The interaction of kinks and elastic waves

1962 ◽  
Vol 266 (1325) ◽  
pp. 222-246 ◽  
Keyword(s):  
Energy Density ◽  
Cross Section ◽  
Elastic Waves ◽  
String Model ◽  
Zero Point ◽  
Radiation Reaction ◽  
Point Energy ◽  
A Value ◽  
Ordinary Point ◽  
Isotropic Elastic Medium

A kink on a dislocation in an isotropic elastic medium is treated as a 'point defect’ with a certain mass, constrained to move along a line and subject to a radiation reaction. A value for the mass is obtained from the well know n stretched-string model, and the radiation reaction is found by calculating the rate at which an oscillating kink radiates energy into the medium . It is found that the kink has a scattering cross-section for elastic waves which i§ proportional to the square of its width. For long waves the cross-section is independent of frequency, in contrast to the case of ordinary point defects. A kink moving through an isotropic flux of elastic waves experiences a retarding force proportional to the product of its velocity and the energy density of the waves. In connexion with a similar result for the retarding force on a dislocation moving rigidly it has been suggested that the expression for the energy density should include the zero-point energy. A formal quantum -mechanical calculation shows that this is not so in the case of a kink.

Dark energy and dark matter as due to zero point energy

2012 ◽  
Vol 79 (3) ◽  
pp. 327-334 ◽  
Author(s):  
BO LEHNERT
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Energy Density ◽  
Vacuum Energy ◽  
Mass Density ◽  
Zero Point ◽  
Vacuum Energy Density ◽  
Zero Point Energy ◽  
Observable Universe ◽  
Point Energy

AbstractAn attempt is made to explain dark energy and dark matter of the expanding universe in terms of the zero point vacuum energy. This analysis is mainly limited to later stages of an observable nearly flat universe. It is based on a revised formulation of the spectral distribution of the zero point energy, for an ensemble in a defined statistical equilibrium having finite total energy density. The steady and dynamic states are studied for a spherical cloud of zero point energy photons. The ‘antigravitational’ force due to its pressure gradient then represents dark energy, and its gravitational force due to the energy density represents dark matter. Four fundamental results come out of the theory. First, the lack of emitted radiation becomes reconcilable with the concepts of dark energy and dark matter. Second, the crucial coincidence problem of equal orders of magnitude of mass density and vacuum energy density cannot be explained by the cosmological constant, but is resolved by the present variable concepts, which originate from the same photon gas balance. Third, the present approach becomes reconcilable with cosmical dimensions and with the radius of the observable universe. Fourth, the deduced acceleration of the expansion agrees with the observed one. In addition, mass polarity of a generalized gravitation law for matter and antimatter is proposed as a source of dark flow.

scholarly journals A Solution of the Cosmological Constant and DE and Arrow of Time, Using Model of a Nonsingular Universe from Rosen from Volume (56) Ettore Majorana International Science Series, Physics, 1991

2021 ◽  
Author(s):  
Andrew W. Beckwith
Keyword(s):  
Initial Conditions ◽  
Zero Point ◽  
Cosmic Acceleration ◽  
Energy Calculation ◽  
Arrow Of Time ◽  
Point Energy ◽  
Ettore Majorana ◽  
A Value ◽  
Starting Point ◽  
The Given

We reduplicate the Book “Dark Energy” by M. Li, X-D. Li, and Y. Wang, given zero-point energy calculation with an unexpected “length’ added to the ‘width’ of a graviton wave just prior to specifying the creation of ‘gravitons’, using the Rosen and Israelit model of a nonsingular universe. In doing so we are in addition to obtaining a wavelength 10^30 times greater than Planck’s length so we can calculate DE, may be able to with the help of the Rosen and Israelit model have a first approximation as to the arrow of time, and a universe with massive gravity. We have left the particulars of the nonsingular starting point undefined but state that the Rosen and Israelit model postulates initial temperatures of 10^-180 Kelvin and also a value of about Planck temperature, at 10^-3 centimeters radii value which may satisfy initial conditions asked by t’Hooft for describing an arrow of time. A key assumption is that the DE is formed at 10^-3 cm, after an expansion of 10^30 times in radii, from the Planck length radius nonsingular starting point. The given starting point for DE in this set of assumptions is where there is a change in the cosmic acceleration, to a zero value, according to Rosen and Israel, with time t = 1.31 times 10^-42 seconds. Which may be where we may specify a potential magnitude, V, which has ties into inflaton physics. The particulars of the model from Rosen and Israelit allow a solution to be found, without discussion of where that nonsingular starting point came from, a point the author found in need of drastic remedies and fixes.

Quantum fields and gravity: Expanding space-times

2020 ◽  
Vol 35 (02n03) ◽  
pp. 2040039
Author(s):  
Claudio Parmeggiani
Keyword(s):  
Energy Density ◽  
Vacuum Energy ◽  
Fock Space ◽  
Zero Point ◽  
Big Bang ◽  
Space Time ◽  
Vacuum Energy Density ◽  
Dimensional Manifold ◽  
Quantum Fields ◽  
Point Energy

We discuss a proposal for a somewhat new formulation of quantum field theory (set in a four-dimensional manifold, the space-time) that includes an analysis of its implications for the evolution of Einstein-Friedmann cosmological models. The proposed theory displays two peculiar features: (i) a local Hilbert-Fock space is associated with each space-time point: we are dealing with a vector bundle whose fibers are Hilbert spaces; the operator-valued sections of the bundle are the quantum fields; (ii) the vacuum energy density is finite, being regularized in a space-time curvature dependent way, independently at each point. In fact everything is finite: self-masses, self-charges, quantum fluctuations: they depend on the space-time curvature and diverge only for a flat metric. In an Einstein-Friedmann model the vacuum (zero-point) energy density is consequently time-dependent and in general not negligible. Then it is shown that, for some choices of the parameters of the theory, the big-bang singularity is resolved and replaced by a bounce driven by the vacuum energy density, which becomes (very) large and negative near the bounce (negative by the contribution of the Fermi fields). But for large times (now, say) the Bose fields’ positive vacuum energy eventually overcomes the negative one and we are finally left with the present vacuum energy: positive and reasonably small.

scholarly journals ZERO-POINT ENERGY OF MASSLESS SCALAR FIELDS IN THE PRESENCE OF SOFT AND SEMIHARD BOUNDARIES IN D DIMENSIONS

1999 ◽  
Vol 14 (13) ◽  
pp. 2077-2089 ◽  
Author(s):  
F. CARUSO ◽  
R. DE PAOLA ◽  
N. F. SVAITER
Keyword(s):  
Scalar Field ◽  
Energy Density ◽  
Zero Point ◽  
Scalar Fields ◽  
Flat Space ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Zero Point Energy ◽  
Point Energy ◽  
Renormalized Energy

The renormalized energy density of a massless scalar field defined in a D-dimensional flat space–time is computed in the presence of "soft" and "semihard" boundaries, modeled by some smoothly increasing potential functions. The sign of the renormalized energy densities for these different confining situations is investigated. The dependence of this energy on D for the cases of "hard" and "soft/semihard" boundaries are compared.

REPULSIVE CASIMIR AND VAN DER WAALS FORCES: FROM MEASUREMENTS TO FUTURE TECHNOLOGIES

2010 ◽  
Vol 25 (11) ◽  
pp. 2252-2259 ◽  
Author(s):  
J. N. MUNDAY ◽  
FEDERICO CAPASSO
Keyword(s):  
Energy Density ◽  
Boundary Conditions ◽  
Electromagnetic Fields ◽  
Experimental Verification ◽  
Zero Point ◽  
Static Friction ◽  
Material Interfaces ◽  
Point Energy ◽  
New Class ◽  
Future Technologies

By engineering the boundary conditions of electromagnetic fields between material interfaces, one can dramatically change the Casimir-Lifshitz force between surfaces as a result of the modified zero-point energy density of the system. Repulsive interactions between macroscopic bodies occur when their dielectric responses obey a particular inequality, as pointed out by Dzyaloshinskii, Lifshitz, and Pitaevskii. We discuss experimental verification of this behavior as well as a description of how this can be used to develop a scheme for quantum levitation. Based on these concepts, we discuss the possible development of a new class of devices based on ultra-low static friction and the ability to sort objects based on their dielectric functions.

On the Use of Quantum Thermal Bath in Unimolecular Fragmentation Simulations

2019 ◽  
Author(s):  
Riccardo Spezia ◽  
Hichem Dammak
Keyword(s):  
Degrees Of Freedom ◽  
Molecular Simulations ◽  
Zero Point ◽  
Thermal Bath ◽  
Unimolecular Dissociation ◽  
Point Energy ◽  
Rotational Degrees Of Freedom ◽  
The Difference ◽  
Nuclear Effects

<div> <div> <div> <p>In the present work we have investigated the possibility of using the Quantum Thermal Bath (QTB) method in molecular simulations of unimolecular dissociation processes. Notably, QTB is aimed in introducing quantum nuclear effects with a com- putational time which is basically the same as in newtonian simulations. At this end we have considered the model fragmentation of CH4 for which an analytical function is present in the literature. Moreover, based on the same model a microcanonical algorithm which monitor zero-point energy of products, and eventually modifies tra- jectories, was recently proposed. We have thus compared classical and quantum rate constant with these different models. QTB seems to correctly reproduce some quantum features, in particular the difference between classical and quantum activation energies, making it a promising method to study unimolecular fragmentation of much complex systems with molecular simulations. The role of QTB thermostat on rotational degrees of freedom is also analyzed and discussed. </p> </div> </div> </div>

scholarly journals Modulation of optical absorption in m-Fe1−xRuxS2 and exploring stability in new m-RuS2

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
H. Joshi ◽  
M. Ram ◽  
N. Limbu ◽  
D. P. Rai ◽  
B. Thapa ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Phonon Dispersion ◽  
Applied Pressure ◽  
Orthorhombic Phase ◽  
Zero Point ◽  
Computational Method ◽  
Crystal Field Theory ◽  
Point Energy ◽  
Practical Applications ◽  
New Phase

AbstractA first-principle computational method has been used to investigate the effects of Ru dopants on the electronic and optical absorption properties of marcasite FeS2. In addition, we have also revealed a new marcasite phase in RuS2, unlike most studied pyrite structures. The new phase has fulfilled all the necessary criteria of structural stability and its practical existence. The transition pressure of 8 GPa drives the structural change from pyrite to orthorhombic phase in RuS2. From the thermodynamical calculation, we have reported the stability of new-phase under various ranges of applied pressure and temperature. Further, from the results of phonon dispersion calculated at Zero Point Energy, pyrite structure exhibits ground state stability and the marcasite phase has all modes of frequencies positive. The newly proposed phase is a semiconductor with a band gap comparable to its pyrite counterpart but vary in optical absorption by around 106 cm−1. The various Ru doped structures have also shown similar optical absorption spectra in the same order of magnitude. We have used crystal field theory to explain high optical absorption which is due to the involvement of different electronic states in formation of electronic and optical band gaps. Lӧwdin charge analysis is used over the customarily Mulliken charges to predict 89% of covalence in the compound. Our results indicate the importance of new phase to enhance the efficiency of photovoltaic materials for practical applications.

scholarly journals Dynamical strengthening of covalent and non-covalent molecular interactions by nuclear quantum effects at finite temperature

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Huziel E. Sauceda ◽  
Valentin Vassilev-Galindo ◽  
Stefan Chmiela ◽  
Klaus-Robert Müller ◽  
Alexandre Tkatchenko
Keyword(s):  
Finite Temperature ◽  
Electrostatic Interactions ◽  
Zero Point ◽  
Quantum Effects ◽  
Van Der Waals Interactions ◽  
Interatomic Distances ◽  
Point Energy ◽  
Molecular Bond ◽  
Energy Surfaces ◽  
Nuclear Quantum Effects

AbstractNuclear quantum effects (NQE) tend to generate delocalized molecular dynamics due to the inclusion of the zero point energy and its coupling with the anharmonicities in interatomic interactions. Here, we present evidence that NQE often enhance electronic interactions and, in turn, can result in dynamical molecular stabilization at finite temperature. The underlying physical mechanism promoted by NQE depends on the particular interaction under consideration. First, the effective reduction of interatomic distances between functional groups within a molecule can enhance the n → π* interaction by increasing the overlap between molecular orbitals or by strengthening electrostatic interactions between neighboring charge densities. Second, NQE can localize methyl rotors by temporarily changing molecular bond orders and leading to the emergence of localized transient rotor states. Third, for noncovalent van der Waals interactions the strengthening comes from the increase of the polarizability given the expanded average interatomic distances induced by NQE. The implications of these boosted interactions include counterintuitive hydroxyl–hydroxyl bonding, hindered methyl rotor dynamics, and molecular stiffening which generates smoother free-energy surfaces. Our findings yield new insights into the versatile role of nuclear quantum fluctuations in molecules and materials.

Sign in / Sign up

Export Citation Format

Share Document