Spin Fluid Research Articles

Gravitational Collapse of a Fluid with Torsion into a Universe in a Black Hole

We consider gravitational collapse of a spherically symmetric sphere of a fluid with spin and torsion into a black hole. We use the Tolman metric and the Einstein–Cartan field equations with a relativistic spin fluid as a source. We show that gravitational repulsion of torsion prevents a singularity and replaces it with a nonsingular bounce. Quantum particle production during contraction helps torsion to dominate over shear. Particle production during expansion can generate a finite period of inflation and produce enormous amounts of matter. The resulting closed universe on the other side of the event horizon may have several bounces. Such a universe is oscillatory, with each cycle larger in size then the previous cycle, until it reaches the cosmological size and expands indefinitely. Our universe might have therefore originated from a black hole.

A nonsingular, anisotropic universe in a black hole with torsion and particle production

We consider a universe formed in a black hole in general relativity with spin and torsion. The interior of a Schwarzschild black hole can be represented by the Kantowski–Sachs metric that describes a closed anisotropic universe. We use this metric to derive the Einstein–Cartan field equations with a relativistic spin fluid as a source. We show that torsion may prevent a singularity and replace it with a nonsingular bounce if particle production dominates over shear. Particle production after the last bounce can generate a finite period of inflation, during which the universe expands and isotropizes to the current state. This scenario is only approximate: the Kantowski–Sachs metric is never reached and should be replaced with a more general metric that tends to that of a 3-sphere.

Phase Behavior of Lyotropic Liquid-Crystalline Polymers under Varying Solvent Conditions: Effect of External Fields on the Phase Diagram.

In this work, we report a Density Functional Theory based study of phase behavior of lyotropic liquid-crystalline polymers under both good and varying solvent conditions in the presence of external electric or magnetic field. Our microscopic model for the good solvent case is based on the tangent hard-sphere chain with bond-bending potential to account for the chain stiffness; the variable solvent quality is modeled by adding attractive monomer-monomer interactions. The phase diagrams are constructed in three intensive variables (temperature, pressure, and field strength), and are characterized by the presence of critical and triple lines, which originate from the critical and triple points of the corresponding zero-field case. The merging of critical and triple lines results in the appearance of the "double critical" and "critical triple" points, already known from the earlier studies of the phase behavior of spin fluids in magnetic fields. The important difference of the present model from the spin fluids is due to the finite stiffness of the polymer chains (characterized by their persistence length), which adds an additional parameter controlling the morphology of the phase diagrams.

ГРАВИТАЦИОННЫЙ КОЛЛАПС ЖИДКОГО ОБЪЕКТА С КРУЧЕНИЕМ С ОБРАЗОВАНИЕМ ВСЕЛЕННОЙ В ЧЕРНОЙ ДЫРЕ

We consider gravitational collapse of a spherically symmetric sphere of a fluid with spin and torsion into a black hole. We use the Tolman metric and the Einstein--Cartan field equations with a relativistic spin fluid as a source. We show that gravitational repulsion of torsion prevents a singularity and replaces it with a nonsingular bounce. Quantum particle production during contraction helps torsion to dominate over shear. Particle production during expansion can generate a finite period of inflation and produce enormous amounts of matter. The resulting closed universe on the other side of the event horizon may have several bounces. Such a universe is oscillatory, with each cycle larger in size then the previous cycle, until it reaches the cosmological size and expands indefinitely. Our universe might have therefore originated from a black hole.

Multifunctional modification of viscose fiber using plant extracts formulations

Some plant extracts with specific functions have been used to integrate with textiles, which can not only endowing the fabric with certain functions, but also accord with the concept of environmental protection and sustainable development. In this paper, codonopsis powder and thyme essential oils microcapsule were added to viscose spinning fluid. The obtained viscose fiber with various functions, such as antibacterial activity, anti-mould activity and anti-mites activity. In addition, the durability are also more than 20 washes. The multifunctional viscose fiber has a more extensive application prospect.

Multipartite quantum discord and quantum coherence in Heisenberg–Ising bond alternating chain

The behaviour of multipartite quantum discord and quantum coherence in Heisenberg–Ising bond alternating spin-1 / 2 chain are computed by exploiting the method of quantum renormalisation group (QRG). At larger number of iterations, both quantum coherence and quantum discord have found to exhibit quantum phase transition (QPT) between the spin fluid phase and the Neel phase. In addition, at the critical point, the first derivative of both quantum coherence and quantum discord have shown a non-analytical behaviour. Finally, the scaling behaviour of both quantum coherence and quantum discord has been investigated.

Ferromagnetism-induced phase separation in a two-dimensional spin fluid.

We study the liquid-gas phase separation observed in a system of repulsive particles dressed with ferromagnetically aligning spins, a so-called "spin fluid." Microcanonical ensemble numerical simulations of finite-size systems reveal that magnetization sets in and induces a liquid-gas phase separation between a disordered gas and a ferromagnetic dense phase at low enough energies and large enough densities. The dynamics after a quench into the coexistence region show that the order parameter associated with the liquid-vapor phase separation follows an algebraic law with an unusual exponent, as it is forced to synchronize with the growth of the magnetization: this suggests that for finite size systems the magnetization sets in along a Curie line, which is also the gas-side spinodal line, and that the coexistence region ends at a tricritical point. This picture is confirmed at the mean-field level with different approximation schemes, namely, a Bethe lattice resolution and a virial expansion complemented by the introduction of a self-consistent Weiss-like molecular field. However, a detailed finite-size scaling analysis shows that in two dimensions the ferromagnetic phase escapes the Berezinskii-Kosterlitz-Thouless scenario and that the long-range order is not destroyed by the unbinding of topological defects. The Curie line thus becomes a magnetic crossover in the thermodynamic limit. Finally, the effects of the magnetic interaction range and those of the interaction softness are characterized within a mean-field semianalytical low-density approach.

Thermodynamic versus kinetic approach to polarization-vorticity coupling

We critically compare thermodynamic and kinetic approaches, that have been recently used to study relations between the spin polarization and fluid vorticity in systems consisting of spin-one-half particles. The thermodynamic approach refers to general properties of global thermal equilibrium with a rigid-like rotation and demonstrates that the spin-polarization and thermal-vorticity tensors are equal. On the other hand, the kinetic approach uses the concept of the Wigner function and its semi-classical expansion. In most of the works done so far, the Wigner functions satisfy kinetic equations with a vanishing collision term. We show that this assumption restricts significantly applicability of such frameworks and, in contrast to many claims found in the literature, does not allow for drawing any conclusions regarding the relation between the thermal-vorticity and spin-polarization tensors, except for the fact that the two should be constant in global equilibrium. We further show how the kinetic-theory equations including spin degrees of freedom can be used to formulate a hydrodynamic framework for particles with spin. We define hydrodynamic equations starting separately from the formulation by de~Groot, van~Leeuwen, and van~Weert and from the canonical formalism. In the former case the energy-momentum tensor is symmetric and the spin tensor is conserved, while in the later case the energy-momentum tensor is not symmetric and the spin tensor is not conserved. Nevertheless, in the two cases the total angular momentum is always conserved. Interestingly, the two approaches are connected by the pseudo-gauge transformation, which we explicitly define.

Residence time distribution in rapid multiphase reactors

Residence time distribution (RTD) provides information about average hydraulic residence time and the distribution of material in the reactor. A method for determining RTD for reactors with very short hydraulic residence times is deconvolution based on extraction of real RTD by the analysis of a non-ideal input signal. The mean residence time and dispersion were determined for the spinning fluids reactor (SFR). For the first time the deconvolution method was performed for a system where the tracer pulse signal is wider than actual RTD of the examined device. A prediction model for of the SFR was also developed, and validated.

Formulation of Mouth Dissolving Tablets Using Solid Dispersion Technique: A Review

Mouth-dissolving tablets are also called as fast disintegrating tablets, melt-in mouth tablets, orodispersible tablets, quick dissolving etc. Mouth dissolving tablets are those when put on tongue disintegrate rapidly thereby releasing the drug, which dissolve or disperses in the saliva. The faster the drug dissolved into solution, quick will be the absorption and onset of clinical effect. Mouth dissolving tablet containing solid dispersion was developed to improve the solubility of drug and stability of solid dispersion. Such tablets are disintegrate and/or dissolve rapidly in the saliva without the need for water. Hence it is regarded as the safest, most convenient and most economical method of drug delivery having the highest patient compliance. The later portion of the article focus on the progress in methods of manufacturing, evaluation and various latest technologies involved in the development of Mouth dissolving tablets. Solid dispersion is basically a drug with polymer two-component system; hence the drug–polymer interaction should be determined first in order to ensure the stability of the formulation. This review is intended to discuss the recent advances related on the area of solid dispersion technology. Since different methods are used for the preparation of solid dispersions such as fusion method, solvent method, melting solvent method, melt extrusion method, lyophilisation technique, melt agglomeration process, use of surfactant, electro spinning and super Critical Fluid Technology, of them which method is good and suitable for which type of drug. The use of Mouth dissolving dosage forms has solved various problems noted in administration of drugs to the pediatric and elderly patient, which constitutes a large proportion of the world's population. The initial focus of this review article is based on solid dispersion mainly advantages, disadvantages, types, the method of preparation, and characterization of the solid dispersion at laboratory and industrial level.

On the junction conditions in -gravity with torsion

Junction conditions are discussed within the framework of -gravity with torsion. After deriving general junction conditions, the cases of coupling to a Dirac field and a spin fluid are explicitly dealt with. The main differences with respect to Einstein–Cartan–Sciama–Kibble theory are outlined.

Does space-time torsion determine the minimum mass of gravitating particles?

We derive upper and lower limits for the mass–radius ratio of spin-fluid spheres in Einstein–Cartan theory, with matter satisfying a linear barotropic equation of state, and in the presence of a cosmological constant. Adopting a spherically symmetric interior geometry, we obtain the generalized continuity and Tolman–Oppenheimer–Volkoff equations for a Weyssenhoff spin fluid in hydrostatic equilibrium, expressed in terms of the effective mass, density and pressure, all of which contain additional contributions from the spin. The generalized Buchdahl inequality, which remains valid at any point in the interior, is obtained, and general theoretical limits for the maximum and minimum mass–radius ratios are derived. As an application of our results we obtain gravitational red shift bounds for compact spin-fluid objects, which may (in principle) be used for observational tests of Einstein–Cartan theory in an astrophysical context. We also briefly consider applications of the torsion-induced minimum mass to the spin-generalized strong gravity model for baryons/mesons, and show that the existence of quantum spin imposes a lower bound for spinning particles, which almost exactly reproduces the electron mass.

Quantum Spin Fluid Behaviors of the Kagome- and Triangular-Lattice Antiferromagnets

The S=1/2 kagome-lattice antiferromagnet is investigated using the numerical diagonalization of finite-size clusters. The analysis of the susceptibility at the zero magnetization indicates that the magnetic excitation of the system is gapless. It is consistent with our previous finite-scaling analysis of the spin gap. The application of the method for the triangular-lattice antiferromagnet confirms the validity of the analysis.

FAST DISSOLVING TABLET USING SOLID DISPERSION TECHNIQUE: A REVIEW

Fast dissolving tablets are also called as mouth-dissolving tablets, melt-in mouth tablets, orodispersible tablets, quick dissolving etc. Fast dissolving tablets are those when put on tongue disintegrate instantaneously releasing the drug, which dissolve or disperses in the saliva. The faster the drug dissolved into solution, quicker the absorption and onset of clinical effect. Oral routes of drug administration have wide acceptance up to 50-60% of total dosage forms. Fast dissolving tablet containing solid dispersion was developed to improve the dissolution of drug and stability of solid dispersion. They are disintegrating and/or dissolve rapidly in the saliva without the need for water. Thus it is regarded as the safest, most convenient and most economical method of drug delivery having the highest patient compliance. The later part of the article focus on the progress in methods of manufacturing, evaluation and various latest technologies involved in the development of Fast dissolving tablets. Solid dispersion is basically a drug–polymer two-component system; the drug–polymer interaction is the determining factor in its design and performance. It also discusses about modern characterization technique to characterize solid dispersion. In this review, it is intended to discuss the recent advances related on the area of solid dispersion technology. Different methods are also been used for preparation of solid dispersions such as Melting method, Solvent method, Melting solvent method, Melt extrusion method, lyophilisation Technique, Melt Agglomeration Process, The Use Of Surfactant, Electro spinning and Super Critical Fluid Technology. The introduction of fast dissolving dosage forms has solved some of the problems encountered in administration of drugs to the pediatric and elderly patient, which constitutes a large proportion of the world's population. Solid dispersions have attracted considerable interest as an efficient means of improving the dissolution rate and hence the bio availability of a range of poorly water-soluble drugs. The focus of one part of the review article is based on solid dispersion mainly advantages, disadvantages, types, the method of preparation, and characterization of the solid dispersion at laboratory and industrial level.

Frustrated spin-1/2 ladder with ferro- and antiferromagnetic legs

Two-leg spin-1/2 ladder systems consisting of a ferromagnetic leg and an antiferromagnetic leg are considered where the spins on the legs interact through antiferromagnetic rung couplings J1. These ladders can have two geometrical arrangements either zigzag or normal ladder and these systems are frustrated irrespective of their geometry. This frustration gives rise to incommensurate spin density wave, dimer and spin fluid phases in the ground state. The magnetization in the systems decreases linearly with J12, and the systems show an incommensurate phase for 0.0<J1<1.0. The spin-spin correlation functions in the incommensurate phase follow power law decay which is very similar to Heisenberg antiferromagnetic chain in external magnetic field. In large J1 limit, the normal ladder behaves like a collection of singlet dimers, whereas the zigzag ladder behaves as a one dimensional spin-1/2 antiferromagnetic chain.

A rare incidence of metal artifact on MRI.

We present a rare example of metal artifacts observed in magnetic resonance imaging (MRI). A 32-year-old male patient was referred to our radiology department for brain MRI. T1-weighted spin echo, T2-weighted turbo spin echo, diffusion-weighted, and fluid attenuated inversion recovery (FLAIR) images were acquired on a 1.5 Tesla scanner (Magnetom Aera, Siemens Erlangen, Germany). Unusual circular shapes resembling water bubbles were observed at the vertex on the conventional MR images ( Figure 1 ). The patient was contacted if he had anything on his head, such as hair gel, etc. during MR imaging. It was found out that the patient was a metal worker who cuts metals and shapes things out of them and there were residual metal dusts on his scalp despite he had a shower before coming to the hospital.

Axial dissipative dust as a source of gravitational radiation in f(R) gravity

Abstract In this paper, we explore the source of gravitational radiation in the context of f ( R ) gravity by considering axially symmetric dissipative dust under geodesic condition. We evaluate scalars associated with electric and magnetic parts of the Weyl tensor for both non-spinning (at the center) and spinning (in the surrounding of the center) fluids of the configuration. For this purpose, we use the evolution as well as constraint equations for kinematical quantities and Weyl tensor. Finally, we investigate the existence of gravitational radiation through super-Poynting vector. It is found that the fluid is not gravitationally radiating in the non-spinning case but it is gravitationally radiating for the spinning case.

UNIVERSE IN A BLACK HOLE IN EINSTEIN–CARTAN GRAVITY

ABSTRACT The conservation law for the angular momentum in curved spacetime, consistent with relativistic quantum mechanics, requires that the antisymmetric part of the affine connection (torsion tensor) is a variable in the principle of least action. The coupling between the spin of elementary particles and torsion in the Einstein–Cartan theory of gravity generates gravitational repulsion at extremely high densities in fermionic matter, approximated as a spin fluid, and thus avoids the formation of singularities in black holes. The collapsing matter in a black hole should therefore bounce at a finite density and then expand into a new region of space on the other side of the event horizon, which may be regarded as a nonsingular, closed universe. We show that quantum particle production caused by an extremely high curvature near a bounce can create enormous amounts of matter, produce entropy, and generate a finite period of exponential expansion (inflation) of this universe. This scenario can thus explain inflation without a scalar field and reheating. We show that, depending on the particle production rate, such a universe may undergo several nonsingular bounces until it has enough matter to reach a size at which the cosmological constant starts cosmic acceleration. The last bounce can be regarded as the big bang of this universe.

A coupled velocity and temperature problem of the extruded spinning column in a micro-extrusion

In this paper, we investigate a coupled velocity and temperature phase changing problem for a spinning extruded micro-column. Molten polymer is squeezed out from a spinning container in the form of a symmetrical column. The extruded and spinning fluid is being solidified through the heat exchange between the polymer in the solid state and the ambient environment resulting in a two phases (solid and liquid) problem. Temperature profile has previously been determined analytically using the boundary layer and lubrication theory techniques. However, the study on the effect of the moving boundary on the fluid flow in the liquid phase and the induced stress on the condensed shell remains absent. In this paper, we analytically deduce the velocity and stress profiles for different stages during the micro-extrusion process. Several simulations have also been performed to validate the assumptions made in the current mathematical model. We find that the velocity profile alters from certain quadratic flows into linear flows when the moving boundary retreats, and the surface stress alters from shear stress into the principal stress on the outer-shell accordingly. In conjunction with the centrifugal force induced by the spinning fluid acting on the shell, these provide some crucial factors for ensuring extruded products in their highest quality.

Ferromagnetic–ferromagnetic–antiferromagnetic–antiferromagnetic correlation and magnetization plateau in spin-1/2 J1–J1–J2–J2 tetrameric chains

The magnetization process of a spin-1/2 J1–J1–J2–J2 tetrameric Heisenberg chain is investigated by the infinite time-evolving block decimation (iTEBD) method. A magnetization phase diagram including three different phases, i.e., a fully polarized (FP) phase, a 1/2 plateau phase, and a spin-fluid (SF) phase, is obtained. All the quantum phase transitions (QPTs) are determined to belong to the second-order category, and the central charge in the critical SF phase equals 1. In addition, a 1/2 plateau phase also exists in the classical J1–J1–J2–J2 tetrameric Ising chain. The F–F–AF–AF (or AF–AF–F–F) type longitudinal correlation is found to be important and necessary for the appearance of the 1/2 plateau state in both quantum and classical cases.