keyword
MENU ▼
Read by QxMD icon Read
search

Planck space

keyword
https://www.readbyqxmd.com/read/29391499/chaos-and-dynamical-complexity-in-the-quantum-to-classical-transition
#1
Bibek Pokharel, Moses Z R Misplon, Walter Lynn, Peter Duggins, Kevin Hallman, Dustin Anderson, Arie Kapulkin, Arjendu K Pattanayak
We study the largest Lyapunov exponents λ and dynamical complexity for an open quantum driven double-well oscillator, mapping its dependence on coupling to the environment Γ as well as effective Planck's constant β2. We show that in general λ increases with effective Hilbert space size (as β decreases, or the system becomes larger and closer to the classical limit). However, if the classical limit is regular, there is always a quantum system with λ greater than the classical λ, with several examples where the quantum system is chaotic even though the classical system is regular...
February 1, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29382874/phase-space-volume-scaling-of-generalized-entropies-and-anomalous-diffusion-scaling-governed-by-corresponding-non-linear-fokker-planck-equations
#2
Dániel Czégel, Sámuel G Balogh, Péter Pollner, Gergely Palla
Many physical, biological or social systems are governed by history-dependent dynamics or are composed of strongly interacting units, showing an extreme diversity of microscopic behaviour. Macroscopically, however, they can be efficiently modeled by generalizing concepts of the theory of Markovian, ergodic and weakly interacting stochastic processes. In this paper, we model stochastic processes by a family of generalized Fokker-Planck equations whose stationary solutions are equivalent to the maximum entropy distributions according to generalized entropies...
January 30, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29347760/anomalies-in-the-equilibrium-and-nonequilibrium-properties-of-correlated-ions-in-complex-molecular-environments
#3
Sathiya Mahakrishnan, Subrata Chakraborty, Amrendra Vijay
Emergent statistical attributes, and therefore the equations of state, of an assembly of interacting charge carriers embedded within a complex molecular environment frequently exhibit a variety of anomalies, particularly in the high-density (equivalently, the concentration) regime, which are not well understood, because they do not fall under the low-concentration phenomenologies of Debye-Hückel-Onsager and Poisson-Nernst-Planck, including their variants. To go beyond, we here use physical concepts and mathematical tools from quantum scattering theory, transport theory with the Stosszahlansatz of Boltzmann, and classical electrodynamics (Lorentz gauge) and obtain analytical expressions both for the average and the frequency-wave vector-dependent longitudinal and transverse current densities, diffusion coefficient, and the charge density, and therefore the analytical expressions for (a) the chemical potential, activity coefficient, and the equivalent conductivity for strong electrolytes and (b) the current-voltage characteristics for ion-transport processes in complex molecular environments...
November 2017: Physical Review. E
https://www.readbyqxmd.com/read/29347715/cusps-enable-line-attractors-for-neural-computation
#4
Zhuocheng Xiao, Jiwei Zhang, Andrew T Sornborger, Louis Tao
Line attractors in neuronal networks have been suggested to be the basis of many brain functions, such as working memory, oculomotor control, head movement, locomotion, and sensory processing. In this paper, we make the connection between line attractors and pulse gating in feed-forward neuronal networks. In this context, because of their neutral stability along a one-dimensional manifold, line attractors are associated with a time-translational invariance that allows graded information to be propagated from one neuronal population to the next...
November 2017: Physical Review. E
https://www.readbyqxmd.com/read/29347544/adiabatic-elimination-of-inertia-of-the-stochastic-microswimmer-driven-by-%C3%AE-stable-noise
#5
Joerg Noetel, Igor M Sokolov, Lutz Schimansky-Geier
We consider a microswimmer that moves in two dimensions at a constant speed and changes the direction of its motion due to a torque consisting of a constant and a fluctuating component. The latter will be modeled by a symmetric Lévy-stable (α-stable) noise. The purpose is to develop a kinetic approach to eliminate the angular component of the dynamics to find a coarse-grained description in the coordinate space. By defining the joint probability density function of the position and of the orientation of the particle through the Fokker-Planck equation, we derive transport equations for the position-dependent marginal density, the particle's mean velocity, and the velocity's variance...
October 2017: Physical Review. E
https://www.readbyqxmd.com/read/29341784/fractional-transport-in-strongly-turbulent-plasmas
#6
Heinz Isliker, Loukas Vlahos, Dana Constantinescu
We analyze statistically the energization of particles in a large scale environment of strong turbulence that is fragmented into a large number of distributed current filaments. The turbulent environment is generated through strongly perturbed, 3D, resistive magnetohydrodynamics simulations, and it emerges naturally from the nonlinear evolution, without a specific reconnection geometry being set up. Based on test-particle simulations, we estimate the transport coefficients in energy space for use in the classical Fokker-Planck (FP) equation, and we show that the latter fails to reproduce the simulation results...
July 28, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/29146422/numerical-study-of-the-effect-of-soft-layer-properties-on-bacterial-electroporation
#7
Jeffrey L Moran, Naga Neehar Dingari, Paulo A Garcia, Cullen R Buie
We present a numerical model of electroporation in a gram-positive bacterium, which accounts for the presence of a negatively charged soft polyelectrolyte layer (which may include a periplasmic space, peptidoglycan layer, cilia, flagella, and other surface appendages) surrounding its plasma membrane. We model the ion transport within and outside the soft layer using the soft layer electrokinetics-based Poisson-Nernst-Planck formalism. Additionally, we model the electroporation dynamics on the plasma membrane using the pore nucleation-based electroporation formalism developed by Krassowska and Filev...
September 18, 2017: Bioelectrochemistry
https://www.readbyqxmd.com/read/29101341/quantum-mechanics-as-classical-statistical-mechanics-with-an-ontic-extension-and-an-epistemic-restriction
#8
Agung Budiyono, Daniel Rohrlich
Where does quantum mechanics part ways with classical mechanics? How does quantum randomness differ fundamentally from classical randomness? We cannot fully explain how the theories differ until we can derive them within a single axiomatic framework, allowing an unambiguous account of how one theory is the limit of the other. Here we derive non-relativistic quantum mechanics and classical statistical mechanics within a common framework. The common axioms include conservation of average energy and conservation of probability current...
November 3, 2017: Nature Communications
https://www.readbyqxmd.com/read/28991743/curvature-integration-in-a-5d-kernel-for-extracting-vessel-connections-in-retinal-images
#9
Samaneh Abbasi-Sureshjani, Marta Favali, Giovanna Citti, Alessandro Sarti, Bart M Ter Haar Romeny
Tree-like structures such as retinal images are widely studied in computer-aided diagnosis systems for large-scale screening programs. Despite several segmentation and tracking methods proposed in the literature, there still exist several limitations specifically when two or more curvilinear structures cross or bifurcate, or in the presence of interrupted lines or highly curved blood vessels. In this paper, we propose a novel approach based on multi-orientation scores augmented with a contextual affinity matrix, which both are inspired by the geometry of the primary visual cortex (V1) and their contextual connections...
October 9, 2017: IEEE Transactions on Image Processing: a Publication of the IEEE Signal Processing Society
https://www.readbyqxmd.com/read/28949174/no-evidence-for-extensions-to-the-standard-cosmological-model
#10
Alan Heavens, Yabebal Fantaye, Elena Sellentin, Hans Eggers, Zafiirah Hosenie, Steve Kroon, Arrykrishna Mootoovaloo
We compute the Bayesian evidence for models considered in the main analysis of Planck cosmic microwave background data. By utilizing carefully defined nearest-neighbor distances in parameter space, we reuse the Monte Carlo Markov chains already produced for parameter inference to compute Bayes factors B for many different model-data set combinations. The standard 6-parameter flat cold dark matter model with a cosmological constant (ΛCDM) is favored over all other models considered, with curvature being mildly favored only when cosmic microwave background lensing is not included...
September 8, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28891501/a-comparison-of-computational-models-for-the-extracellular-potential-of-neurons
#11
Jurgis Pods
The extracellular space has an ambiguous role in neuroscience. It is present in every physiologically relevant system and often used as a measurement site in experimental recordings, but it has received subordinate attention compared to the intracellular domain. In computational modeling, it is often regarded as a passive, homogeneous resistive medium with a constant conductivity, which greatly simplifies the computation of extracellular potentials. However, novel studies have shown that local ionic diffusion and capacitive effects of electrically active membranes can have a substantial impact on the extracellular potential...
2017: Journal of Integrative Neuroscience
https://www.readbyqxmd.com/read/28863683/portable-double-sided-pulsed-laser-heating-system-for-time-resolved-geoscience-and-materials-science-applications
#12
G Aprilis, C Strohm, I Kupenko, S Linhardt, A Laskin, D M Vasiukov, V Cerantola, E G Koemets, C McCammon, A Kurnosov, A I Chumakov, R Rüffer, N Dubrovinskaia, L Dubrovinsky
A portable double-sided pulsed laser heating system for diamond anvil cells has been developed that is able to stably produce laser pulses as short as a few microseconds with repetition frequencies up to 100 kHz. In situ temperature determination is possible by collecting and fitting the thermal radiation spectrum for a specific wavelength range (particularly, between 650 nm and 850 nm) to the Planck radiation function. Surface temperature information can also be time-resolved by using a gated detector that is synchronized with the laser pulse modulation and space-resolved with the implementation of a multi-point thermal radiation collection technique...
August 2017: Review of Scientific Instruments
https://www.readbyqxmd.com/read/28810751/communication-on-the-diffusion-tensor-in-macroscopic-theory-of-cavitation
#13
Vitaly A Shneidman
The classical description of nucleation of cavities in a stretched fluid relies on a one-dimensional Fokker-Planck equation (FPE) in the space of their sizes r, with the diffusion coefficient D(r) constructed for all r from macroscopic hydrodynamics and thermodynamics, as shown by Zeldovich. When additional variables (e.g., vapor pressure) are required to describe the state of a bubble, a similar approach to construct a diffusion tensor D^ generally works only in the direct vicinity of the thermodynamic saddle point corresponding to the critical nucleus...
August 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28709295/classical-counterparts-of-quantum-attractors-in-generic-dissipative-systems
#14
Gabriel G Carlo, Leonardo Ermann, Alejandro M F Rivas, María E Spina, Dario Poletti
In the context of dissipative systems, we show that for any quantum chaotic attractor a corresponding classical chaotic attractor can always be found. We provide a general way to locate them, rooted in the structure of the parameter space (which is typically bidimensional, accounting for the forcing strength and dissipation parameters). In cases where an approximate pointlike quantum distribution is found, it can be associated with exceptionally large regular structures. Moreover, supposedly anomalous quantum chaotic behavior can be very well reproduced by the classical dynamics plus Gaussian noise of the size of an effective Planck constant ℏ_{eff}...
June 2017: Physical Review. E
https://www.readbyqxmd.com/read/28688401/probing-photoisomerization-processes-by-means-of-multi-dimensional-electronic-spectroscopy-the-multi-state-quantum-hierarchical-fokker-planck-equation-approach
#15
Tatsushi Ikeda, Yoshitaka Tanimura
Photoisomerization in a system with multiple electronic states and anharmonic potential surfaces in a dissipative environment is investigated using a rigorous numerical method employing quantum hierarchical Fokker-Planck equations (QHFPEs) for multi-state systems. We have developed a computer code incorporating QHFPE for general-purpose computing on graphics processing units that can treat multi-state systems in phase space with any strength of diabatic coupling of electronic states under non-perturbative and non-Markovian system-bath interactions...
July 7, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28674453/on-noise-resolution-uncertainty-in-quantum-field-theory
#16
Timur E Gureyev, Alexander Kozlov, Yakov I Nesterets, David M Paganin, Harry M Quiney
An uncertainty inequality is presented that establishes a lower limit for the product of the variance of the time-averaged intensity of a mode of a quantized electromagnetic field and the degree of its spatial localization. The lower limit is determined by the vacuum fluctuations within the volume corresponding to the width of the mode. This result also leads to a generalized form of the Heisenberg uncertainty principle for boson fields in which the lower limit for the product of uncertainties in the spatial and momentum localization of a mode is equal to the product of Planck's constant and a dimensionless functional which reflects the joint signal-to-noise ratio of the position and momentum of vacuum fluctuations in the region of the phase space occupied by the mode...
July 3, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28644841/low-dimensional-spike-rate-models-derived-from-networks-of-adaptive-integrate-and-fire-neurons-comparison-and-implementation
#17
COMPARATIVE STUDY
Moritz Augustin, Josef Ladenbauer, Fabian Baumann, Klaus Obermayer
The spiking activity of single neurons can be well described by a nonlinear integrate-and-fire model that includes somatic adaptation. When exposed to fluctuating inputs sparsely coupled populations of these model neurons exhibit stochastic collective dynamics that can be effectively characterized using the Fokker-Planck equation. This approach, however, leads to a model with an infinite-dimensional state space and non-standard boundary conditions. Here we derive from that description four simple models for the spike rate dynamics in terms of low-dimensional ordinary differential equations using two different reduction techniques: one uses the spectral decomposition of the Fokker-Planck operator, the other is based on a cascade of two linear filters and a nonlinearity, which are determined from the Fokker-Planck equation and semi-analytically approximated...
June 2017: PLoS Computational Biology
https://www.readbyqxmd.com/read/28641254/sparse-image-reconstruction-on-the-sphere-analysis-and-synthesis
#18
Christopher G R Wallis, Yves Wiaux, Jason D McEwen
We develop techniques to solve ill-posed inverse problems on the sphere by sparse regularisation, exploiting sparsity in both axisymmetric and directional scale-discretised wavelet space. Denoising, inpainting, and deconvolution problems, and combinations thereof, are considered as examples. Inverse problems are solved in both the analysis and synthesis settings, with a number of different sampling schemes. The most effective approach is that with the most restricted solution-space, which depends on the interplay between the adopted sampling scheme, the selection of the analysis/synthesis problem, and any weighting of the ℓ1 norm appearing in the regularisation problem...
June 16, 2017: IEEE Transactions on Image Processing: a Publication of the IEEE Signal Processing Society
https://www.readbyqxmd.com/read/28571349/asymmetric-osmotic-water-permeation-through-a-vesicle-membrane
#19
Jiaye Su, Yunzhen Zhao, Chang Fang, Yue Shi
Understanding the water permeation through a cell membrane is of primary importance for biological activities and a key step to capture its shape transformation in salt solution. In this work, we reveal the dynamical behaviors of osmotically driven transport of water molecules across a vesicle membrane by molecular dynamics simulations. Of particular interest is that the water transport in and out of vesicles is highly distinguishable given the osmotic force are the same, suggesting an asymmetric osmotic transportation...
May 28, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28452515/classical-fractals-and-quantum-chaos-in-ultracold-dipolar-collisions
#20
B C Yang, Jesús Pérez-Ríos, F Robicheaux
We examine a dipolar-gas model to address fundamental issues regarding the correspondence between classical chaos and quantum observations in ultracold dipolar collisions. The theoretical model consists of a short-range Lennard-Jones potential well with an anisotropic, long-range dipole-dipole interaction between two atoms. Both the classical and quantum dynamics are explored for the same Hamiltonian of the system. The classical chaotic scattering is revealed by the fractals developed in the scattering function (defined as the final atom separation as a function of initial conditions), while the quantum chaotic features lead to the repulsion of the eigenphases from the corresponding quantum S matrix...
April 14, 2017: Physical Review Letters
keyword
keyword
12064
1
2
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read
×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"