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 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.

Experimental Study for Extraction of Normal Modes

1995 ◽  
Author(s):  
S. Y. Chen ◽  
M. S. Ju ◽  
Y. G. Tsuei
Keyword(s):  
Frequency Response ◽  
Normal Mode ◽  
Normal Modes ◽  
Measurement Data ◽  
Mode Shapes ◽  
Complex Frequency ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Incomplete System ◽  
Coupled Structures

Abstract A frequency-domain technique to extract the normal mode from the measurement data for highly coupled structures is developed. The relation between the complex frequency response functions and the normal frequency response functions is derived. An algorithm is developed to calculate the normal modes from the complex frequency response functions. In this algorithm, only the magnitude and phase data at the undamped natural frequencies are utilized to extract the normal mode shapes. In addition, the developed technique is independent of the damping types. It is only dependent on the model of analysis. Two experimental examples are employed to illustrate the applicability of the technique. The effects due to different measurement locations are addressed. The results indicate that this technique can successfully extract the normal modes from the noisy frequency response functions of a highly coupled incomplete system.

Practical Considerations for Waveguide-Ballistic Thermal Energy Conversion

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Michael Wieckowski ◽  
Martin Margala
Keyword(s):  
Finite Element Method ◽  
High Frequency ◽  
Electromagnetic Waves ◽  
Finite Element Method Simulation ◽  
Electrical Energy ◽  
Heat Energy ◽  
Free Electrons ◽  
Thermal Energy Conversion ◽  
Metal Waveguide ◽  
Dc Potential

The potential of converting heat energy into electrical energy using a previously reported waveguide-ballistic device is presented. The interactions between incident electromagnetic waves and free electrons in a metal waveguide are analyzed with respect to their transport through a high-frequency ballistic rectifier using finite element method simulation. It was determined that the resulting conversion efficiency to a dc potential is approximately 6%, yielding a power density on the order of 30W∕m2.

Dielectric Response of β-HMX at THz Frequencies Calculated by Density Functional Theory

2011 ◽  
Author(s):  
Lulu Huang ◽  
Andrew Shabaev ◽  
Samuel G. Lambrakos ◽  
Noam Bernstein ◽  
Verne L. Jacobs ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Ground State ◽  
Dielectric Response ◽  
Electromagnetic Waves ◽  
Density Functional ◽  
Spectral Response ◽  
Resonance Structure ◽  
Response Functions ◽  
Functional Theory ◽  
State Resonance

We present calculations of ground state resonance structure associated with the high explosives β-HMX using density functional theory (DFT), which is for the construction of parameterized dielectric response functions for excitation by electromagnetic waves at compatible frequencies. These dielectric functions provide for different types of analyses concerning the dielectric response of explosives. In particular, these dielectric response functions provide quantitative initial estimates of spectral response features for subsequent adjustment with respect to additional information such as laboratory measurements and other types of theory based calculations. With respect to qualitative analysis, these spectra provide for the molecular level interpretation of response structure. The DFT software GAUSSIAN was used for the calculations of ground state resonance structure presented here.

scholarly journals Bias Errors due to Leakage Effects When Estimating Frequency Response Functions

2012 ◽  
Vol 19 (6) ◽  
pp. 1257-1266 ◽  
Author(s):  
Andreas Josefsson ◽  
Kjell Ahlin ◽  
Göran Broman
Keyword(s):  
Frequency Response ◽  
Measurement Data ◽  
Approximate Expression ◽  
Bias Error ◽  
Systematic Bias ◽  
Response Functions ◽  
Random Errors ◽  
Frequency Response Functions ◽  
Rectangular Window ◽  
Wide Range

Frequency response functions are often utilized to characterize a system's dynamic response. For a wide range of engineering applications, it is desirable to determine frequency response functions for a system under stochastic excitation. In practice, the measurement data is contaminated by noise and some form of averaging is needed in order to obtain a consistent estimator. With Welch's method, the discrete Fourier transform is used and the data is segmented into smaller blocks so that averaging can be performed when estimating the spectrum. However, this segmentation introduces leakage effects. As a result, the estimated frequency response function suffers from both systematic (bias) and random errors due to leakage. In this paper the bias error in theH1andH2-estimate is studied and a new method is proposed to derive an approximate expression for the relative bias error at the resonance frequency with different window functions. The method is based on using a sum of real exponentials to describe the window's deterministic autocorrelation function. Simple expressions are derived for a rectangular window and a Hanning window. The theoretical expressions are verified with numerical simulations and a very good agreement is found between the results from the proposed bias expressions and the empirical results.

scholarly journals Subwavelength Plasmonic Waveguides and Plasmonic Materials

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
Ruoxi Yang ◽  
Zhaolin Lu
Keyword(s):  
Electromagnetic Waves ◽  
High Speed ◽  
Negative Permittivity ◽  
Plasmonic Waveguides ◽  
Free Electrons ◽  
Plasmonic Materials ◽  
Fast Development ◽  
High Speed Data ◽  
Microfabrication Technology ◽  
Plasmon Polaritons

With the fast development of microfabrication technology and advanced computational tools, nanophotonics has been widely studied for high-speed data transmission, sensitive optical detection, manipulation of ultrasmall objects, and visualization of nanoscale patterns. As an important branch of nanophotonics, plasmonics has enabled light-matter interactions at a deep subwavelength length scale. Plasmonics, or surface plasmon based photonics, focus on how to exploit the optical property of metals with abundant free electrons and hence negative permittivity. The oscillation of free electrons, when properly driven by electromagnetic waves, would form plasmon-polaritons in the vicinity of metal surfaces and potentially result in extreme light confinement. The objective of this article is to review the progress of subwavelength or deep subwavelength plasmonic waveguides, and fabrication techniques of plasmonic materials.

Damage Detection of Shear Connectors Based on Power Spectral Density Transmissibility

2013 ◽  
Vol 569-570 ◽  
pp. 1241-1248 ◽  
Author(s):  
Jun Li ◽  
Hong Hao
Keyword(s):  
Spectral Density ◽  
Damage Detection ◽  
Frequency Response ◽  
Power Spectral Density ◽  
Experimental Studies ◽  
Measurement Data ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Shear Connectors ◽  
Power Spectral

Damage of shear connectors in slab-on-girder structures will result in shear slippage between slab and girder, which significantly reduces the load-carrying capacity of the bridge. This paper proposes a dynamic damage detection approach to identify the damage of shear connectors in slab-on-girder bridges with power spectral density transmissibility (PSDT). PSDT formulates the relationship between the auto-spectral density functions of two responses. Measured impact force and acceleration responses from hammer tests are analyzed to obtain the frequency response functions at the slab and girder sensor locations by experimental modal analysis. When measurement data from the undamaged structure are available, PSDT from the slab response to the girder response is derived with the obtained frequency response functions. PSDT matrices in the undamaged and damaged states are directly compared to identify the damage of shear connectors. When the measurement data from the undamaged structure are not available, PSDT matrices from measured response at a reference sensor response to those of the slab and girder in the damaged state can also be used to detect the damage of shear connectors. Experimental studies with a concrete slab supported by two steel girders are conducted to investigate the accuracy and efficiency of the proposed approach. Identification results demonstrated that damage of shear connectors can be identified accurately and efficiently with and without measurement data from the undamaged structure.

scholarly journals On Antiresonance in the Forced Response of Mistuned Bladed Disks

2003 ◽  
Vol 10 (2) ◽  
pp. 135-146 ◽  
Author(s):  
Keith Jones ◽  
Charles Cross
Keyword(s):  
Natural Frequencies ◽  
Critical Factor ◽  
Forced Response ◽  
Turbine Engines ◽  
Response Functions ◽  
Local Response ◽  
Bladed Disks ◽  
Important Conclusion ◽  
Bladed Disk ◽  
Lower Maximum

Mistuning in bladed disks usually increases the forced response of the maximum responding blade leading to shortened component life in turbine engines. This paper investigates mistuning using a transfer function approach where the frequency response functions (FRFs) are described by natural frequencies and antiresonant frequencies. Using this approach, antiresonant frequencies are shown to be a critical factor in determining the maximum blade response. Two insights are gained by formulating antiresonant frequencies as the eigenvalues of reduced system matrices: 1) Mistuning a particular blade has no effect on that blade's antiresonant frequencies. 2) Engine orders N and N/2, where N is the number of blades on the disk, tend to produce the highest maximum local response. Numerical examples are given using a spring-mass-oscillator model of a bladed disk. Pole-zero loci of mistuned bladed disks show that increased maximum blade response is often due to the damping of antiresonant frequencies. An important conclusion is that antiresonant frequencies can be arranged such that a mistuned bladed disk has a lower maximum blade response than a tuned bladed disk.

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