Steven Weinstein | |
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Education |
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Scientific career | |
Fields | Philosophy of Physics, Philosophy of Science |
Institutions | University of Waterloo, Perimeter Institute for Theoretical Physics |
Website | http://arts.uwaterloo.ca/~sw |
Steven Weinstein is a philosopher at the University of Waterloo, [1] noted particularly for his work on quantum gravity, time, and the interpretation of quantum mechanics. [2]
Weinstein studied as an undergraduate student at Princeton University, from where he graduated with honors with an A.B. in philosophy in 1982 after completing a 54-page-long senior thesis titled "Quarks and Qualia." [3] After several years of writing, recording, and performing music, [4] he returned to academic work, obtaining his Ph.D. in Philosophy from Northwestern University in 1998, supervised by Arthur Fine. He is presently a professor in the Philosophy Department at the University of Waterloo, with a cross-appointment in Physics. He is also an Affiliate member of the Perimeter Institute for Theoretical Physics.
His research is in the interpretation of quantum theory and the nature of space, time, and space-time. He has explored the possibility of multiple time dimensions. In a joint paper with Walter Craig, they gave the first well-posed initial value problem for the wave equation in more than one time dimension (the ultrahyperbolic equation). He has written critically on anthropic reasoning in cosmology, and most recently was the co-recipient (along with George Francis Rayner Ellis) of the 2nd Prize in the Foundational Questions Institute (FQXi) essay contest on "Questioning the Foundations" for his paper 'Patterns in the fabric of nature', which proposes that non-local constraints may play a role in fundamental physics and may help explain both large-scale (cosmological) and small-scale (quantum) correlations. [5] His work on multiple time dimensions was featured on Through the Wormhole with Morgan Freeman. [6]
Recent work involves using energy-based machine learning models to "learn" EPR correlations, the success of which suggests a route toward an acausal hidden-variable theory underlying quantum mechanics.
The anthropic principle, also known as the observation selection effect, is the hypothesis that the range of possible observations that could be made about the universe is limited by the fact that observations are only possible in the type of universe that is capable of developing intelligent life. Proponents of the anthropic principle argue that it explains why the universe has the age and the fundamental physical constants necessary to accommodate intelligent life. If either had been significantly different, no one would have been around to make observations. Anthropic reasoning has been used to address the question as to why certain measured physical constants take the values that they do, rather than some other arbitrary values, and to explain a perception that the universe appears to be finely tuned for the existence of life.
The many-worlds interpretation (MWI) is an interpretation of quantum mechanics that asserts that the universal wavefunction is objectively real, and that there is no wave function collapse. This implies that all possible outcomes of quantum measurements are physically realized in different "worlds". The evolution of reality as a whole in MWI is rigidly deterministic and local. Many-worlds is also called the relative state formulation or the Everett interpretation, after physicist Hugh Everett, who first proposed it in 1957. Bryce DeWitt popularized the formulation and named it many-worlds in the 1970s.
Quantum gravity (QG) is a field of theoretical physics that seeks to describe gravity according to the principles of quantum mechanics. It deals with environments in which neither gravitational nor quantum effects can be ignored, such as in the vicinity of black holes or similar compact astrophysical objects, as well as in the early stages of the universe moments after the Big Bang.
An interpretation of quantum mechanics is an attempt to explain how the mathematical theory of quantum mechanics might correspond to experienced reality. Quantum mechanics has held up to rigorous and extremely precise tests in an extraordinarily broad range of experiments. However, there exist a number of contending schools of thought over their interpretation. These views on interpretation differ on such fundamental questions as whether quantum mechanics is deterministic or stochastic, local or non-local, which elements of quantum mechanics can be considered real, and what the nature of measurement is, among other matters.
In quantum mechanics, wave function collapse, also called reduction of the state vector, occurs when a wave function—initially in a superposition of several eigenstates—reduces to a single eigenstate due to interaction with the external world. This interaction is called an observation and is the essence of a measurement in quantum mechanics, which connects the wave function with classical observables such as position and momentum. Collapse is one of the two processes by which quantum systems evolve in time; the other is the continuous evolution governed by the Schrödinger equation.
The Big Bounce hypothesis is a cosmological model for the origin of the known universe. It was originally suggested as a phase of the cyclic model or oscillatory universe interpretation of the Big Bang, where the first cosmological event was the result of the collapse of a previous universe. It receded from serious consideration in the early 1980s after inflation theory emerged as a solution to the horizon problem, which had arisen from advances in observations revealing the large-scale structure of the universe.
In theoretical physics, the anti-de Sitter/conformal field theory correspondence is a conjectured relationship between two kinds of physical theories. On one side are anti-de Sitter spaces (AdS) that are used in theories of quantum gravity, formulated in terms of string theory or M-theory. On the other side of the correspondence are conformal field theories (CFT) that are quantum field theories, including theories similar to the Yang–Mills theories that describe elementary particles.
In theoretical physics, the hierarchy problem is the problem concerning the large discrepancy between aspects of the weak force and gravity. There is no scientific consensus on why, for example, the weak force is 1024 times stronger than gravity.
In quantum mechanics, the measurement problem is the problem of definite outcomes: quantum systems have superpositions but quantum measurements only give one definite result.
In theoretical physics, fine-tuning is the process in which parameters of a model must be adjusted very precisely in order to fit with certain observations.
In string theory, the string theory landscape is the collection of possible false vacua, together comprising a collective "landscape" of choices of parameters governing compactifications.
Helen Fay Dowker is a British physicist who is a current professor of theoretical physics at Imperial College London.
The possibility that there might be more than one dimension of time has occasionally been discussed in physics and philosophy. Similar ideas appear in folklore and fantasy literature.
In mathematical physics, de Sitter invariant special relativity is the speculative idea that the fundamental symmetry group of spacetime is the indefinite orthogonal group SO(4,1), that of de Sitter space. In the standard theory of general relativity, de Sitter space is a highly symmetrical special vacuum solution, which requires a cosmological constant or the stress–energy of a constant scalar field to sustain.
In cosmology, the cosmological constant problem or vacuum catastrophe is the substantial disagreement between the observed values of vacuum energy density and the much larger theoretical value of zero-point energy suggested by quantum field theory.
In theoretical physics, shape dynamics is a theory of gravity that implements Mach's principle, developed with the specific goal to obviate the problem of time and thereby open a new path toward the resolution of incompatibilities between general relativity and quantum mechanics.
A black hole firewall is a hypothetical phenomenon where an observer falling into a black hole encounters high-energy quanta at the event horizon. The "firewall" phenomenon was proposed in 2012 by physicists Ahmed Almheiri, Donald Marolf, Joseph Polchinski, and James Sully as a possible solution to an apparent inconsistency in black hole complementarity. The proposal is sometimes referred to as the AMPS firewall, an acronym for the names of the authors of the 2012 paper. The potential inconsistency pointed out by AMPS had been pointed out earlier by Samir Mathur who used the argument in favour of the fuzzball proposal. The use of a firewall to resolve this inconsistency remains controversial, with physicists divided as to the solution to the paradox.
Sandu Popescu is a Romanian-British physicist working in the foundations of quantum mechanics and quantum information.
Quantum foundations is a discipline of science that seeks to understand the most counter-intuitive aspects of quantum theory, reformulate it and even propose new generalizations thereof. Contrary to other physical theories, such as general relativity, the defining axioms of quantum theory are quite ad hoc, with no obvious physical intuition. While they lead to the right experimental predictions, they do not come with a mental picture of the world where they fit.
Robert W. Spekkens is a Canadian theoretical quantum physicist working in the fields of quantum foundations and quantum information.
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