Modern Physics Letters B

Many-body Hilbert space is a functional vector space with the natural structure of an algebra, in which vector multiplication is ordinary multiplication of wave functions. This algebra is finite-dimensional, with exactly $N{!}^{d-1}$ generators for N identical particles, bosons or fermions, in d dimensions. The generators are called shapes. Each shape is a possible many-body vacuum. Shapes are natural generalizations of the ground-state Slater determinant to more than one dimension. Physical states, including the ground state, are superpositions of shapes with symmetric-function coefficients, for both bosons and fermions. These symmetric functions may be interpreted as bosonic excitations of the shapes. The algebraic structure of Hilbert space described here provides qualitative insights into long-standing issues of many-body physics, including the fermion sign problem and the microscopic origin of bands in the spectra of finite systems.

A tunable plasmonic induced transparency (PIT)-based light switching is proposed and investigated. The proposed structure consists of a bus waveguide, two nanoresonators and an optofluidic pump system for actively tuning the system’s transmission. By using the finite difference time domain method, it is found that the interferences between the dark and bright mode resonators can be controlled by manipulating the fluid filled in the resonator, leading to an actively tunable plasmonic switch, the transmittance can be flexibly tuned from near unity to zero. The structure in our paper has the following advantages, such as ultracompact size and easy fabrication. Our study will provide a possibility for designing the ultrafast devices in highly integrated optical circuits.

A two-phase solidification model was used that incorporates the descriptions of natural convection, heat transfer, solute transport and solid movement at macroscopic scale with microscopic relations for grain nucleation and growth. The implementation of the two-phase model was validated by comparisons with a consensus of previous numerical simulation for Sn-5wt.%Pb alloy and with experiment for Mg-4wt.%Y alloy cast in one-side-chilled resin sand mould. With free movement of globular grains in the bulk liquid, effects of melt superheat and nucleation density on fluid flow behavior and macrosegregation during solidification of Mg-4wt.%Y alloy were numerically investigated. It was found that a lower melt superheat and a higher nucleation density decrease the severity of macrosegregation by weakening the flotation of grains.

The effect of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) addition on the phase formation and the superconducting properties of GdBa₂Cu₃O${}_{7-\delta }$ phase has been studied. Therefore, composite superconductor samples of type (CNTs)${}_x$ GdBa₂Cu₃O${}_{7-\delta }$, 0.0 $\le x\le$ 0.1 wt.% have been synthesized by a standard solid-state reaction technique. The samples have been characterized using X-ray powder diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results of XRD show an enhancement in the phase formation up to 0.06 wt.% and 0.08 wt.% for SWCNTs and MWCNTs, respectively. SEM and TEM reveal that CNTs form an electrical network resulting in well-connected superconducting grains. The electrical properties of the prepared samples have been examined by electric resistivity and I–V measurements, and their results reinforce the XRD, SEM and TEM. Consequently, both $T_c$ and $J_c$ improve as the addition percentage increases up to 0.06 wt.% and 0.08 wt.% for SWCNTs and MWCNTs, respectively.

First-principles calculations are performed to study the electronic and magnetic properties of monolayer MnS₂. Based on the electronic structure, a half-metallic state is predicted for monolayer MnS₂. The magnetic moment is 3.0 ${\mu }_B$ per formula unit, and the main contribution is localized at the transition metal site Mn with a local moment of 3.733 ${\mu }_B$. The magnetic anisotropy energy (MAE) is 0.056 meV per formula unit with an easy axis perpendicular to the plane, and it indicates that monolayer MnS₂ belongs to the category of Ising magnets. The positive MAE of nanosheets mainly stems from the area around $\mathrm{\Gamma }$ in the reciprocal space. To find the microscopic origin, we take the method of the second-order spin orbit coupling. The occupied spin-up dz² state and the unoccupied spin-down dyz states in the $\mathrm{\Gamma }$ point through the $L_x$ operator make positive contributions to the MAE.

The “blue–green window” in the ocean plays an important role in functions such as communication between vessels, underwater target identification, and remote sensing. In this study, the transmission process of blue–green light in the upper ocean is analyzed numerically using the Monte Carlo method. First, the effect of total number of photons on the numerical results is evaluated, and the most favorable number is chosen to ensure accuracy without excessive costs for calculation. Then, the physical and mathematical models are constructed. The rough sea surface is generated under windy conditions and the transmission signals are measured in the far field. Therefore, it can be conceptualized as a 1D slab with a rough boundary surface. Under windy conditions, these bubbles form layers that are horizontally homogeneous and decay exponentially with depth under the influence of gravity. The effects of bubble populations on the process of blue–green light transmission at different wind speeds, wavelengths, angle of incidence and chlorophyll-$a$ concentrations are studied for both air-incident and water-incident cases. The results of this study indicate that the transmission process of blue–green light is significantly influenced by bubbles under high wind-speed conditions.

In this paper, the effect of magnetic field on the wave propagation in rectangular nanoplates based on two-variable refined plate theory is studied. In order to capture the size effects, the strain gradient theory with one length scale parameter is used. From our knowledge, it is the first time that two-variable refined plate theory is adopted for studying bulk waves in nanoplates. This type of refined plate theory has only two unknowns which reduces the complexity of the governing equations. To show the accuracy of this work, several comparisons are made with available results in open literature.

In this work, highly birefringent large mode area (LMA) photonic crystal fiber (PCF) structure for interferometric sensor applications is proposed. The effective mode area, birefringence and the sensitivity coefficient of the proposed PCF structure by employing the full vectorial finite element method (FV-FEM) have been thoroughly investigated. The numerical results have shown that proposed structure simultaneously offers high birefringence of order 10${}^{-3}$, adequately LMA and high sensitivity for various liquid analytes by employing the elliptical liquid core holes.

The half-vortex stability of the stripe phase in spin-orbit (SO) coupled Bose–Einstein condensate (BEC) is discussed through the multi-mode theory. We find that when the energy of the Rabi coupling is close to zero, the half-vortex in the trap center is always dynamically stable; when the energy becomes larger, the vortex may be structurally unstable. Both of the results are confirmed by the numerical simulation of the full Gross–Pitaevskii equation.

In this research, rod-like undoped and Zn doped h-MoO₃ thin films were grown on top of MoO₃ seed layers, using hydrothermal technique without adding any surfactant. Seed layers of MoO₃ were coated on top of glass substrates using spray pyrolysis technique. Structural, morphological and optical properties of thin films were examined. XRD pattern analysis showed that the seed layer has orthorhombic crystal structure. Also, it confirms the formation of hexagonal structure for thin films grown by hydrothermal. FESEM images show the formation of long, well-shaped hexagonal rod-likes. UV-Vis spectroscopy reveals band gap increasing from 3.2 eV to 3.54 eV, by increasing Zn.