Expanding models with a varying cosmological term and bulk stress

1996 ◽  
Vol 28 (6) ◽  
pp. 679-689 ◽  
Author(s):  
Vicenç Méndez ◽  
Diego Pavón
Keyword(s):  
Cosmological Term ◽  
Bulk Stress

ON A PERFECT FLUID K¨ AHLER SPACETIME

2016 ◽  
Vol 12 (3) ◽  
pp. 4350-4355
Author(s):  
VIBHA SRIVASTAVA ◽  
P. N. PANDEY
Keyword(s):  
Field Equation ◽  
Perfect Fluid ◽  
Sectional Curvature ◽  
Einstein Field Equation ◽  
Cosmological Term ◽  
Conformal Killing ◽  
Killing Vectors ◽  
Projectively Flat ◽  
Conformal Killing Vectors

The object of the present paper is to study a perfect fluid K¨ahlerspacetime. A perfect fluid K¨ahler spacetime satisfying the Einstein field equation with a cosmological term has been studied and the existence of killingand conformal killing vectors have been discussed. Certain results related to sectional curvature for pseudo projectively flat perfect fluid K¨ahler spacetime have been obtained. Dust model for perfect fluid K¨ahler spacetime has also been studied.

scholarly journals Defect CFT techniques in the 6d $$ \mathcal{N} $$ = (2, 0) theory

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Nadav Drukker ◽  
Malte Probst ◽  
Maxime Trépanier
Keyword(s):  
Stress Tensor ◽  
Unitary Representations ◽  
Point Function ◽  
Displacement Operator ◽  
Expectation Value ◽  
Operator Expansion ◽  
Bulk Stress ◽  
Defect Operator ◽  
Tensor Multiplet

Abstract Surface operators are among the most important observables of the 6d $$ \mathcal{N} $$ N = (2, 0) theory. Here we apply the tools of defect CFT to study local operator insertions into the 1/2-BPS plane. We first relate the 2-point function of the displacement operator to the expectation value of the bulk stress tensor and translate this relation into a constraint on the anomaly coefficients associated with the defect. Secondly, we study the defect operator expansion of the stress tensor multiplet and identify several new operators of the defect CFT. Technical results derived along the way include the explicit supersymmetry tranformations of the stress tensor multiplet and the classification of unitary representations of the superconformal algebra preserved by the defect.

scholarly journals Generalized supersymmetric cosmological term in N=1 supergravity

2015 ◽  
Vol 2015 (8) ◽  
Author(s):  
P. K. Concha ◽  
E. K. Rodríguez ◽  
P. Salgado
Keyword(s):  
Cosmological Term

scholarly journals Almost-Pseudo-Ricci Symmetric FRW Universe with a Dynamic Cosmological Term and Equation of State

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 205
Author(s):  
Sanjay Mandal ◽  
Avik De ◽  
Tee-How Loo ◽  
Pradyumn Kumar Sahoo
Keyword(s):  
Equation Of State ◽  
Cosmological Parameters ◽  
Cosmological Term ◽  
Ricci Scalar ◽  
Energy Conditions ◽  
Late Time ◽  
Frw Universe ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Universe

The objective of the present paper is to investigate an almost-pseudo-Ricci symmetric FRW spacetime with a constant Ricci scalar in a dynamic cosmological term Λ(t) and equation of state (EoS) ω(t) scenario. Several cosmological parameters are calculated in this setting and thoroughly studied, which shows that the model satisfies the late-time accelerating expansion of the universe. We also examine all of the energy conditions to check our model’s self-stability.

Nondestructive Photoelastic and Machine Learning Characterization of Surface Cracks and Prediction of Weibull Parameters for Photovoltaic Silicon Wafers

2021 ◽  
pp. 1-40
Author(s):  
Logan Rowe ◽  
Alexander J. Kaczkowski ◽  
Tung-Wei Lin ◽  
Gavin Horn ◽  
Harley Johnson
Keyword(s):  
Machine Learning ◽  
Learning Algorithm ◽  
Tensile Load ◽  
Silicon Wafers ◽  
Uniaxial Tensile ◽  
Support Vector ◽  
Weibull Parameters ◽  
Bulk Stress ◽  
Wire Motion

Abstract A nondestructive photoelastic method is presented for characterizing surface microcracks in monocrystalline silicon wafers, calculating the strength of the wafers, and predicting Weibull parameters under various loading conditions. Defects are first classified from through thickness infrared photoelastic images using a support vector machine learning algorithm. Characteristic wafer strength is shown to vary with the angle of applied uniaxial tensile load, showing greater strength when loaded perpendicular to the direction of wire motion than when loaded along the direction of wire motion. Observed variations in characteristic strength and Weibull shape modulus with applied tensile loading direction stem from the distribution of crack orientations and the bulk stress field acting on the microcracks. Using this method it is possible to improve manufacturing processes for silicon wafers by rapidly, accurately, and nondestructively characterizing large batches in an automated way.

The stress generated in a non-dilute suspension of elongated particles by pure straining motion

1971 ◽  
Vol 46 (4) ◽  
pp. 813-829 ◽  
Author(s):  
G. K. Batchelor
Keyword(s):  
Theoretical Formula ◽  
Rigid Sphere ◽  
Cross Sectional ◽  
Outer Flow ◽  
Rigid Particles ◽  
Bulk Stress ◽  
Order Of Magnitude ◽  
Sectional Plane ◽  
Dilute Suspension ◽  
A Minor

In a pure straining motion, elongated rigid particles in suspension are aligned parallel to the direction of the greatest principal rate of extension, provided the effect of Brownian motion is weak. If the suspension is dilute, in the sense that the particles are hydrodynamically independent, each particle of length 2l makes a contribution to the bulk deviatoric stress which is of roughly the same order of magnitude as that due to a rigid sphere of radius l. The fractional increase in the bulk stress due to the presence of the particles is thus equal to the concentration by volume multiplied by a factor of order l2/b2, where 2b is a measure of the linear dimensions of the particle cross-section. This suggests that the stress due to the particles might be relatively large, for volume fractions which are still small, with interesting implications for the behaviour of polymer solutions. However, dilute-suspension theory is not applicable in these circumstances, and so an investigation is made of the effect of interactions between particles. It is assumed that, when the average lateral spacing of particles (h) satisfies the conditions b [Lt ] h [Lt ] l, the disturbance velocity vector is parallel to the particles and varies only in the cross-sectional plane. The velocity near a particle is found to have the same functional form as for an isolated particle, and the modification to the outer flow field for one particle is determined by replacing the randomly placed neighbouring particles by an equivalent cylindrical boundary. The resulting expression for the contribution to the bulk stress due to the particles differs from that for a dilute suspension only in a minor way, viz. by the replacement of log 2l/b by log h/b, and the above suggestion is confirmed. The relative error in the expression for the stress is expected to be of order (log h/b)−1. Some recent observations by Weinberger of the stress in a suspension of glass-fibre particles for which 2l/h = 7·4 and h/2b = 7·8 do show a particle stress which is much larger than the ambient-fluid stress, although the theoretical formula is not accurate under these conditions.

The cosmological term, compensation and singularities

1974 ◽  
Vol 17 (12) ◽  
pp. 1661-1666
Author(s):  
D. D. Ivanenko
Keyword(s):  
Cosmological Term

scholarly journals Dynamics and stability of skyrmions in a bended nano-beam

2021 ◽  
Author(s):  
Anruo Zhong ◽  
Xiaoming Lan ◽  
Yangfan Hu ◽  
Biao Wang
Keyword(s):  
Energy Cost ◽  
High Mobility ◽  
Bending Moment ◽  
Elastic Fields ◽  
Spintronic Devices ◽  
Bulk Stress ◽  
The Stability ◽  
Magnetic Skyrmions ◽  
Nontrivial Topology ◽  
A Current

Abstract Magnetic skyrmions are attracting much attention due to their nontrivial topology and high mobility to electric current. Nevertheless, suppression of the skyrmion Hall effect and maintaining high velocity of skyrmions with low energy cost are two major challenges concerning skyrmion-based spintronic devices. Here we show theoretically that in a nano-beam suffering appropriate bending moment, both Bloch-type and Néel-type skyrmions move with a vanishing Hall angle under a current density smaller than that required when the bending is absent. Moreover, bending alone can be used to move skyrmions, whose velocity is solved analytically from the Thiele equation. Generally speaking, inhomogeneous elastic fields affect the stability and dynamics of skyrmions, where the local stability is dominantly determined by the local bulk stress. These findings throw new light on how to drive skyrmions straightly with lower energy cost, which is vital for utilizing skyrmions as information carriers.

scholarly journals Effect of wearing diapers on toddler’s gait

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tomoya Ueda ◽  
Haruna Asano ◽  
Kyoko Tsuge ◽  
Kanako Seo ◽  
Motoki Sudo ◽  
...  
Keyword(s):  
Motor Development ◽  
Joint Angle ◽  
Step Length ◽  
Step Width ◽  
Lower Stress ◽  
Gait Patterns ◽  
Bulk Stress ◽  
Joint Dynamics ◽  
Spatiotemporal Parameters ◽  
High Bulk

AbstractGait maturation in infants develops gradually through several phases. However, external factors such as childrearing practices, especially the wearing of diapers, may affect an infant’s motor development. This study investigated the influence of different bulk stresses on the gait of toddlers wearing a disposable diaper. Twenty-six healthy toddlers (age: 19.2 ± 0.9 months) participated in this study. We measured the joint kinematics (pelvis angle and hip-joint angle) and spatiotemporal parameters (step length and step width) of the toddlers’ gait under four dress conditions (wearing Type A_WET, Type A_DRY, and Type B_WET diapers and naked). Type B_WET had a higher bulk stress than Type A_WET, and Type A_DRY had lower stress than Type A _ WET. Our results indicate that the walk of toddlers when wearing a diaper differs from that when naked. This difference is due to the effect of the bulk of the diaper on the lower limb. A high bulk stress has a greater influence than that of a low bulk stress on joint dynamics and step width. Therefore, our findings suggest that wearing diapers with high bulk stress may inhibit the natural gait patterns of toddlers.

Impurity spectra in germanium due to bulk stress from surface strain

2001 ◽  
Vol 302-303 ◽  
pp. 317-326 ◽  
Author(s):  
P Fisher ◽  
B.D Crowe ◽  
R.E.M Vickers ◽  
A.B Rosenfeld
Keyword(s):  
Surface Strain ◽  
Bulk Stress
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