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When physicists are asked about “parallel worlds” or ideas along those lines, they have to be careful to distinguish among different interpretations of that idea. There is the “multiverse” of inflationary cosmology, the “many worlds” or “branches of the wave function” of quantum mechanics, and “parallel branes” of string theory. Increasingly, however, people are wondering whether the first two concepts might actually represent the same underlying idea.
Subscription Center Space :: Features :: April 6, 2011 :: 24 Comments :: Email :: Print How Cosmic Inflation Creates an Infinity of Universes [Video]
In physics, the world line of an object is the unique path of that object as it travels through 4- dimensional spacetime . The concept of "world line" is distinguished from the concept of "orbit" or "trajectory" (such as an orbit in space or a trajectory of a truck on a road map) by the time dimension, and typically encompasses a large area of spacetime wherein perceptually straight paths are recalculated to show their (relatively) more absolute position states — to reveal the nature of special relativity or gravitational interactions. The idea of world lines originates in physics and was pioneered by Herman Minkowski . The term is now most often used in relativity theories (i.e., special relativity and general relativity ).
Welcome to this week’s installment of the From Eternity to Here book club . Part Three of the book concludes with Chapter Eleven, “Quantum Time.”
A density matrix is a matrix that describes a quantum system in a mixed state , a statistical ensemble of several quantum states , in contrast to a pure state , described by a single state vector . The density matrix is the quantum-mechanical analogue to a phase-space probability measure (probability distribution of position and momentum) in classical statistical mechanics . Explicitly, suppose a quantum system may be found in state
Einselection is short for e nvironment - in duced super selection , a nickname coined by Wojciech H.
Welcome to this week’s installment of the From Eternity to Here book club . Part Four opens with Chapter Twelve, “Black Holes: The Ends of Time.” Excerpt: Unlike boxes full of atoms, we can’t make black holes with the same size but different masses. The size of a black hole is characterized by the “Schwarzschild radius,” which is precisely proportional to its mass. If you know the mass, you know the size; contrariwise, if you have a box of fixed size, there is a maximum mass black hole you can possibly fit into it.