scholarly journals Parametric broadening of the molecular vibronic band due to zero-point oscillations and thermal fluctuations of interatomic bonds

AIP Advances ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 035115
Author(s):  
Peter Lebedev-Stepanov
Keyword(s):  
Zero Point ◽  
Thermal Fluctuations ◽  
Vibronic Band

Near-Field Radiative Transfer, Dispersion Forces, and Dyadic Green’s Functions

2009 ◽  
Author(s):  
Arvind Narayanaswamy
Keyword(s):  
Radiative Transfer ◽  
Near Field ◽  
Field Enhancement ◽  
Zero Point ◽  
Thermal Fluctuations ◽  
Function Technique ◽  
Dispersion Forces ◽  
Maxwell Stress Tensor ◽  
Open Questions ◽  
Greens Function

Near–field force and energy exchange between two objects due to electrodynamic fluctuations give rise to dispersion forces such as Casimir and van der Waals forces, and thermal radiative transfer exceeding Plancks theory of blackbody radiation. The two phenomena dispersion forces and near–field enhancement of thermal radiation have common origins in the electromagnetic fluctuations. However, dispersion forces have contributions from quantum (zero–point) as well as thermal fluctuations whereas nearfield radiative transfer has contributions from thermal fluctuations alone. The forces are manifested through the Maxwell stress tensor of the electromagnetic field and radiative transfer through the Poynling vector. Both phenomena are elegantly described in terms of the Dyadic Greens function of the vector Helmholtz equation that governs the electromagnetic fields. In this talk, I will focus on the application of the Dyadic Greens function technique to near–field radiative transfer and dispersion forces. Despite the similarities, radiative transfer and forces have important differences that will be stressed on. I will end the talk with some open questions about the Dyadic Greens function formalism and its application to near–field radiative transfer.

scholarly journals The Puzzling of Zero-Point Energy Contribution to Black-Body Radiation Spectrum: The Role of Casimir Force

2017 ◽  
Vol 16 (04) ◽  
pp. 1771002 ◽  
Author(s):  
L. Reggiani ◽  
E. Alfinito
Keyword(s):  
Casimir Force ◽  
Radiation Spectrum ◽  
Mechanical Stability ◽  
Zero Point ◽  
Direct Consequence ◽  
Black Body ◽  
Thermal Fluctuations ◽  
Black Body Radiation ◽  
Point Energy ◽  
Nyquist Noise

The role played by zero-point contribution in black-body radiation spectrum is investigated in connection with the presence of Casimir force. We assert that once mechanical stability for the physical system is established, there is no further role for zero-point contribution to the spectrum in full agreement with experimental evidence. As a direct consequence, Johnson–Nyquist noise in dissipative conductors, should be interpreted just in terms of thermal fluctuations only, thus neglecting quantum fluctuations predicted by [H. Callen and T. Welton, Irreversibility and generalized noise, Phys. Rev. 83 (1951) 34]. Casimir force between opposite metallic plates can be independently measured by its equilibration through application of a mechanical force and measuring it at a mechanical equilibrium.

ZERO—POINT SPIN FLUCTUATION EFFECTS IN ANHARMONIC WEAK ITINERANT ELECTRON MAGNETS

1993 ◽  
Vol 07 (01n03) ◽  
pp. 585-588 ◽  
Author(s):  
ALEXANDER SOLONTSOV
Keyword(s):  
Inelastic Neutron Scattering ◽  
Spin Fluctuation ◽  
Landau Theory ◽  
Zero Point ◽  
Thermal Fluctuations ◽  
Inelastic Neutron ◽  
Spin Fluctuations ◽  
Itinerant Electron ◽  
Fluctuation Effects

The spin fluctuation theory of weak itinerant magnets is critically reviewed and is shown to be well established in the weak spin anharmonicity limit. A new self—consistent approach is formulated in terms of the Landau theory of phase transitions to account for zero—point and thermal fluctuations in anharmonic itinerant magnets. The role of spin fluctuations and Fermi excitations in MnSi, Ni3Al and ZrZn2 is discussed using the inelastic neutron scattering experiments.

Systematic effects in observed parallaxes

1978 ◽  
Vol 48 ◽  
pp. 31-35
Author(s):  
R. B. Hanson
Keyword(s):  
Error Estimates ◽  
Zero Point ◽  
Absolute Zero ◽  
Apparent Magnitude ◽  
Coherent System ◽  
Preliminary Results ◽  
General Catalogue ◽  
Systematic Effects ◽  
New Evidence ◽  
Right Ascension

Several outstanding problems affecting the existing parallaxes should be resolved to form a coherent system for the new General Catalogue proposed by van Altena, as well as to improve luminosity calibrations and other parallax applications. Lutz has reviewed several of these problems, such as: (A) systematic differences between observatories, (B) external error estimates, (C) the absolute zero point, and (D) systematic observational effects (in right ascension, declination, apparent magnitude, etc.). Here we explore the use of cluster and spectroscopic parallaxes, and the distributions of observed parallaxes, to bring new evidence to bear on these classic problems. Several preliminary results have been obtained.

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>

Thermal fluctuations of non-motile magnetotactic bacteria in AC magnetic fields

2008 ◽  
Vol 44 (3) ◽  
pp. 223-236 ◽  
Author(s):  
K. Ērglis ◽  
L. Alberte ◽  
A. Cēbers
Keyword(s):  
Magnetic Fields ◽  
Magnetotactic Bacteria ◽  
Thermal Fluctuations

Casimir forces and vacuum energy

2017 ◽  
Author(s):  
Serge Reynaud ◽  
Astrid Lambrecht
Keyword(s):  
Casimir Force ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Thermal Fluctuations ◽  
Model Systems ◽  
Vacuum Field ◽  
Force Measurements ◽  
Casimir Forces ◽  
Current State ◽  
Field Fluctuations

The Casimir force is an effect of quantum vacuum field fluctuations, with applications in many domains of physics. The ideal expression obtained by Casimir, valid for perfect plane mirrors at zero temperature, has to be modified to take into account the effects of the optical properties of mirrors, thermal fluctuations, and geometry. After a general introduction to the Casimir force and a description of the current state of the art for Casimir force measurements and their comparison with theory, this chapter presents pedagogical treatments of the main features of the theory of Casimir forces for one-dimensional model systems and for mirrors in three-dimensional space.

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