Table of contents

Bertotti-Robinson spacetimes are topologically $AdS_2 \times S^2$ and described by a conformally flat metric. Together with the Coulomb electric potential, they provide a class of static, geodetically complete Einstein-Maxwell solutions. We show here that the Bertotti-Robinson metric together with Wu-Yang magnetic pole potentials give a class of static solutions of a system of non-minimally coupled Einstein-Yang-Mills equations that may be relevant for investigating vacuum polarization effects in a first-order perturbative approach to quantum fields.

Taking the generalized uncertainty principle into account, we apply the corrected state density and brick-wall method to calculate the entropy of a novel four-dimensional Gauss-Bonnet black hole surrounded by an arbitrary field with spin $s\leq2$. It is shown that the leading and logarithmic terms of the entropy are respectively modified by the quantum gravity effect and spin of the field. Meanwhile, the correction coming from gravitational interaction has the same form as the leading term, that is, they all are proportional to the horizon area and inversely proportional to the gravity correction factor. The ratio of the correction term to the leading one is respectively −5/7 and −1395/1764 for Bose and Fermi cases, where negative sign means that the effect of quantum gravity decreases the entropy. It is very interesting that these proportion values are independent of the black hole characteristics.

We consider a one-dimensional stationary stochastic process $x(\tau)$ of duration T. We study the probability density function (PDF) $P(t_{\rm m}|T)$ of the time $t_{\rm m}$ at which $x(\tau)$ reaches its global maximum. By using a path integral method, we compute $P(t_{\rm m}|T)$ for a number of equilibrium and nonequilibrium stationary processes, including the Ornstein-Uhlenbeck process, Brownian motion with stochastic resetting and a single confined run-and-tumble particle. For a large class of equilibrium stationary processes that correspond to diffusion in a confining potential, we show that the scaled distribution $P(t_{\rm m}|T)$, for large T, has a universal form (independent of the details of the potential). This universal distribution is uniform in the "bulk", i.e., for $0 \ll t_{\rm m} \ll T$ and has a nontrivial edge scaling behavior for $t_{\rm m} \to 0$ (and when $t_{\rm m} \to T$), that we compute exactly. Moreover, we show that for any equilibrium process the PDF $P(t_{\rm m}|T)$ is symmetric around $t_{\rm m}=T/2$, i.e., $P(t_{\rm m}|T)=P(T-t_{\rm m}|T)$. This symmetry provides a simple method to decide whether a given stationary time series $x(\tau)$ is at equilibrium or not.

We study the relaxation dynamics of quantum turbulence in a two-component Bose-Einstein condensate containing half-quantum vortices. We find a temporal scaling regime for the number of vortices and the correlation lengths that at early times is strongly dependent on the relative strength of the inter-species interaction. At later times we find that the scaling becomes universal, independent of the inter-species interaction, and approaches that numerically observed in a scalar Bose-Einstein condensate.

We report the role of local bentonite clay in the removal of Cu²⁺ ions from aqueous solution. The fine bentonite clay powder was analysed by XRD, FTIR, SEM and DLS analysis techniques. Further, the adsorption experiments were carried out by varying many factors such as weight and size of bentonite clay, residence time, pH of the solution, stirring rate, temperature, and flow rate. The optimum conditions for effective removal of Cu²⁺ ions was 1 g dose of bentonite and 63 μm size of bentonite, 50 minutes of residence time and 50 °C temperature at pH 3 with a flow rate of 1 L/min. The data fitted well the Freundlich model and a maximum adsorption capacity of 61.72 mg/g has been obtained. The value of Gibbs free energy changes (${\Delta}G^{\circ}$), enthalpy changes (${\Delta}H^{\circ}$) and entropy changes (${\Delta}$S°) were found to be $-3819.86\ \text{J~mol}^{-1}\text{K}^{-1}$, $+15079.10\ \text{J mol}^{-1}\text{K}^{-1}$ and $+58.60\ \text{J mol}^{-1}\text{K}^{-1}$, respectively.

In this work, based on the generalized Dunkl derivative in quantum mechanics we study the one-dimensional Schrödinger equation with a harmonic oscillator potential and obtain the energy eigenvalues. The principal thermodynamical properties including the Helmholtz free energy, mean energy and entropy are carried out. The effects of the Dunkl parameters on the thermodynamical quantities for even parity are discussed. The case of the odd parity can be easily obtained by substitution of the $b\rightarrow -b$ and $\gamma\rightarrow -\gamma$. All results in the limit case are reduced to ordinary statistical mechanics.

In the last two decades, a large number of exotic hadron states have been observed in experiments, which arouses great attention in the hadron physics community. In this short review, we briefly summarize progresses of our group on several exotic hadron states. Two approaches, quenched and unquenched quark models, are adopted in the calculation. The channel coupling effects, the multiquark states couple to open channels and the quark-antiquark states couple to meson-meson states, are emphasized. X(3872) is showed to be a mixture state of $c\bar{c}$ and $D\bar{D}^*$ in the unquenched quark model. X(2900) can be explained as a resonance state $\bar{D}^{*}K^{*}$ with the quantum numbers $IJ^{P}=00^{+}$ in both the quark delocalization color screening model and the chiral quark model. The reported state X(6900) can be explained as a compact resonance state with $IJ^{P}=00^{+}$ in both two quark models, and several fully heavy tetraquark states are predicated. The possible hidden-charm pentaquarks are systematically investigated in QDCSM, and seven resonance states are obtained in the corresponding baryon-meson scattering process, among which the $\Sigma_{c}D$ with $J^{P}=\frac{1}{2}^{-}$, $\Sigma_{c}D^{*}$ with $J^{P}=\frac{3}{2}^{-}$ and $J^{P}=\frac{1}{2}^{-}$ are consistent with the experimental report of P_c(4312), P_c(4440), and P_c(4457), respectively. More experimental data on exotic hadron states are vital for understanding exotic hadron states in quark models.

Some time ago, the infrared limit of the Abelian Chern-Simons-Proca theory was investigated. In this letter, we show how the Chern-Simons-Proca theory can emerge as an effective low-energy theory. Our result is obtained by means of a procedure that takes into account the proliferation, or dilution, of topological defects present in the system.

We study quantum gravity corrections to the thermodynamic quantities of Reissner-Nordström anti-de Sitter black hole surrounded by quintessence by evaluating the Hawking radiation of zitterbewegung particles under the Generalized Uncertainty Principle (GUP) effect. By using the modified Hawking temperature of the black hole, we derive the thermodynamic equation of state and the Helmholtz free energy. We discuss global stability conditions and phase transitions by plotting the $P-V$ and $P-T$ planes. We also assume that the black hole is a heat engine where the Carnot cycle is performed. We observe that the efficiency under the GUP effect is higher than the standard one when attractive Coulomb interaction is considered with the influence of zitterbewegung particles.

In the present work, we investigate the general properties of low-lying experimental bands in three $N = 89$ isotones, ¹⁵⁵Dy $(Z = 66)$, ¹⁵⁶Ho $(Z = 67)$, ¹⁵⁷Er $(Z = 68)$, at high spin within the cranked Nilsson-Strutinsky formalism. The excitation energies of the yrast bands have been compared with the experimental findings, and good agreements are observed. Our calculations show that with increasing total nuclear spin, the collectivity decreases gradually leading to the termination. In addition, nuclei with 10–12 particles outside the closed core terminate within configurations with no hole in the core.

In this work, we study the impact of temporally varying gravity on an idealized shallow conducting fluid with a free surface. We formulate the problem in terms of the shallow magnetohydrodynamic (SMHD) equations which allows the study of the resulting anisotropy in the context of a Faraday instability. We simplify the linear stability problem into a Mathieu equation by assuming gravity is periodic in time. Using the existing theory of Mathieu's equation, we find that anisotropy occurs, with wave vectors parallel to the imposed magnetic field stabilized. We describe the regions of instability in wave number space.

We consider the quantum electrodynamic corrections to the two-stream instability. We find these corrections vanish at first order unless a guiding magnetic field $\mathbf{B}_0$ is considered. With respect to the classical version of the instability, quantum electrodynamic effects reduce the most unstable wave vector and its growth rate by a factor $\sqrt{1+\xi}$, with $\xi = \frac{\alpha}{9\pi} (B_0/B_{cr})^2$, where α is the fine-structure constant and B_cr the Schwinger critical magnetic field. Although derived for a cold system, these results are valid for the kinetic case. The results are valid in the range $\xi \ll 1$ and, actually, up to linear corrections in ξ.

Amorphous and crystalline solids have long been considered as two distinct kinds of rigidity at the opposite ends of the order-disorder continuum. Crystals are usually treated in equilibrium with defects arising as perturbations or excitations (Ashcroft N. W. and Mermin N. D., Solid State Physics (Thomson Brooks/Cole) 1976). Amorphous solids are frustrated and out of equilibrium where preparation protocol can be important. Nevertheless the onset of rigidity of athermal amorphous matter (Liu A. J. and Nagel S. R., Nature, 396 (1998) 21) has been established as a critical point with extended universality. The universal scaling behavior that characterizes jamming at high amorphisation has been demonstrated by a wealth of simulations and models, including an infinite-dimensional mean field theory (Charbonneau P. et al., Annu. Rev. Condens. Matter Phys., 8 (2017) 265). At the other end, the crystal of minimal disorder has not been shown to display such universal behavior. Here we provide numerical evidence that slightly polydisperse crystals can become critically jammed at packing fractions extremely close to the maximum close-packed density. At the near-crystal jamming point some of the characteristic scalings are universal and agree with maximally amorphous jamming, others are novel. The set of scaling results we provide establishes jamming criticality of maximum-packing crystals in 2 and 3 dimensions.

We present the growth dynamics of breath figures on phase change materials using numerical simulations. We propose a numerical model which accounts for both growth due to condensation and random motion of droplets on the substrate. We call this model as growth and random motion (GRM) model. Our analysis shows that for dynamics of droplet growth without droplet motion, simulation results are in good agreement with well-established theories of growth laws and self-similarity in surface coverage. We report the emergence of a growth law in the coalescence-dominated regime for the droplets growing simultaneously by condensation and droplet motion. The overall growth of breath figures (BF) exhibits four growth regions, namely, initial $\langle R \rangle \sim t^{\alpha_1 }$, intermediate or crossover $\langle R \rangle \sim t^{\alpha_2 }$, coalescence-dominated regime $\langle R \rangle \sim t^{\alpha_3 }$, and no coalescence regime in late time $\langle R \rangle \sim t^{\alpha_4 }$, where $\langle R \rangle$ and t are the average droplet radius and time, respectively. The power law exponents are $\alpha_1 \approx 1/2$, $\alpha_2 \approx 1.0$, $\alpha_3 \approx 3.0$, and $\alpha_4 \approx 1/3$. Moreover, the surface coverage reaches a maximum value $\varepsilon^2 \approx 0.35$ where the third growth regime $t^{\alpha_3 }$ starts. We also demonstrate that during the growth dynamics of BF, the random motion amplitude δ and its probability p(R) linked to the power exponent γ of droplet radius R have a specific limiting range within which its effect is more predominant.

Grains are widely assumed to be characterized by a single temperature —derived either from the configurational entropy, or employing the kinetic theory. Yet granular media do have two temperatures, T_g and T, pertaining to the grains and atoms. It is argued here that a two-temperature plasma yields a more useful analogy for grains than a molecular gas: 1) Irreversible collisions also occur in plasma, to reach the equilibrium of equal temperature. 2) The plasma energy is not linear in the two temperatures; it is quadratic in the temperature difference, minimal at equilibrium. Both points have valid analogues in grains, yielding useful insights.

In solids, electronic Bloch states are formed by atomic orbitals. While it is natural to expect that orbital composition and information about Bloch states can be manipulated and transported, in analogy to the spin degree of freedom extensively studied in past decades, it has been assumed that orbital quenching by the crystal field prevents significant dynamics of orbital degrees of freedom. However, recent studies reveal that an orbital current, given by the flow of electrons with a finite orbital angular momentum, can be electrically generated and transported in wide classes of materials despite the effect of orbital quenching in the ground state. Orbital currents also play a fundamental role in the mechanisms of other transport phenomena such as spin Hall effect and valley Hall effect. Most importantly, it has been proposed that orbital currents can be used to induce magnetization dynamics, which is one of the most pivotal and explored aspects of magnetism. Here, we give an overview of recent progress and the current status of research on orbital currents. We review proposed physical mechanisms for generating orbital currents and discuss candidate materials where orbital currents are manifest. We review recent experiments on orbital current generation and transport and discuss various experimental methods to quantify this elusive object at the heart of orbitronics —an area which exploits the orbital degree of freedom as an information carrier in solid-state devices.

We experimentally investigate transport properties of a hybrid structure, which consists of a thin single crystal SnSe flake on a top of 5 μm spaced Au leads. The structure initially is in highly conductive state, while it can be switched to the low-conductive one at high currents due to the Joule heating of the sample, which should be identified as phase transition to the symmetric β-Cmcm phase in SnSe. For the highly conductive state, there is significant hysteresis in $\textrm{d}I/\textrm{d}V(V)$ curves at low biases, so the sample conductance depends on the sign of the applied bias change. This hysteretic behavior reflects slow relaxation due to additional polarization current in the ferroelectric SnSe phase, which we confirm by direct measurement of time-dependent relaxation curves. In contrast, we observe no noticeable relaxation or low-bias hysteresis for the quenched low-conductive phase. Thus, the ferroelectric behavior can be switched on or off in transport through hybrid SnSe structure by controllable phase transition to the symmetric β-Cmcm phase. This result can also be important for nonvolatile memory development, e.g., phase change memory for neuromorphic computations or other applications in artificial intelligence and modern electronics.

The Fukui-Todo algorithm is an important element of the array of simulational approaches to tackling critical phenomena in statistical physics. The partition-function-zero approach is of fundamental importance to understand such phenomena and a precise tool to measure their properties. However, because the Fukui-Todo algorithm bypasses sample-by-sample energy computation, zeros cannot easily be harnessed through the energy distribution. Here this obstacle is overcome by a novel reweighting technique and zero-detection protocol. The efficacy of the approach is demonstrated in simple iconic models which feature transitions of both first and second order.