Modern Physics Letters A

In this paper, one of the most important diagrams of weak interaction (vacuum polarization) is studied in Krein space quantization (KSQ). This diagram has divergent terms in Hilbert space which must be eliminated using a traditional regularization method like dimensional regularization whereas in KSQ the result is automatically finite and does not need renormalization.

We propose a new model of D = 4 Gauss–Bonnet gravity. To avoid the usual property of the integral over the standard D = 4 Gauss–Bonnet scalar becoming a total derivative term, we employ the formalism of metric-independent non-Riemannian spacetime volume elements which makes the D = 4 Gauss–Bonnet action term nontrivial without the need to couple it to matter fields unlike the case of ordinary D = 4 Gauss–Bonnet gravity models. The non-Riemannian volume element dynamically triggers the Gauss–Bonnet scalar to be an arbitrary integration constant M on-shell, which in turn has several interesting cosmological implications. (i) It yields specific solutions for the Hubble parameter and the Friedmann scale factor as functions of time, which are completely independent of the matter dynamics, i.e. there is no back reaction by matter on the cosmological metric. (ii) For M$>$0, it predicts a “coasting”-like evolution immediately after the Big Bang, and it yields a late universe with dynamically produced dark energy density given through M. (iii) For the special value M = 0, we obtain exactly a linear “coasting” cosmology. (iv) For M$<$0, we have in addition to the Big Bang also a Big Crunch with “coasting”-like evolution around both. (v) It allows for an explicit analytic solution of the pertinent Friedmann and $\varphi$ scalar field equations of motion, while dynamically fixing uniquely the functional dependence on $\varphi$ of the scalar potential.

In this paper, we consider the DSR-GUP which was first proposed by two of us [W. S. Chung and H. Hassanabadi, Phys. Lett. B 785, 127 (2018)]. Here, we introduce the deformed derivative corresponding to DSR-GUP to discuss the quantum mechanics based on DSR-GUP in an algebraical way. We use the deformed Fourier transform and its inverse transform to discuss the plane wave in $x$-space and Gaussian packet. We also extend our discussion to the (1 + 1)-dimensional case. As examples, we discuss the Ramsauer–Townsend effect and delta potential.

This paper presents the results of the nuclear electrical quadrupole moment of the ¹⁷O and ²H before and after their scattering interaction near the Coulomb barrier. The distribution of nuclei’s charge (the quadrupole moment of nuclei) was examined for ²H and ¹⁷O when interacting together. The interaction potential between the nuclei was achieved using the double-folding model. Also, the wave functions of the interacting nuclei were replaced with the density functions. The wave functions of the interacting nuclei were obtained through the D-dimensional Schrödinger equation with the pseudo-Coulomb potential plus ring-shaped potential and Yukawa potential by the Nikiforov–Uvarov solution method.

Higher-order nonlinear evolution equations are important for describing the wave propagation of second- and higher-order number of fields in optical fiber systems with higher-order effects. One of these equations is the coupled complex modified Korteweg–de Vries (ccmKdV) equation. In this paper, we study noncommutative (nc) generalization of ccmKdV equation. We present Darboux and binary Darboux transformations (DTs) for the nc-ccmKdV equation and then construct its Quasi-Grammian solutions. Further, single and double-hump soliton solutions of first- and second-order are given in commutative settings.

Among various dark energy models, Tsallis holographic dark energy model shows the dynamical enthusiasm to describe the transition phase of the universe. In this paper, we consider Tsallis holographic dark energy with event and apparent horizon as an infrared cutoff in the framework of dynamical Chern–Simon modified gravity and non-flat FRW universe. We explore Hubble, equation of state and deceleration parameters and found that Hubble parameter lies in the range $80_{-60}^{+60}$ and $120_{-40}^{+40}$ for event and apparent horizon trajectories, respectively. It is mentioned here that the equation of state parameter lies within the range $-1.3\mp 0.4$ (event) and $-1.125\mp 0.125$ (apparent). Also, deceleration parameter for both cases show accelerated and decelerated phase of universe as well as cosmological constant. Moreover, we also checked the stability of our model through square speed of sound, which shows the positive behavior (exhibits the stability of the model). Finally, we observe that the generalized second law of thermodynamics remains valid in both cases of horizon.

We analyze the one-loop correction to $Z\to \nu \nu$ decay in framework of Minimal R-symmetric Supersymmetric Standard Model (MRSSM) in detail with normal and inverse neutrino mass orderings, as a function of $\mathrm{\text{tan}}\beta$, Dirac mass parameters $M_D^W$ and ${\mu }_u({\mu }_d)$, slepton mass $m_l$ that parametrize the mass matrices. The numerical results indicate that the branching ratio for $Z\to \nu \nu$ decay is compatible with the experimental measurement and the SM expectation at $2\sigma$ level. For inverse neutrino mass ordering, the prediction exceeds the SM expectation at $1\sigma$ level. The prediction on $\mathrm{\text{Br}}(Z\to \nu \nu )$ increases proportionally to $\mathrm{\text{tan}}\beta$ and inversely proportionally to $m_l$. For normal neutrino mass ordering, the peak value of the prediction on $\mathrm{\text{Br}}(Z\to \nu \nu )$ exceeds the SM expectation at $1\sigma$ level.

We consider a vacuum static spacetime in a finite size cavity. On the boundary, we specify a metric and a finite constant local temperature $T$. No spherical or any other spatial symmetry is assumed. We show that (i) inside a cavity, only a black hole or flat spacetime are possible, whereas a curved horizonless regular spacetime is excluded, (ii) in the limit when the horizon area shrinks, the Hawking temperature diverges, (iii) for the existence of a black hole, $T$ should be high enough. When $T\to \infty$, a black hole phase is favorable thermodynamically. Our consideration essentially uses the coordinate system introduced by Israel in his famous proof of the uniqueness theorem.

Heavy neutrino–antineutrino oscillations can appear in mechanisms of low-scale neutrino mass generation, where pairs of heavy neutrinos have almost degenerate masses. We discuss the case where the heavy neutrinos are sufficiently long-lived to decay displaced from the primary vertex, such that the oscillations of the heavy neutrinos into antineutrinos can potentially be observed at the (high-luminosity) LHC and at currently planned future collider experiments. The observation of these oscillations would allow to measure the mass splitting of the respective heavy neutrino pair, providing a deep insight into the nature of the neutrino mass generation mechanism.

A new approach to the classical limit of Grover’s algorithm is discussed by assuming a very rapid dephasing of a system between consecutive Grover’s unitary operations, which drives pure quantum states to decohered mixed states. One can identify a specific element among $N$ unsorted elements by a probability of the order of unity after $k\sim N$ steps of classical amplification, which is realized by a combination of Grover’s unitary operation and rapid dephasing, in contrast to $k\sim \pi \sqrt{N}/4$ steps in quantum mechanical amplification. The initial two-state system with enormously unbalanced existence probabilities, which is realized by a chosen specific state and a superposition of all the rest of the states among $N$ unsorted states, is crucial in the present analysis of classical amplification. This analysis illustrates Grover’s algorithm in extremely noisy circumstances. A similar increase from $k\sim \sqrt{N}$ to $k\sim N$ steps due to the loss of quantum coherence takes place in the analog model of Farhi and Gutmann where the entanglement does not play an obvious role. This supports a view that entanglement is crucial in quantum computation to describe quantum states by a set of qubits, but the actual speedup of the quantum computation is based on quantum coherence.