Modern Physics Letters A

In this paper, we review recent progress on relativistic hydrodynamics in (2 + 1) dimensions with an external magnetic field. We discuss the formalism allowing for momentum loss due to the explicit and spontaneous breaking of translation invariance by scalar operators. We also compare to some results from the gauge/gravity correspondence.

In this paper, we adapted the Appleby–Battye–Starobinsky model of $F(R)$ gravity towards describing double cosmological inflation and formation of primordial black holes with masses up to $10^{19}$ g in the single-field model. We found that it is possible to get an enhancement of the power spectrum of scalar curvature perturbations to the level beyond the Hawking (black hole evaporation) limit of $10^{15}$ g, so that the primordial black holes resulting from gravitational collapse of those large primordial perturbations can survive in the present universe and form part of cold dark matter. Our results agree with the current measurements of cosmic microwave background radiation within $3\sigma$ but require fine-tuning of the parameters.

Following our previous work [C. Y. Liu, Mod. Phys. Lett. A 36, 2150080 (2021), doi:10.1142/S0217732321500802], we investigate the masses of some pseudoscalar mesons which have the anomalous decays from axial anomaly (the Adler–Bell–Jackiw anomaly). We apply a non-perturbative mass formula to study the neutral single flavor pseudoscalar meson $(f\bar{f})$. We find the mass of pseudoscalar meson $(c\bar{c})(m_{(c\bar{c})}\approx 7.6\mathrm{\text{GeV}})$ which can solve the problem of double $c\bar{c}$ production in $e^{+}{e}^{-}$ annihilation at $\sqrt{s}\approx 10.6\mathrm{\text{GeV}}$ and obtain the mass of pseudoscalar meson $(b\bar{b})(m_{(b\bar{b})}\approx 28.4\mathrm{\text{GeV}})$ which is the same as the invariant mass of ${\mu }^{+}{\mu }^{-}$ pairs produced in association with $b$ jet in $pp$-collisions at the LHC. We generalize this formula to three flavors pseudoscalar mesons, we obtain the mass of ${\eta }^{\prime }$ meson $(m_{{\eta }^{\prime }}\approx 961\mathrm{\text{MeV}})$ which is almost the same as the experimental value $(m_{{\eta }^{\prime }}^{\mathrm{\text{exp}}}\approx 958\mathrm{\text{MeV}})$.

Non-perturbative effects of the QED-vacuum reconstruction exposed to the supercritical Coulomb field are considered with emphasis on the behavior of the vacuum energy ${{ℰ}}_{\mathrm{\text{V P}}}$. It is shown that in the supercritical region ${{ℰ}}_{\mathrm{\text{V P}}}$ turns out to be a decreasing function of the Coulomb source, resulting in decay into the negative range as $\sim -Z^4/R$, and that it is indeed the decline of ${{ℰ}}_{\mathrm{\text{V P}}}$, which provides the required energy for (presumably possible) positron emission. The properties of the resonance decay, found this way, are in agreement with those achieved by other methods. The additional problems of spontaneous emission, caused by lepton number conservation, are also discussed.

It is widely accepted that a huge and intense magnetic field is created along with the exotic state of matter in heavy-ion collision. The photon yield from quark-gluon plasma created in a magnetic environment is studied using a thermal quasi-particle mass. The quarks acquire this mass depending on the temperature and nonzero value of quark chemical potential which gets modified as magnetized effective quark mass (MEQM) in the presence of magnetic field. The total photon rate is shown for one loop process incorporating MEQM. It is found that the emission rate to lowest order increases strongly with increasing of the quark chemical potential and temperature. The enhanced yield in photon is also compared with the recently reported theoretical results.

With the post-Newtonian approximation, the energy of Schwarzschild spacetime in the Weinberg prescription is obtained. The energy for the first post-Newtonian approximation $E^{(1)}=m$ gives the Newtonian treatment of Schwarzschild spacetime. However, for the second post-Newtonian approximation, the energy is shown that $E^{(1)}$ adds extra terms $E^{(2)}$ which consist of the energy stored in the configuration $E_{\mathrm{\text{config}}}$, in the gravitational field $E_{\mathrm{\text{field}}}$, and a term of surface integral. These extra terms give post-Newtonian corrections to the Newtonian treatment.

A four-dimensional solution of the classical equation of motion in the low-energy effective field theory for heterotic string theory is chosen. Popularly, this is known as Kerr–Sen black hole. Thermodynamic picture for this particular black hole is constructed. Applying the generalized uncertainty principle (GUP), the first-order correction of it in connection with the thermal heat capacity (THC) and due to conformal field theory (CFT) background are studied. All the cases are pointing towards an unstable thermodynamic phase of the concerned black holes. Phase transitions are located by studying where signs of the heat capacity are changing. Unlike the black holes embedded in AdS space, first-order corrected entropy is found to be unphysical. Photons by tunneling rate are calculated. A comparative study of the effect of generalized uncertainty principle parameter $\alpha$ along with the black holes’ parameters on the thermodynamics of the black hole is presented.

According to standard cosmology, the universe is homogeneous and isotropic at large scales. However, some anisotropies can be observed at the local scale in the universe through various ways. Here, we have studied the Bianchi Type I model by customizing the scale factors to understand the anisotropic nature of the universe. We have considered two cases with slight modifications of scale factors in different directions in the generalized Bianchi Type I metric equation, and compared the results with the $\mathrm{\Lambda }$CDM model and also with available cosmological observational data. Through this study, we also want to predict the possible degree of anisotropy present in the early universe and its evolution to current time by calculating the value of density parameter for anisotropy $({\mathrm{\Omega }}_{\sigma })$ for both low and high redshift $(z)$ along with the possible relative anisotropy that exist among different directions. It is found that there was a relatively higher amount of anisotropy in the early universe and the anisotropic nature of the universe vanishes at the near past and the present epochs. Thus, at near past and present stages of the universe there is no effective distinction between this anisotropic model and the standard $\mathrm{\Lambda }$CDM model.

In this paper, we have analyzed the ground state structural properties of fermium-isotopes in the mass range $221\le A\le 279$ within the relativistic mean-field with NL3${}^{\ast }$ and Relativistic Hartree–Bogoliubov approach with DD-ME2 parameter sets. The bulk properties, such as binding energy, root mean-square charge radius, quadruple deformation parameter, chemical potentials, two-neutron separation energy and differential two- neutron separation energy, are estimated for the above Fm- isotopic chain. All the calculated observables are compared with finite range droplet model (FRDM) predictions and experimental data wherever available. The analysis predicts the existence of shell closure in the neutron-rich region of the isotopic chain at $A=225$. The decay properties such as the $\alpha$-decay energy and corresponding half-life for three decay chains i.e. ${}^{243}$Fm, ${}^{245}$Fm and ${}^{247}$Fm are studied. Six different empirical formulae, namely; Viola-Seaborg, Royer, modified B. Alex Brown, Parkhomenko–Sobiczewski, Universal decay law and modified universal decay law are employed to ascertain the numerical dependency of the half-life for each decay energy. A comparative study of $Q$-values and half-lives for these decay chains gives a good signature of the calculated results. The half-life calculations of three decay chains suggest that ${}^{231}$Pu, ${}^{233}$Pu, ${}^{235}$Pu are shell closure nuclei having maximum half-lives, whereas ${}^{243}$Fm, ${}^{245}$Fm and ${}^{247}$Fm are shell stabilized with lower half-lives.