scholarly journals PHASE TIME FOR A TUNNELING PARTICLE

2007 ◽  
Vol 21 (10) ◽  
pp. 1681-1704 ◽  
Author(s):  
SWARNALI BANDOPADHYAY ◽  
A. M. JAYANNAVAR
Keyword(s):  
Time Delays ◽  
Arrival Time ◽  
Quantum Mechanical ◽  
Quantum Networks ◽  
Potential Barriers ◽  
Phase Time ◽  
Hartman Effect ◽  
Aharonov Bohm ◽  
Negative Time ◽  
Two Barriers

We study the nature of tunneling phase time for various quantum mechanical structures such as networks and rings having potential barriers in their arms. We find the generic presence of the Hartman effect, with superluminal velocities as a consequence, in these systems. In quantum networks, it is possible to control the "super arrival" time in one of the arms by changing the parameters on another arm which is spatially separated from it. This is yet another quantum nonlocal effect. Negative time delays (time advancement) and "ultra Hartman effect" with negative saturation times have been observed in some parameter regimes. In the presence and absence of Aharonov-Bohm (AB) flux, quantum rings show the Hartman effect. We obtain the analytical expression for the saturated phase time. In the opaque barrier regime, this is independent of even the AB flux thereby generalizing the Hartman effect. We also briefly discuss the concept of "space collapse or space destroyer" by introducing a free space in between two barriers covering the ring. Further, we show in presence of absorption that the reflection phase time exhibits the Hartman effect in contrast to the transmission phase time.

A Design Method for Modified Smith Predictors for Non-Minimum-Phase Time-Delay Plants with Multiple Feedback-Connected Time-Delays

2010 ◽  
Vol 36 ◽  
pp. 253-262 ◽  
Author(s):  
Iwanori Murakami ◽  
Nghia Thi Mai ◽  
Kou Yamada ◽  
Takaaki Hagiwara ◽  
Yoshinori Ando ◽  
...  
Keyword(s):  
Steady State ◽  
Time Delay ◽  
Time Delays ◽  
Large Time ◽  
Design Method ◽  
Smith Predictor ◽  
Minimum Phase ◽  
Effective Time ◽  
Phase Time ◽  
Step Disturbance

In this paper, we examine a design method for modified Smith predictors for non-minimum-phase time-delay plants with multiple feedback-connected time-delays. The Smith predictor is proposed by Smith to overcome time-delay and known as an effective time-delay compensator for a plant with large time-delay. The Smith predictor by Smith cannot be used for plants having an integral mode, because a step disturbance will result in a steady state error. Several papers considered the problem to design modified Smith predictors for unstable plants. However, no paper examines a design method for modified Smith predictors for non-minimum-phase time-delay plants with multiple feedback-connected time-delays. In this paper, we examine a design method for modified Smith predictors for non-minimum-phase time-delay plants with multiple feedback-connected time-delays.

Quantum mechanical versus quasi-classical tunneling times for smooth potential barriers

2003 ◽  
Vol 81 (3) ◽  
pp. 573-581 ◽  
Author(s):  
M R.A. Shegelski ◽  
E V Kozijn
Keyword(s):  
Quantum Mechanical ◽  
Tunneling Time ◽  
Quantum Mechanical Tunneling ◽  
Potential Barriers ◽  
Smooth Potential ◽  
Tunneling Times

For smooth potential barriers, we compare the quasi-classical tunneling time with an expression that gives a fully quantum mechanical tunneling time. The expression we choose for the quantum mechanical tunneling time is one that has heuristic value. We report results wherein this quantum mechanical tunneling time and the quasi-classical time differ significantly, both quantitatively and qualitatively. To determine the reasons for these differences, we compare the trends in the two times that result from varying the potential. Our findings suggest that, for smooth potential barriers, the quasi-classical tunneling time is unreliable for many cases where it is employed. PACS Nos.: 03.65Xp, 03.65-w

scholarly journals TDCOSMO

2020 ◽  
Vol 642 ◽  
pp. A194 ◽  
Author(s):  
D. Gilman ◽  
S. Birrer ◽  
T. Treu
Keyword(s):  
Dark Matter ◽  
Time Delay ◽  
Time Delays ◽  
Arrival Time ◽  
Cosmological Parameters ◽  
Hubble Constant ◽  
Line Of Sight ◽  
Gravitational Lenses ◽  
Additional Source ◽  
Precision Limit

Time delay cosmography uses the arrival time delays between images in strong gravitational lenses to measure cosmological parameters, in particular the Hubble constant H0. The lens models used in time delay cosmography omit dark matter subhalos and line-of-sight halos because their effects are assumed to be negligible. We explicitly quantify this assumption by analyzing mock lens systems that include full populations of dark matter subhalos and line-of-sight halos, applying the same modeling assumptions used in the literature to infer H0. We base the mock lenses on six quadruply imaged quasars that have delivered measurements of the Hubble constant, and quantify the additional uncertainties and/or bias on a lens-by-lens basis. We show that omitting dark substructure does not bias inferences of H0. However, perturbations from substructure contribute an additional source of random uncertainty in the inferred value of H0 that scales as the square root of the lensing volume divided by the longest time delay. This additional source of uncertainty, for which we provide a fitting function, ranges from 0.7 − 2.4%. It may need to be incorporated in the error budget as the precision of cosmographic inferences from single lenses improves, and it sets a precision limit on inferences from single lenses.

scholarly journals Times of arrival and gauge invariance

2021 ◽  
Vol 477 (2250) ◽  
pp. 20210101
Author(s):  
Siddhant Das ◽  
Markus Nöth
Keyword(s):  
Magnetic Field ◽  
Quantum Mechanics ◽  
Arrival Time ◽  
Free Particle ◽  
Natural Generalization ◽  
Arrival Times ◽  
Quantum Flux ◽  
Freely Moving ◽  
Set Up ◽  
Aharonov Bohm

We revisit the arguments underlying two well-known arrival-time distributions in quantum mechanics, viz., the Aharonov–Bohm–Kijowski (ABK) distribution, applicable for freely moving particles, and the quantum flux (QF) distribution. An inconsistency in the original axiomatic derivation of Kijowski’s result is pointed out, along with an inescapable consequence of the ‘negative arrival times’ inherent to this proposal (and generalizations thereof). The ABK free-particle restriction is lifted in a discussion of an explicit arrival-time set-up featuring a charged particle moving in a constant magnetic field. A natural generalization of the ABK distribution is in this case shown to be critically gauge-dependent. A direct comparison to the QF distribution, which does not exhibit this flaw, is drawn (its acknowledged drawback concerning the quantum backflow effect notwithstanding).

scholarly journals INJECTANCE AND A PARADOX

2012 ◽  
Vol 26 (03) ◽  
pp. 1250028 ◽  
Author(s):  
URBASHI SATPATHI ◽  
P. SINGHA DEO
Keyword(s):  
Quantum Mechanics ◽  
Time Delay ◽  
Physical Quantity ◽  
Time Delays ◽  
Interference Effects ◽  
Classical Formula ◽  
Quantum Regime ◽  
Negative Time

Quantum mechanics manifests in experimental observations in several ways. Hauge et al. (1987) and Leavens et al. (1989) had pointed out that interference effects dominate a physical quantity called injectance. We show that, very paradoxically, the interference related term vanish in a quantum regime making semi-classical formula for injectance exact in this regime. This can have useful implications to experimentalists as semi-classical formulas are much more simple. There are other puzzling facts in this regime like an ensemble of particles that can be transmitted without any time delay or negative time delays.

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