scholarly journals Casimir Puzzle and Casimir Conundrum: Discovery and Search for Resolution

Universe ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 84
Author(s):  
Vladimir M. Mostepanenko
Keyword(s):  
Measurement Data ◽  
Perfect Crystal ◽  
Casimir Forces ◽  
Alternative Response ◽  
Crystal Lattices ◽  
Conduction Electrons ◽  
Real Material ◽  
Lifshitz Theory ◽  
Experimental Findings ◽  
Theoretical Results

This paper provides a review of the complicated problems in Lifshitz theory describing the Casimir force between real material plates composed of metals and dielectrics, including different approaches to their resolution. For both metallic plates with perfect crystal lattices and any dielectric plates, we show that the Casimir entropy calculated in the framework of Lifshitz theory violates the Nernst heat theorem when the well-approved dielectric functions are used in computations. The respective theoretical Casimir forces are excluded by the measurement data of numerous precision experiments. In the literature, this situation has been called the Casimir puzzle and the Casimir conundrum for the cases of metallic and dielectric plates, respectively. This review presents a summary of both the main theoretical and experimental findings on this subject. Next, a discussion is provided of the main approaches proposed in the literature to bring the Lifshitz theory into agreement with the measurement data and with the laws of thermodynamics. Special attention is paid to the recently suggested spatially nonlocal Drude-like response functions, which consider the relaxation properties of conduction electrons, as does the standard Drude model, but lead to the theoretical results being in agreement with both thermodynamics and the measurement data through the alternative response to quantum fluctuations of the mass shell. Further advances and trends in this field of research are discussed.

scholarly journals An alternative response to the off-shell quantum fluctuations: a step forward in resolution of the Casimir puzzle

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
G. L. Klimchitskaya ◽  
V. M. Mostepanenko
Keyword(s):  
Electromagnetic Waves ◽  
Measurement Data ◽  
Response Functions ◽  
Local Response ◽  
Free Electrons ◽  
Alternative Response ◽  
Local Responses ◽  
Lifshitz Theory ◽  
Principle Of Causality ◽  
Zero Frequency

AbstractThe spatially nonlocal response functions are proposed which nearly coincide with the commonly used local response for electromagnetic fields and fluctuations on the mass shell, but differ significantly for the off-shell fluctuating field. It is shown that the fundamental Lifshitz theory using the suggested response functions comes to an agreement with the measurement data for the Casimir force without neglecting the dissipation of free electrons. We demonstrate that reflectances of the on-shell electromagnetic waves calculated using the nonlocal and commonly employed local responses differ only slightly. The Kramers–Kronig relations for nonlocal response functions possessing the first- and second-order poles at zero frequency are derived, i.e., the proposed response satisfies the principle of causality. An application of these results to resolution of the Casimir puzzle, which lies in the fact that the Lifshitz theory is experimentally consistent only with discarded dissipation, is discussed.

scholarly journals Symmetry/Asymmetry of the NHN Hydrogen Bond in Protonated 1,8-Bis(dimethylamino)naphthalene

Symmetry ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 1924
Author(s):  
Patrycja Piękoś ◽  
Aneta Jezierska ◽  
Jarosław J. Panek ◽  
Eugene A. Goremychkin ◽  
Alexander F. Pozharskii ◽  
...  
Keyword(s):  
Density Functional ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Functional Theory ◽  
Protonated Forms ◽  
Motional Dynamics ◽  
Proton Dynamics ◽  
Experimental Findings ◽  
Bridge Vibrations ◽  
Theoretical Results

Experimental and theoretical results are presented based on vibrational spectra and motional dynamics of 1,8-bis(dimethylamino)naphthalene (DMAN) and its protonated forms (DMANH+ and the DMANH+ HSO4− complex). The studies of these compounds have been performed in the gas phase and solid-state. Spectroscopic investigations were carried out by infrared spectroscopy (IR), Raman, and incoherent inelastic neutron scattering (IINS) experimental methods. Density functional theory (DFT) and Car–Parrinello molecular dynamics (CPMD) methods were applied to support our experimental findings. The fundamental investigations of hydrogen bridge vibrations were accomplished on the basis of isotopic substitutions (NH → ND). Special attention was paid to the bridged proton dynamics in the DMANH+ complex, which was found to be affected by interactions with the HSO4− anion.

Systematic first principles calculations of the effects of stacking faults defects on the 4H-SiC band structure

2010 ◽  
Vol 1246 ◽  
Author(s):  
Massimo Camarda ◽  
pietro delugas ◽  
Andrea Canino ◽  
Andrea Severino ◽  
nicolo piluso ◽  
...  
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Stacking Faults ◽  
Perfect Crystal ◽  
First Principles Calculations ◽  
Electronic Band ◽  
Functional Theory ◽  
Experimental Findings ◽  
Electronic Band Structures ◽  
Formation Energies

AbstractShockley-type Stacking faults (SSF) in hexagonal Silicon Carbide polytypes have received considerable attention in recent years since it has been found that these defects are responsible for the degradation of forward I-V characteristics in p-i-n diodes. In order to extend the knowledge on these kind of defects and theoretically support experimental findings (specifically, photoluminescence spectral analysis), we have determined the Kohn-Sham electronic band structures, along the closed path Γ-M-K-Γ, using density functional theory. We have also determined the energies of the SSFs with respect to the perfect crystal finding that the (35) and (44) SSFs have unexpectedly low formation energies, for this reason we could expect these two defects to be easily generated/expanded either during the growth or post-growth process steps.

scholarly journals X-ray gain at 18·2 nm (CVI Balmer α) in laser-produced recombining carbon plasmas

1988 ◽  
Vol 6 (3) ◽  
pp. 621-624 ◽  
Author(s):  
W. Brunner ◽  
R. John ◽  
Th. Schlegel
Keyword(s):  
Plasma Heating ◽  
Laser Pulses ◽  
X Ray ◽  
Short Laser Pulses ◽  
Experimental Findings ◽  
Theoretical Results

Plasma heating by short laser pulses is investigated theoretically. Gain coefficients of 3… 4 cm−1 at the Balmer α transition in carbon could be obtained. The theoretical results agree with the corresponding experimental findings.

scholarly journals Selected aspects of a cold forging process for hollow balls

2021 ◽  
Author(s):  
Grzegorz Samołyk ◽  
Grzegorz Winiarski
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
Wall Thickness ◽  
Experimental Testing ◽  
Wide Spectrum ◽  
Cold Forging ◽  
Hole Size ◽  
Forging Process ◽  
Experimental Findings ◽  
Theoretical Results

AbstractThis paper presents the results of a study investigating a cold forging process for producing hollow balls with different wall thicknesses. The study was performed by FEM numerical modelling, which made it possible to obtain a wide spectrum of results. For the analysis of FEM results obtained for problematic cases (shape defects in forged balls), novel hypotheses for results interpretation are proposed. The FEM numerical model and hypotheses are then verified via experimental testing, and selected theoretical results are compared with experimental findings. Finally, obtained results are discussed (e.g. the effect of billet dimensions on forging conditions, wall thickness and hole size), a method for FEM results interpretation is presented, and design-related solutions ensuring the production of defect-free hollow balls are proposed.

scholarly journals RECENT RESULTS ON THERMAL CASIMIR FORCE BETWEEN DIELECTRICS AND RELATED PROBLEMS

2006 ◽  
Vol 21 (25) ◽  
pp. 5007-5042 ◽  
Author(s):  
B. GEYER ◽  
G. L. KLIMCHITSKAYA ◽  
V. M. MOSTEPANENKO
Keyword(s):  
Free Energy ◽  
Low Temperature ◽  
Dielectric Permittivity ◽  
Casimir Force ◽  
Dc Conductivity ◽  
Charge Carrier Density ◽  
Casimir Forces ◽  
Dielectric Plate ◽  
Static Dielectric Permittivity ◽  
Lifshitz Theory

We review recent results obtained in the physics of the thermal Casimir force acting between two dielectrics, dielectric and metal, and between metal and semiconductor. The detailed derivation for the low-temperature behavior of the Casimir free energy, pressure and entropy in the configuration of two real dielectric plates is presented. For dielectrics with finite static dielectric permittivity it is shown that the Nernst heat theorem is satisfied. Hence, the Lifshitz theory of the van der Waals and Casimir forces is demonstrated to be consistent with thermodynamics. The nonzero dc conductivity of dielectric plates is proved to lead to a violation of the Nernst heat theorem and, thus, is not related to the phenomenon of dispersion forces. The low-temperature asymptotics of the Casimir free energy, pressure and entropy are derived also in the configuration of one metal and one dielectric plate. The results are shown to be consistent with thermodynamics if the dielectric plate possesses a finite static dielectric permittivity. If the dc conductivity of a dielectric plate is taken into account this results in the violation of the Nernst heat theorem. We discuss both the experimental and theoretical results related to the Casimir interaction between metal and semiconductor with different charge carrier density. Discussions in the literature on the possible influence of spatial dispersion on the thermal Casimir force are analyzed. In conclusion, the conventional Lifshitz theory taking into account only the frequency dispersion remains the reliable foundation for the interpretation of all present experiments.

Self-Consistent Supercell Band-Structure Calculations for the Investigation of the Electric Field Gradient at Impurity Sites in Cd Metal

1987 ◽  
Vol 42 (11) ◽  
pp. 1321-1326 ◽  
Author(s):  
P. C. Schmidt ◽  
Al. Weiss ◽  
S. Cabus ◽  
J. Küber
Keyword(s):  
Band Structure ◽  
Electric Field ◽  
Electric Field Gradient ◽  
Field Gradient ◽  
Band Structure Calculations ◽  
Densities Of States ◽  
Experimental Findings ◽  
Impurity Sites ◽  
Structure Calculations ◽  
Theoretical Results

The electric field gradient (EFG) at the nuclei of the 5 sp impurities In, Sn, Sb, I and Xe in Cd metal is investigated on the basis of supercell band structure calculations of Cd15M(M = In , . . . , Xe). The theoretical results show the same trend as the experimental findings. The differences in the EFG for different impurities are related to the charge distribution and partial densities of states.

SELF-CONSISTENT X-RAY DIFFRACTION PATTERNS OF PERFECT CRYSTAL

1989 ◽  
Vol 03 (16) ◽  
pp. 1221-1224 ◽  
Author(s):  
H. S. CAMPOS ◽  
W. A. KELLER
Keyword(s):  
Perfect Crystal ◽  
X Ray Diffraction ◽  
Reflection Curve ◽  
X Ray ◽  
Scattering Model ◽  
X Ray Scattering ◽  
Self Consistent ◽  
Diffraction Patterns ◽  
Experimental Findings ◽  
Ray Scattering

We have developed a self-consistent X-ray scattering model for perfect crystal, which leads to obtain diffraction patterns similar to experimental findings. As an application of the model we carried out the calculations for the Si[333] reflection curve.

Self-Compression and Diamond Nucleation In Irradiated Carbon Onions - A Theoretical Model

1998 ◽  
Vol 540 ◽  
Author(s):  
M. Zaiser
Keyword(s):  
Theoretical Model ◽  
Diamond Formation ◽  
Diamond Nucleation ◽  
Diamond Crystals ◽  
Carbon Onions ◽  
Experimental Findings ◽  
Theoretical Results ◽  
Good Agreement

AbstractThe nucleation of small diamond crystals during irradiation of spherical graphitic particles (’bucky onions’) is discussed. A mechanism for irradiation-induced self-compression of such ’onions’ is proposed. It is demonstrated that this may yield pressures which are sufficiently high for diamond formation. The theoretical results are in good agreement with experimental findings.

scholarly journals Force Recruitment of Neuromuscular Magnetic Stimulation Predicted Through High-Resolution Anatomical 3D Models

2021 ◽  
Author(s):  
Stefan M Goetz ◽  
Joerg Kammermann ◽  
Florian Helling ◽  
Thomas Weyh ◽  
Zhongxi Li
Keyword(s):  
Experimental Data ◽  
Magnetic Stimulation ◽  
Dynamic Models ◽  
Measurement Data ◽  
Coupled Model ◽  
3D Models ◽  
Promising Tool ◽  
Wide Range ◽  
Experimental Findings ◽  
Recruitment Model

Neuromuscular magnetic stimulation is a promising tool in neurorehabilitation due to its deeper penetration, notably lower distress, and respectable force levels compared to electrical stimulation. However, this method faces great challenges from a technological perspective. The systematic design of better equipment and the incorporation into modern training setups requires better understanding of the mechanisms and predictive quantitative models of the recruited forces. This article proposes a model for simulating the force recruitment in isometric muscle stimulation of the thigh extensors based on previous theoretical and experimental findings. The model couples a 3D field model for the physics with a parametric recruitment model, which is identified with a mixed-effects design to learn the most likely model based on available experimental data with a wide range of field conditions. This approach intentionally keeps the model as mathematically simple and statistically parsimonious as possible in order to avoid over-fitting. The coupled model is able to accurately predict key phenomena observed so far, such as a threshold shift for different distances between coil and body, the different recruiting performance of various coils with available measurement data in the literature, and the saturation behaviour with its onset amplitude. The presented recruitment model could also be readily incorporated into dynamic models for biomechanics as soon as sufficient experimental data are available for calibration.

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