshop, and
the US National Science Foundation.
SciRate