Abstract. Consider a Kirchhoff plate ∂2 t u+Δ 2u−∂2 t Δu = 0 in Ω× (0, T ), with boundary data u = Δu = 0 on ∂Ω×(0, T ) and unknown initial data u(·, 0) = u0 and ∂tu(·, 0) = u1 in Ω. We study an inverse problem of determining (u0, u1) from an interior observation u|ω×(0,T ). Here Ω is a bounded domain, ω a nonempty open subset of Ω, and T > 0 a suitable time duration. By means of an iterative t...

Rohrlich’s recent claim that the equation of motion for a point charge be symmetric under time reversal is shown to be the result of an unusual definition. The equation of motion for a charged sphere of finite size, which in contrast is claimed to be asymmetric because of the finite propagation time of its (retarded) self-forces, is shown to possess the same asymmetry (or the same symmetry, dep...

This paper illustrates that the application of the time reversal technique in multiple inputsingle output (MISO) communications systems can effectively limit the perceived delay spread of the channel. Fixed wireless access channels in the 5GHz band have been measured with 8 element uniform linear antenna arrays at both ends, thus providing an 8x8 MIMO configuration. The measurements were perfor...

We present an analysis of short-time time-reversal on audio signals. Based on our analysis, we define parameters that can be used to control the digital effect and explain the effect each parameter has on the output. We further study the case of 50% overlap-add, then use this for a real-time implementation. Depending on the window length, the effect can modify the output sound variously, from a...

A prior study of short-time time-reversal showed sideband modulation occurs for short time durations, creating overtones for single sinusoid signals. In this paper, we examine the overtones created by short-time time-reversal and the tonal relation between the overtones and the input signal. We present three methods of using short-time time-reversal for harmonizing audio signals. Then modificat...

When a signal is emitted from a source, recorded by an array of transducers, time reversed and re-emitted into the medium, it will refocus approximately on the source location. We analyze the refocusing resolution in a high frequency, remote sensing regime, and show that, because of multiple scattering, in an inhomogeneous or random medium it can improve beyond the diffraction limit. We also sh...

Many electrical and mechanical systems with two normal modes are appropriate for illustrating the quantum mechanics of neutral kaons. The illustration of CPor time-reversal-violation in the neutral kaon system by mechanical or electrical analogues is more subtle. Some possibilities which could be realized in a table-top demonstration are suggested.

Richard Feynman has claimed that anti-particles are nothing but particles ‘propagating backwards in time’; that time reversing a particle state always turns it into the corresponding anti-particle state. According to standard quantum field theory textbooks this is not so: time reversal does not turn particles into anti-particles. Feynman’s view is interesting because, in particular, it suggests...

During November 1994, broadband acoustic signals were transmitted from a 75-Hz source to a 20-element, 700-m vertical array at approximately 3250 km range in the eastern North Pacific Ocean as part of the acoustic engineering test (AET) of the acoustic thermometry of ocean climate program [Worcester et al., J. Acoust. Soc. Am. 105, 3185-3201 (1999)]. The AET tomography signal can be treated as ...

Time reversal invariance can be summarised as follows: no difference can be measured if a sequence of events is run forward or backward in time. Because price time series are dominated by a randomness that hides possible structures and orders, the existence of time reversal invariance requires care to be investigated. Different statistics are constructed with the property to be zero for time se...