Time reversal noninvariance in quantum mechanics and in nonlinear optics (original) (raw)
Related papers
On the time reversal noninvariance in quantum physics
A brief review of the main direct and indirect experimental proofs of the nonequivalence of forward and reversed processes in nonlinear optics is presented. The main consequences of this nonequivalence and the ways of its experimental study are discussed.
The arrow of time in quantum mechanics and in nonlinear optics
The direct and indirect experimental proofs of a strong time invariance violation in optics are discussed. Time noninvariance for present day becomes the only real physical base for explanation the origin of the most phenomena in nonlinear optics. This is a good cause to introduce the time asymmetry into the dynamical equations of the basic laws of physics.
Solving the Puzzle of Time Reversal in Quantum Mechanics: A New Approach
Why does time reversal involve two operations, a temporal reflection and the operation of complex conjugation? Why is it that time reversal preserves position and reverses momentum and spin? This puzzle of time reversal in quantum mechanics has been with us since Wigner's first presentation. In this paper, I propose a new approach to solving this puzzle. First, I argue that the standard account of time reversal can be derived from the requirement that the continuity equation in quantum mechanics is time reversal invariant. Next, I analyze the physical meaning of the continuity equation and explain why it should be time reversal invariant. Finally, I discuss how the new analysis help solve the puzzle of time reversal in quantum mechanics.
A CONCEPTUAL EXPERIMENTAL VIOLATION OF TIME REVERSAL SYMMETRY
The equations of quantum mechanics are time reversal symmetric. Here we use a simple conceptual double slit experiment to show that under certain circumstances time reversal symmetry is violated. We send a single particle from a source through a double slit to a detecting screen. Irrespective of how we reverse the momentum of the particle at the screen, we expect that it is unlikely to return to the original source. We interpret this to mean that when the position at which the particle arrives is probabilistically determined, time reversal symmetry is violated. Looking at the experiment in quantum mechanical term, we find the need to use a random unitary matrix in the equation giving the time evolution of the state of the system. This is due to a selection process that takes place during a measurement, wherein a system that can be in any of a number of states randomly ends up in only one of those states. This equation is not time reversal symmetric.
Microscopic Irreversibility: Looking for a Microscopic Description of Time Asymmetry
Journal of Statistical Physics
This paper is an attempt to understand time-reversal asymmetry better by developing the quantitative description of that asymmetry. The aim is not to explain the asymmetry, but to describe it in more detail. Two model systems are considered here; one is the classical Lorentz gas, the other a quantum Lorentz gas. In the classical case, it is argued that the distribution of the directions of motion of particles that are about to hit an obstacle is qualitatitvely different from the analogous distribution for particles that have just hit the obstacle (an entropy-like functional of the velocity distribution function is used to characterize the asymmetry). In the quantum case, a similar distinction is drawn between the density matrix describing particles that have not yet encountered an obstacle and the one describing particles that have hit an obstacle or are in the process of doing so.
TIME-REVERSAL SYMMETRY AND TIME-DEPENDENT PHYSICS
Foundations of Physics Letters, 2000
In this letter I study the concept of time-reversal invariance in both classical and quantum physics in the absence of time-translation invariance (explicit time dependence/external time-dependent fields). Accordingly I generalize the concept of time-reversed process when the time-origin of the process has physical significance. The cases of classical physics, standard quantum mechanics and time-neutral quantum mechanics with and without explicit time dependence are discussed.
2008
Based on Document (1), by considering the retarded interaction of radiation fields, the third order transition probabilities of stimulated radiations and absorptions of light are calculated. The revised formulas of nonlinear polarizations are provided. The results show that that the general processes of non-linear optics violate time reversal symmetry. The phenomena of non-linear optics violating time reversal symmetry just as sum frequency, double frequency, different frequencies, double stable states, self-focusing and self-defocusing, echo phenomena, as well as optical self-transparence and self absorptions and so on are analyzed.