International Journal of Modern Physics D

The relation between celestial holography and Liouville field theory is investigated. It is shown that the duality relations between different Selberg-type integrals appearing in the Coulomb gas realization of Liouville correlation functions induce a series of relations between celestial amplitudes with shifted values of the operator dimensions $\mathrm{\Delta }$.

In this paper, we investigate the primordial power spectrum of cosmological tensor perturbations in the dressed metric approach to Loop Quantum Cosmology. We compute the background-dependent effective mass that affects their propagation using the effective description of Loop Quantum Cosmology and show that this mass can be approximated in different cosmological epochs by appropriate analytic functions. Moreover, in each of those epochs we can analytically solve the propagation of the perturbations, then obtaining the general solution globally by continuity requirements. On the other hand, since there are regimes far away from slow roll in the considered background evolution, the Bunch–Davies state does not provide a privileged choice of vacuum that would pick out a specific solution for the perturbations. Instead, we select the state of these perturbations by a recently proposed criterion that removes unwanted oscillations in the power spectrum. We compute the spectrum of this vacuum and compare it with other spectra obtained in the literature, especially with one corresponding to the hybrid approach to Loop Quantum Cosmology. Finally, we notice that the same type of background dynamics is found in a phenomenological approach to quantum gravity based on thermodynamics, allowing in this case a free value for the tantamount of the critical density. Extending the dressed metric proposal to this phenomenological model, one might expect a similar form for the associated primordial power spectrum.

This work deals with the spherical collapse of matter overdensity for two reconstructed dark energy models. One of the models is reconstructed from parametrization of effective or total equation of state of energy components in the universe ($w_{\mathrm{\text{eff}}}$ model) and the other model is the constant dark energy equation of state model, namely the wCDM model. The linear evolution and nonlinear evolution of matter density contrast are studied for the present models. It is observed that the linear and even the nonlinear evolutions of density contract are almost indistinguishable in these two models. The critical density contrast at collapse as a function of redshift is also studied. The nature of critical density contrast is also found to be degenerate in the present models. Further, the number count of collapsed objects or dark matter halos along redshift is also studied. Two different halo mass functions, namely the Press–Schechter mass function and the Sheth–Tormen mass function, are adopted in this context. It is observed that for both the mass functions, the $w_{\mathrm{\text{eff}}}$ model has slightly higher number of halos at very low redshift ($z<0.5$) and at higher redshift the wCDM model has higher number of dark matter halos. On the other hand, it is observed that the Press–Schechter mass function produces slightly higher number of dark matter halos at low redshift compared to Sheth–Tormen mass function and the number of halos is higher for Sheth–Tormen mass function at redshift $z>0.9$ for both the dark energy models. The results clearly show that these two highly degenerate dark energy models are distinguishable in the study of spherical collapse and galaxy cluster number counts.

(i) Investigations of stellar systems known as wide binaries suggest that Newton’s law of gravitation breaks down at low accelerations. This can be explained by proposing a fifth force with $U(1)$ gauge symmetry, whose corresponding gauge boson is the sought for dark matter candidate. (ii) Relativistic causality (i.e. no faster than light signalling) permits nonlocal correlations stronger than those permitted by quantum mechanics. Can this be explained if our universe possesses a second 4D spacetime with a signature opposite to ours? (iii) Such a fifth force, and a second spacetime, arise naturally in a recently proposed theory of unification based on an $E_8\times E_8$ symmetry. Our spacetime arises from breaking of an $SU{(2)}_R\times U{(1)}_{Y\mathrm{\text{DEM}}}$ symmetry, and the second spacetime arises from broken electroweak symmetry.

In this paper, we study the relativistic and nonrelativistic Landau levels for Dirac fermions in the cosmic string spacetime in the context of rainbow gravity in $(3+1)$-dimensions, where we work with the curved Dirac equation with minimal coupling in cylindrical coordinates. Using the tetrads formalism of General Relativity, we obtain a second-order differential equation. Solving this differential equation, we obtain a generalized Laguerre equation as well as the relativistic Landau levels for the fermion and antifermion, where such energy levels are quantized in terms of the quantum numbers n, $m_j$ and $m_s$, and explicitly depends on the rainbow functions $f(\epsilon )$ and $g(\epsilon )$, charge parameter $\sigma$, cyclotron frequency ${\omega }_c$, curvature parameter $\alpha$, and on the square rest energy $m_0^2$ and square z-momentum $k_z^2$, respectively. Posteriorly, we study the nonrelativistic limit of the system, where we obtain the nonrelativistic Landau levels. In both cases (relativistic and nonrelativistic), we graphically analyze the behavior of Landau levels for the three-rainbow gravity scenarios as a function of the magnetic field B and of the curvature parameter $\alpha$. In addition, we also compared our problem with other works, where we verified that our results generalize several particular cases in the literature.

Magnetic fields can be generated in cosmic string wakes due to the Biermann mechanism in the presence of neutrino inhomogeneities. As the cosmic string moves through the plasma, the small magnetic field is amplified by the turbulence in the plasma. Relativistic charged particles which cross the magnetized wake of a cosmic string will therefore emit synchrotron radiation. The opening angle of the cosmic string is very small and so the wake appears like a thin sheet. Assuming a homogeneous magnetic field in the wake of the string, we obtain the synchrotron emission from nonthermal relativistic electrons in the wake of the string. The emitted radiation has a broad peak and is over a wide range of frequency. We show that the spectrum can be mapped to some of the unknown sources in different ranges of the current available catalogues.

In space-based gravitational wave detection, charge management is used to reduce unwanted electrostatic noise by controlling the absolute charge of the test mass (TM). However, the charge management process will cause periodic interruptions in the scientific measurements. In order to minimize the frequency and influence of the interruptions, this paper proposes a method to optimize the electrostatic noise by adding a common voltage to all the actuation electrodes, to precisely adjust the potential difference between the TM and the electrodes. Theoretical analyses and simulation evaluations indicate that the permissible limit of accumulated charge on the TM can be extended from $10^7$ e to $10^8$ e, while maintaining the same electrostatic noise requirement level of $4\times 10^{-16}$ m/s²/Hz${}^{1/2}$. This approach shows that it allows a tenfold extension of the charge management period, significantly reducing interruptions in gravitational wave detection.

In this research, we delve into the localization patterns of fermionic fields within a braneworld setting, employing a modified gravity model denoted as $f(Q)$. Our investigation revolves around two specific models, $f_1(Q)=Q+k{Q}^n$ and $f_2(Q)=Q+k_1{Q}^2+k_2{Q}^3$, where we systematically vary the parameters n and $k_{1,2}$. Through an in-depth analysis encompassing the effective potential, massless, and massive modes, we elucidate how deviations from the conventional Symmetric Teleparallel Equivalent of General Relativity (STEGR) gravity impact the localization of fermionic fields. To ensure greater precision, our methodology integrates probabilistic measures such as Shannon entropy and relative probability. Moreover, we gauge the stability of these models employing Differential Configurational Entropy (DCE), revealing a compelling correlation between the most stable configurations and the emergence of novel structures within the background scalar field. This work significantly contributes to our understanding of the gravitational modifications’ intricate influence on fermionic field localization within braneworld scenarios. By shedding light on these dynamics, it advances the broader comprehension of the interplay between gravity modifications and fermionic field behaviors in these theoretical frameworks.

In this paper, the vacuum energy density and generation of topological mass are investigated for a system of a real and complex scalar fields interacting with each other. In addition to that, it is also included the quartic self-interaction for each one of the fields. The condition imposed on the real field is the periodic condition, while the complex field obey a quasi-periodic condition. The system is placed in a scenario where the CPT-even aether-type Lorentz symmetry violation takes place. We allow that the Lorentz violation affects the fields with different intensities. The vacuum energy density, its loop correction, and the topological mass are evaluated analytically. It is also discussed the possibility of different vacuum states and their corresponding stability requirements, which depends on the conditions imposed on the fields, the interaction coupling constants and also the Lorentz violation parameters. The formalism used here to perform this investigation is the effective potential one, which is written as a loop expansion via path integral in quantum field theory.