Fermi velocity reduction in graphene due to enhanced vacuum fluctuations

Author(s):  
Federico Nahuel Escudero ◽  
Juan Sebastian Ardenghi
Author(s):  
Michael Kachelriess

The contribution of vacuum fluctuations to the cosmological constant is reconsidered studying the dependence on the used regularisation scheme. Then alternative explanations for the observed accelerated expansion of the universe in the present epoch are introduced which either modify gravity or add a new component of matter, dubbed dark energy. The chapter closes with some comments on attempts to quantise gravity.


Author(s):  
Neng Wan ◽  
Guangping Zeng ◽  
Chunguang Zhang ◽  
Dingqi Pan ◽  
Songtao Cai

This paper deals with a new state-constrained control (SCC) system of vehicle, which includes a multi-layer controller, in order to ensure the vehicle’s lateral stability and steering performance under complex environment. In this system, a new constraint control strategy with input and state constraints is applied to calculate the steady-state yaw moment. It ensures the vehicle lateral stability by tracking the desired yaw rate value and limiting the allowable range of the side slip. Through the linkage of the three-layer controller, the tire load is optimized and achieve minimal vehicle velocity reduction. The seven-degree-of-freedom (7-DOF) simulation model was established and simulated in MATLAB to evaluate the effect of the proposed controller. Through the analysis of the simulation results, compared with the traditional ESC and integrated control, it not only solves the problem of obvious velocity reduction, but also solves the problem of high cost and high hardware requirements in integrated control. The simulation results show that designed control system has better performance of path tracking and driving state, which is closer to the desired value. Through hardware-in-the-loop (HIL) practical experiments in two typical driving conditions, the effectiveness of the above proposed control system is further verified, which can improve the lateral stability and maneuverability of the vehicle.


2021 ◽  
Vol 51 (3) ◽  
Author(s):  
Gerard ’t Hooft

AbstractFast moving classical variables can generate quantum mechanical behavior. We demonstrate how this can happen in a model. The key point is that in classically (ontologically) evolving systems one can still define a conserved quantum energy. For the fast variables, the energy levels are far separated, such that one may assume these variables to stay in their ground state. This forces them to be entangled, so that, consequently, the slow variables are entangled as well. The fast variables could be the vacuum fluctuations caused by unknown super heavy particles. The emerging quantum effects in the light particles are expressed by a Hamiltonian that can have almost any form. The entire system is ontological, and yet allows one to generate interference effects in computer models. This seemed to lead to an inexplicable paradox, which is now resolved: exactly what happens in our models if we run a quantum interference experiment in a classical computer is explained. The restriction that very fast variables stay predominantly in their ground state appears to be due to smearing of the physical states in the time direction, preventing their direct detection. Discussions are added of the emergence of quantum mechanics, and the ontology of an EPR/Bell Gedanken experiment.


2012 ◽  
Vol 26 (31) ◽  
pp. 1250210 ◽  
Author(s):  
M. A. GRADO-CAFFARO ◽  
M. GRADO-CAFFARO

The optical potential of an attractive nonrelativistic electron gas interacting with nuclear matter is determined on the basis of the concept of degenerate Fermi gas. In fact, the involved electrons are treated as three-dimensional quantum harmonic oscillators confined at the surface of a spherical (approximately ideal) potential well. Within this picture, the Fermi velocity is calculated as well as the spatial electron density at the surface of the potential well and the attractive force between the electron gas and the nuclear matter. In addition, considerations related to the Lippmann–Schwinger model are made.


JETP Letters ◽  
2011 ◽  
Vol 94 (7) ◽  
pp. 565-569 ◽  
Author(s):  
Yu. V. Skrypnyk ◽  
V. M. Loktev

2013 ◽  
Vol 28 (03) ◽  
pp. 1340015 ◽  
Author(s):  
LANCE LABUN ◽  
JOHANN RAFELSKI

The electron vacuum fluctuations measured by [Formula: see text] do not vanish in an externally applied electric field ℰ. For an exactly constant field, that is for vacuum fluctuations in presence of a constant accelerating force, we show that [Formula: see text] has a Boson-like structure with spectral state density tanh -1(E/m) and temperature T M = eℰ/mπ = av/π. Considering the vacuum fluctuations of 'classical' gyromagnetic ratio g = 1 particles we find Fermi-like structure with the same spectral state density at a smaller temperature T1 = av/2π which corresponds to the Unruh temperature of an accelerated observer.


2002 ◽  
Vol 66 (6) ◽  
Author(s):  
L. H. Ford ◽  
N. F. Svaiter
Keyword(s):  

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