scholarly journals On the destruction of ion-sound waves in plasma with strong space-time dispersion

2012 ◽  
Vol 23 (6) ◽  
pp. 989-1011
Author(s):  
M. O. Korpusov
Keyword(s):  
Space Time ◽  
Sound Waves ◽  
Time Dispersion

scholarly journals Space-time dispersion of graphene conductivity

2007 ◽  
Vol 56 (4) ◽  
pp. 281-284 ◽  
Author(s):  
L. A. Falkovsky ◽  
A. A. Varlamov
Keyword(s):  
Space Time ◽  
Time Dispersion

A Linear Acoustic Phased Array for Nonreciprocal Transmission and Reception

2020 ◽  
Author(s):  
R. Adlakha ◽  
M. Moghaddaszadeh ◽  
M. A. Attarzadeh ◽  
A. Aref ◽  
M. Nouh
Keyword(s):  
Phase Modulation ◽  
Frequency Conversion ◽  
Phased Array ◽  
Space Time ◽  
Mathematical Framework ◽  
Sound Waves ◽  
Asymmetric Transmission ◽  
Time Modulation ◽  
Dynamic Phase ◽  
Phase Angles

Abstract Acoustic phased arrays are capable of steering and focusing a beam of sound via selective coordination of the spatial distribution of phase angles between multiple sound emitters. Here, we propose a controllable acoustic phased array with space-time modulation that breaks time-reversal symmetry, and enables phononic transition in both momentum and energy spaces. By leveraging the dynamic phase modulation, the proposed linear phased array is no longer bound by the reciprocity principle, and supports asymmetric transmission and reception patterns that can be tuned independently. Through theoretical and numerical investigations, we develop and verify a mathematical framework to characterize the nonreciprocal phenomena, and analyze the frequency conversion between the wave fields. The space-time acoustic phased array facilitates unprecedented control over sound waves in a variety of applications including underwater telecommunication.

On the collision of impulsive gravitational waves when coupled with fluid motions

1985 ◽  
Vol 402 (1822) ◽  
pp. 37-65 ◽  
Keyword(s):  
Exact Solution ◽  
Gravitational Waves ◽  
Massive Particle ◽  
Natural Generalization ◽  
Space Time ◽  
Direct Result ◽  
Sound Waves ◽  
Time Singularity ◽  
Consistent Extension ◽  
Ultimate Result

An exact solution of Einstein’s equations, with a source derived from a perfect fluid in which the energy density, ε , is equal to the pressure, p , is obtained. The solution describes the space–time following the collision of plane impulsive gravitational waves and is the natural generalization of the Nutku─Halil solution of the vacuum equations, in the region of interaction under similar basic conditions. A consistent extension of the solution, prior to the instant of collision, requires that the fluid in the region of interaction is the direct result of a transformation of incident null-dust (i. e. of massless particles describing null trajectories). The ultimate result of the collision is the development of a space─time singularity, the nature of which is strongly dependent on the amplitude and the character of the sound waves that are present. The distribution of ε that follows the collision has many intriguing features. The solution obtained in this paper provides the first example of an induced transformation of a massless into a massive particle.

scholarly journals Geodesics of Sound Waves and Their Wave Fronts in Curved Space-Time

1990 ◽  
Vol 84 (5) ◽  
pp. 875-891 ◽  
Author(s):  
M. Takahashi ◽  
T. Ishizuka ◽  
M. Yokosawa
Keyword(s):  
Space Time ◽  
Sound Waves ◽  
Wave Fronts ◽  
Curved Space

scholarly journals Detecting space–time agglomeration processes over the Great Recession using firm-level micro-geographic data

2020 ◽  
Vol 22 (4) ◽  
pp. 419-445
Author(s):  
Giulio Cainelli ◽  
Roberto Ganau ◽  
Yuting Jiang
Keyword(s):  
Great Recession ◽  
Manufacturing Industry ◽  
Space Time ◽  
Firm Level ◽  
Geographic Concentration ◽  
The Great Recession ◽  
Time Dispersion ◽  
Manufacturing Sectors ◽  
Spatio Temporal ◽  
Short Time

Abstract We analyze the spatio-temporal agglomeration dynamics that occurred in the Italian manufacturing industry during the recent period of the Great Recession. To study this phenomenon, we employ three different statistical methods—namely, Ellison and Glaeser’s index of industrial geographic concentration, the spatial K-function, and the space–time K-function—, and rely on a large sample of geo-referenced, single-plant manufacturing firms observed over the period 2007–2012. First, we demonstrate that different statistical techniques can lead to (very) different results. Second, we find that most Italian manufacturing sectors experienced spatial dispersion processes during the period of the Great Recession. Finally, we show that space–time dispersion processes occurred at small spatial distances and short time horizon, although we do not detect statistically significant space–time interactions.

scholarly journals Frequency selective wave beaming in nonreciprocal acoustic phased arrays

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Revant Adlakha ◽  
Mohammadreza Moghaddaszadeh ◽  
Mohammad A. Attarzadeh ◽  
Amjad Aref ◽  
Mostafa Nouh
Keyword(s):  
Frequency Conversion ◽  
Phased Array ◽  
Phased Arrays ◽  
Space Time ◽  
Sound Waves ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Asymmetric Transmission ◽  
Phase Angles ◽  
Non Destructive

AbstractAcoustic phased arrays are capable of steering and focusing a beam of sound via selective coordination of the spatial distribution of phase angles between multiple sound emitters. Constrained by the principle of reciprocity, conventional phased arrays exhibit identical transmission and reception patterns which limit the scope of their operation. This work presents a controllable space–time acoustic phased array which breaks time-reversal symmetry, and enables phononic transition in both momentum and energy spaces. By leveraging a dynamic phase modulation, the proposed linear phased array is no longer bound by the acoustic reciprocity, and supports asymmetric transmission and reception patterns that can be tuned independently at multiple channels. A foundational framework is developed to characterize and interpret the emergent nonreciprocal phenomena and is later validated against benchmark numerical experiments. The new phased array selectively alters the directional and frequency content of the incident signal and imparts a frequency conversion between different wave fields, which is further analyzed as a function of the imposed modulation. The space–time acoustic phased array enables unprecedented control over sound waves in a variety of applications ranging from ultrasonic imaging to non-destructive testing and underwater SONAR telecommunication.

Uniform asymptotics for spherical and cylindrical nonlinear acoustic waves generated by a sinusoidal source

1981 ◽  
Vol 375 (1761) ◽  
pp. 211-230 ◽  
Keyword(s):  
Acoustic Waves ◽  
Space Time ◽  
Nonlinear Propagation ◽  
Sound Waves ◽  
Acoustic Beam ◽  
Order Unity ◽  
Spherical Waves ◽  
Leading Term ◽  
Nonlinear Acoustic ◽  
Time Away

This paper is concerned with the nonlinear propagation of sound waves from spherical or cylindrical sinusoidal sources. This problem is governed by the two dimensionless parameters ε and R 0 , and we seek asymptotic expansions valid uniformly in ε , R 0 (as well as in space-time) away from the irreducible domain where both ε and R 0 are of order unity. Various matching asymptotic domains of the parameter plane are defined and in each domain the space-time asymptotic structure is given: in many cases the leading term can actually be solved for analytically. Finally, the application of the results for spherical waves to the important problem of nonlinear acoustic beam spreading are discussed.

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