A study of DINKIC inflationary dynamics with non-interacting imperfect fluid

2020 ◽  
Vol 35 (14) ◽  
pp. 2050108
Author(s):  
R. Saleem ◽  
Iqra Shahid ◽  
M. Zubair
Keyword(s):  
Correction Term ◽  
Field Potential ◽  
Large Field ◽  
Kinetic Term ◽  
Frw Universe ◽  
Scale Invariant ◽  
Kinetic Coupling ◽  
Proposed Model ◽  
Imperfect Fluid ◽  
Primordial Gravitational Waves

This paper is keen to study the generalized DBI-inspired non-minimal kinetic coupling inflationary model with non-interacting imperfect fluid in the framework of FRW universe. This is a newly proposed model with an interesting feature of having a correction term [Formula: see text] in the perturbed equation of motion due to the nonlinearity of the kinetic term. The power spectrum remains scale invariant both in large-[Formula: see text] and small-[Formula: see text] limits. In order to discuss the inflationary dynamics, the non-interacting inflaton and imperfect fluid including bulk viscosity are considered to be the cosmic matter contents. We consider large field potential and derive the exact solution of inflaton and perturbed parameters. Further, we investigate the nature of the perturbed parameters in detail, specifically on the potential-driven case, and compare the consequences to the current PLANCK/BICEP observational data. We also analyze the corresponding tensor spectrum, which will be tested by the future observations on primordial gravitational waves.

scholarly journals SSB OF SCALE SYMMETRY, FERMION FAMILIES AND QUINTESSENCE WITHOUT THE LONG-RANGE FORCE PROBLEM

2002 ◽  
Vol 17 (03) ◽  
pp. 417-433 ◽  
Author(s):  
E. I. GUENDELMAN ◽  
A. B. KAGANOVICH
Keyword(s):  
Particle Physics ◽  
Scale Invariance ◽  
Field Potential ◽  
Momentum Tensor ◽  
Kinetic Term ◽  
Exponential Potential ◽  
Scale Invariant ◽  
Fermion Masses ◽  
First Choice ◽  
Scaling Solution

We study a scale-invariant two measures theory where a dilaton field ϕ has no explicit potentials. The scale transformations include the translation of a dilaton ϕ→ϕ+ const . The theory demonstrates a new mechanism for generation of the exponential potential: in the conformal Einstein frame (CEF), after SSB of scale invariance, the theory develops the exponential potential and, in general, the nonlinear kinetic term is generated as well. The scale symmetry does not allow the appearance of terms breaking the exponential shape of the potential that solves the problem of the flatness of the scalar field potential in the context of quintessential scenarios. As examples, two different possibilities for the choice of the dimensionless parameters are presented where the theory permits to get interesting cosmological results. For the first choice, the theory has standard scaling solutions for ϕ usually used in the context of the quintessential scenario. For the second choice, the theory allows three different solutions, one of which is a scaling solution with equation of state pϕ=wρϕ where w is predicted to be restricted by -1<w<-0.82. The regime where the fermionic matter dominates (as compared to the dilatonic contribution) is analyzed. There it is found that starting from a single fermionic field we obtain exactly three different types of spin 1/2 particles in CEF that appears to suggest a new approach to the family problem of particle physics. It is automatically achieved that for two of them, fermion masses are constants, the energy–momentum tensor is canonical and the "fifth force" is absent. For the third type of particles, a fermionic self-interaction appears as a result of SSB of scale invariance.

scholarly journals Maintained avalanche dynamics during task-induced changes of neuronal activity in nonhuman primates

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Shan Yu ◽  
Tiago L Ribeiro ◽  
Christian Meisel ◽  
Samantha Chou ◽  
Andrew Mitz ◽  
...  
Keyword(s):  
Cognitive Processing ◽  
Neuronal Activity ◽  
Unit Activity ◽  
Scale Invariance ◽  
Nonhuman Primates ◽  
Field Potential ◽  
Scale Invariant ◽  
Ongoing Activity ◽  
Statistical Regularities ◽  
Induced Changes

Sensory events, cognitive processing and motor actions correlate with transient changes in neuronal activity. In cortex, these transients form widespread spatiotemporal patterns with largely unknown statistical regularities. Here, we show that activity associated with behavioral events carry the signature of scale-invariant spatiotemporal clusters, neuronal avalanches. Using high-density microelectrode arrays in nonhuman primates, we recorded extracellular unit activity and the local field potential (LFP) in premotor and prefrontal cortex during motor and cognitive tasks. Unit activity and negative LFP deflections (nLFP) consistently changed in rate at single electrodes during tasks. Accordingly, nLFP clusters on the array deviated from scale-invariance compared to ongoing activity. Scale-invariance was recovered using ‘adaptive binning’, that is identifying clusters at temporal resolution given by task-induced changes in nLFP rate. Measures of LFP synchronization confirmed and computer simulations detailed our findings. We suggest optimization principles identified for avalanches during ongoing activity to apply to cortical information processing during behavior.

scholarly journals On the structure of the magnetic field of sunspots

1968 ◽  
Vol 35 ◽  
pp. 215-229 ◽  
Author(s):  
E. I. Mogilevsky ◽  
L. B. Demkina ◽  
B. A. Ioshpa ◽  
V. N. Obridko
Keyword(s):  
Magnetic Field ◽  
Free Field ◽  
Large Field ◽  
Doppler Velocity ◽  
Small Scale ◽  
High Excitation ◽  
Proposed Model ◽  
Background Magnetic Field ◽  
Definition Of ◽  
The Magnetic Field

The model of the magnetic field of sunspots, taking account of fine structure of magnetic field in solar plasma, is considered. Small-scale subgranules with their own field form magnetic filaments in the external current-free field. The filaments are vertical in the umbra, while in the penumbra they run along the surface with sharp bends. In a number of spot umbra the relation between Doppler velocity and the field is established on polarized spectrograms. The π-component splitting in umbra is interpreted as a result of a weak background magnetic-field existence together with a large field of magnetic filaments. Spectrographic definition of the magnetic field in spot umbra is accomplished on the effect of magnetic-lines intensification and directly on spectrograms of low-excitation (Fe I, Ti I) and high-excitation (Fe II) lines. Magnetic field measured in low-excitation lines exceeds twice the field value obtained in high-excitation lines. This result has been considered in the light of the proposed model of sunspot field.

scholarly journals Deep Ego-Motion Classifiers for Compound Eye Cameras

Sensors ◽  
2019 ◽  
Vol 19 (23) ◽  
pp. 5275
Author(s):  
Hwiyeon Yoo ◽  
Geonho Cha ◽  
Songhwai Oh
Keyword(s):  
Compound Eye ◽  
Semantic Segmentation ◽  
Field Of View ◽  
Large Field ◽  
Light Weight ◽  
Unique Form ◽  
Motion Classification ◽  
Proposed Model ◽  
Compound Images ◽  
High Level

Compound eyes, also known as insect eyes, have a unique structure. They have a hemispheric surface, and a lot of single eyes are deployed regularly on the surface. Thanks to this unique form, using the compound images has several advantages, such as a large field of view (FOV) with low aberrations. We can exploit these benefits in high-level vision applications, such as object recognition, or semantic segmentation for a moving robot, by emulating the compound images that describe the captured scenes from compound eye cameras. In this paper, to the best of our knowledge, we propose the first convolutional neural network (CNN)-based ego-motion classification algorithm designed for the compound eye structure. To achieve this, we introduce a voting-based approach that fully utilizes one of the unique features of compound images, specifically, the compound images consist of a lot of single eye images. The proposed method classifies a number of local motions by CNN, and these local classifications which represent the motions of each single eye image, are aggregated to the final classification by a voting procedure. For the experiments, we collected a new dataset for compound eye camera ego-motion classification which contains scenes of the inside and outside of a certain building. The samples of the proposed dataset consist of two consequent emulated compound images and the corresponding ego-motion class. The experimental results show that the proposed method has achieved the classification accuracy of 85.0%, which is superior compared to the baselines on the proposed dataset. Also, the proposed model is light-weight compared to the conventional CNN-based image recognition algorithms such as AlexNet, ResNet50, and MobileNetV2.

scholarly journals Asymptotically Weyl-invariant gravity

2019 ◽  
Vol 34 (31) ◽  
pp. 1950205 ◽  
Author(s):  
Daniel Coumbe
Keyword(s):  
General Relativity ◽  
High Energy ◽  
Low Energy ◽  
Energy Limit ◽  
Scale Invariant ◽  
High Energy Limit ◽  
Palatini Formalism ◽  
A Value ◽  
Proposed Model ◽  
Novel Theory

We propose a novel theory of gravity that by construction is renormalizable, evades Ostrogradsky’s no-go theorem, is locally scale-invariant in the high-energy limit, and equivalent to general relativity in the low-energy limit. The theory is defined by a pure [Formula: see text] action in the Palatini formalism, where the dimensionless exponent [Formula: see text] runs from a value of two in the high-energy limit to one in the low-energy limit. We show that the proposed model contains no obvious cosmological curvature singularities. The viability of the proposed model is qualitatively assessed using several key criteria.

Evaluation and Analysis of Curvature-Corrected Filter-based Turbulent Model

2017 ◽  
Vol 34 (3) ◽  
Author(s):  
Rui Zhang
Keyword(s):  
Experimental Data ◽  
Numerical Calculation ◽  
Correction Term ◽  
Two Dimensional ◽  
Turbulent Model ◽  
Engineering Applications ◽  
Streamline Curvature ◽  
Naca0012 Airfoil ◽  
Proposed Model ◽  
Good Agreement

AbstractPrediction of the characteristics of turbulent flow with streamline curvature is of great importance in engineering applications. In this paper, a curvature-corrected filter-based turbulent model is suggested by applying the Spalart-Shur correction term. This new version of the model (FBM-CC) has been tested and verified through two canonical benchmarks with strong streamline curvature: the flow in a two-dimensional U-duct and the free shear flow past NACA0012 airfoil with a round tip. Predictions of the FBM-CC model are compared with available experimental data and the corresponding results of the original FBM model. The numerical results show that the FBM-CC model significantly improves the sensitivity to the effect of streamline curvature and the numerical calculation accuracy, in relatively good agreement with the experimental data, which suggests that this proposed model may be employed to simulate the turbulent curved flow in engineering applications.

scholarly journals A possible analogy between the dynamics of a skydiver and a scalar field: Cosmological consequences

2017 ◽  
Vol 27 (01) ◽  
pp. 1730026
Author(s):  
F. E. M. Costa
Keyword(s):  
Scalar Field ◽  
Field Potential ◽  
Quadratic Function ◽  
Terminal Velocity ◽  
Vertical Movement ◽  
Kinetic Term ◽  
Theoretical Predictions ◽  
Type Ia ◽  
Ia Supernovae ◽  
Slow Rolling

The cosmological consequences of a slow-rolling scalar field with constant kinetic term in analogy to the vertical movement of a skydiver after reaching terminal velocity are investigated. In this approach, the scalar field potential is given by a quadratic function of the field. This model provides solutions in which the universe was dominated in the past by a mixture of baryons and dark matter, is currently accelerating (as indicated by type Ia supernovae data), but will be followed by a contraction phase. The theoretical predictions of this model are consistent with current observations, therefore, a terminal scalar field is a viable candidate to dark energy.

scholarly journals Self-Organized Criticality in the Brain

2021 ◽  
Vol 9 ◽  
Author(s):  
Dietmar Plenz ◽  
Tiago L. Ribeiro ◽  
Stephanie R. Miller ◽  
Patrick A. Kells ◽  
Ali Vakili ◽  
...  
Keyword(s):  
Phase Transition ◽  
Order Phase Transition ◽  
Field Potential ◽  
Quiet Time ◽  
Scale Invariant ◽  
Self Organized ◽  
Up States ◽  
Self Organized Criticality ◽  
Neuronal Avalanches ◽  
The Brain

Self-organized criticality (SOC) refers to the ability of complex systems to evolve toward a second-order phase transition at which interactions between system components lead to scale-invariant events that are beneficial for system performance. For the last two decades, considerable experimental evidence has accumulated that the mammalian cortex with its diversity in cell types, interconnectivity, and plasticity might exhibit SOC. Here, we review the experimental findings of isolated, layered cortex preparations to self-organize toward four dynamical motifs presently identified in the intact cortex in vivo: up-states, oscillations, neuronal avalanches, and coherence potentials. During up-states, the synchronization observed for nested theta/gamma oscillations embeds scale-invariant neuronal avalanches, which can be identified by robust power law scaling in avalanche sizes with a slope of −3/2 and a critical branching parameter of 1. This precise dynamical coordination, tracked in the negative transients of the local field potential (nLFP) and spiking activity of pyramidal neurons using two-photon imaging, emerges autonomously in superficial layers of organotypic cortex cultures and acute cortex slices, is homeostatically regulated, exhibits separation of time scales, and reveals unique size vs. quiet time dependencies. A subclass of avalanches, the coherence potentials, exhibits precise maintenance of the time course in propagated local synchrony. Avalanches emerge in superficial layers of the cortex under conditions of strong external drive. The balance of excitation and inhibition (E/I), as well as neuromodulators such as dopamine, establishes powerful control parameters for avalanche dynamics. This rich dynamical repertoire is not observed in dissociated cortex cultures, which lack the differentiation into cortical layers and exhibit a dynamical phenotype expected for a first-order phase transition. The precise interactions between up-states, nested oscillations, and avalanches in superficial layers of the cortex provide compelling evidence for SOC in the brain.

scholarly journals Selective Participation of Single Cortical Neurons in Neuronal Avalanches

2021 ◽  
Vol 14 ◽  
Author(s):  
Timothy Bellay ◽  
Woodrow L. Shew ◽  
Shan Yu ◽  
Jessica J. Falco-Walter ◽  
Dietmar Plenz
Keyword(s):  
Information Processing ◽  
Cortical Neurons ◽  
Field Potential ◽  
High Temporal Resolution ◽  
Single Neurons ◽  
Scale Invariant ◽  
Neuronal Groups ◽  
Neuronal Avalanches

Neuronal avalanches are scale-invariant neuronal population activity patterns in the cortex that emerge in vivo in the awake state and in vitro during balanced excitation and inhibition. Theory and experiments suggest that avalanches indicate a state of cortex that improves numerous aspects of information processing by allowing for the transient and selective formation of local as well as system-wide spanning neuronal groups. If avalanches are indeed involved with information processing, one might expect that single neurons would participate in avalanche patterns selectively. Alternatively, all neurons could participate proportionally to their own activity in each avalanche as would be expected for a population rate code. Distinguishing these hypotheses, however, has been difficult as robust avalanche analysis requires technically challenging measures of their intricate organization in space and time at the population level, while also recording sub- or suprathreshold activity from individual neurons with high temporal resolution. Here, we identify repeated avalanches in the ongoing local field potential (LFP) measured with high-density microelectrode arrays in the cortex of awake nonhuman primates and in acute cortex slices from young and adult rats. We studied extracellular unit firing in vivo and intracellular responses of pyramidal neurons in vitro. We found that single neurons participate selectively in specific LFP-based avalanche patterns. Furthermore, we show in vitro that manipulating the balance of excitation and inhibition abolishes this selectivity. Our results support the view that avalanches represent the selective, scale-invariant formation of neuronal groups in line with the idea of Hebbian cell assemblies underlying cortical information processing.

scholarly journals Dynamical attractors in contracting spacetimes dominated by kinetically coupled scalar fields

2021 ◽  
Vol 2021 (12) ◽  
pp. 030
Author(s):  
Anna Ijjas ◽  
Frans Pretorius ◽  
Paul J. Steinhardt ◽  
David Garfinkle
Keyword(s):  
Scalar Field ◽  
Initial Conditions ◽  
Scalar Fields ◽  
Density Fluctuations ◽  
Microwave Background ◽  
Scale Invariant ◽  
Linear Evolution ◽  
Kinetic Coupling ◽  
Wide Range ◽  
Non Linear

Abstract We present non-perturbative numerical relativity simulations of slowly contracting spacetimes in which the scalar field driving slow contraction is coupled to a second scalar field through an exponential non-linear σ model-type kinetic interaction. These models are important because they can generate a nearly scale-invariant spectrum of super-Hubble density fluctuations fully consistent with cosmic microwave background observations. We show that the non-linear evolution rapidly approaches a homogeneous, isotropic and flat Friedmann-Robertson-Walker (FRW) geometry for a wide range of inhomogeneous and anisotropic initial conditions. Ultimately, we find, the kinetic coupling causes the evolution to deflect away from flat FRW and towards a novel Kasner-like stationary point, but in general this occurs on time scales that are too long to be observationally relevant.

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