This blog enables you to understand about Black holes. It also explains related terms and theory.
Wednesday, 5 November 2014
Parallel universes – worlds where the dinosaur-killing asteroid never hit, or where Australia was colonised by the Portuguese – are a staple of science fiction. But are they real?
In a radical paper published this week in Physical Review X, we (Dr Michael Hall and I from Griffith University and Dr Dirk-André Deckert from the University of California) propose not only that parallel universes are real, but that they are not quite parallel – they can “collide”.
In our theory, the interaction between nearby worlds is the source of all of the bizarre features of quantum mechanics that are revealed by experiment. Super Weekend – Flat 40% off on over 15000 styles.
Many worlds in existing interpretations
The existence of parallel worlds in quantum mechanics is not a new idea in itself – they are a feature of one of the leading interpretations of quantum mechanics, the 1957 “many worlds interpretation” (MWI).
Now quantum mechanics is the most widely applicable and successful physical theory of all time, so you might wonder why it needs interpreting. There are two reasons.
First, its formalism is extremely remote from everyday experience. It is all based on a “wavefunction” which is like a wave, except that it lives not in ordinary three-dimensional space but in an infinite dimensional space.
Second, the so-called Bell correlations, which can be experimentally measured using distant quantum systems originating from a common source, violate the usual laws of local cause and effect.
This implies that the wavefunction formalism can’t be replaced by anything in ordinary space.
There are several competing interpretations of quantum mechanics and each one gives a quite different portrayal of the ultimate nature of reality. But each portrayal is profoundly strange in some way, because of the weirdness of quantum mechanics itself.
The strangeness of the MWI is in postulating that any time any quantum system is observed in a universe, that universe “branches” into a bunch of new universes, one for each possible outcome of the observation.
The MWI has been criticised for the fact that it doesn’t define precisely when an observation occurs. Thus it is vague about how many worlds there are at any given time, and each world is somewhat fuzzy in its properties, being described by a wavefunction.
Also, because different outcomes happen with different probabilities, the MWI has to postulate that different worlds have different “weights” – some worlds are more important than others even though they are all supposed to be real.
Finally, once they are created, these different worlds don’t interact, so some critics say they are purely hypothetical and serve no purpose.
Many interacting worlds
Our new theory also involves many worlds but there the similarity to the standard MWI ends.
First, we postulate a fixed, although truly gigantic, number of worlds. All of these exist continuously through time – there is no “branching”.
Second, our worlds are not “fuzzy” – they have precisely defined properties. In our approach, a world is specified by the exact position and velocity of every particle in that world – there is no Heisenberg uncertainty principle that applies to a single world. Indeed, if there were only one world in our theory, it would evolve exactly according to Newtonian mechanics, not quantum mechanics.
Third, our worlds do interact and that interaction is the source of all quantum effects. Specifically, there is a repulsive force of a very particular kind, between worlds with nearly the same configuration (that is, having nearly the same position for every single particle). This “interstitial” force prevents nearby worlds from ever coming to have the same configuration, and tends to make nearby worlds diverge.
Fourth, each one of our worlds is equally real. Probability only enters the theory because an observer, made up of particles in a certain world, does not know for sure which world she is in, out of the set of all worlds. Hence she will assign equal probability to every member of that set which is compatible with her experiences (which are very coarse-grained, because she is a macroscopic collection of particles). After performing an experiment she can learn more about which world she is in, and thereby rule out a whole host of worlds that she previously thought she might be in.
Putting all of the above together gives our theory – the Many Interacting Worlds approach to quantum mechanics. There is nothing else in the theory. There is no wavefunction, no special role for observation and no fundamental distinction between macroscopic and microscopic.
Nevertheless, we argue, our approach can reproduce all the standard features of quantum mechanics, including twin-slit interference, zero-point energy, barrier tunnelling, unpredictability and the Bell correlations mentioned above. Up to 50% off on Women’s Apparel.
We call our theory an “approach” rather than an “interpretation” because for any finite number of worlds our theory is only an approximation to quantum mechanics. This gives the exciting possibility that it might be possible to test for the existence of these other worlds.
The ability to approximate quantum evolution using a finite number of worlds could also be very useful. Specifically, it could be to model molecular dynamics, which is important for understanding chemical reactions and the action of drugs.
Quantum mechanics has always been a puzzle because of the subtle but deep ways it deviates from Newtonian mechanics. That these deviations could be due to a delicate interaction of essentially Newtonian worlds with “nearby” parallel worlds is an entirely new solution to the quantum puzzle.
For us at least there is nothing inherently implausible in the idea, and for fans of science fiction it makes those plots involving communication between parallel worlds not quite so far-fetched after all.
Tuesday, 4 November 2014
Multi_ _ _iverse affect ours
Parallel universes have long been a staple of science fiction. But according to a radical new theory of quantum mechanics published Oct. 23 in the journal Physical Review X, other universes are real--and they exist in vast numbers.
What's more, the scientists behind the theory say the other universes exert a subtle repulsive force on our own universe--and that this force is what makes the quantum realm so mind-bendingly bizarre.
"Any explanation of quantum phenomena is going to be weird, and standard quantum mechanics does not really offer any explanation at all--it just makes predictions for laboratory experiments," Prof. Howard Wiseman, a physicist at Griffith University in Brisbane, Australia, and one of the creators of the new "many interacting worlds" theory, told The Huffington Post in an email. "Our new explanation...is that there are ordinary (non-quantum) parallel worlds which interact in a particular and subtle way."
The theory is a new twist on the so-called "many worlds interpretation" of quantum mechanics, which dates back to the 1950s. As Wiseman explained in a written statement issued by the university:
"In the well-known 'many worlds interpretation,' each universe branches into a bunch of new universes each time a quantum measurement is made. All possibilities are therefore realized--in some universes the dinosaur-killing asteroid missed Earth. In others, Australia was colonised by the Portuguese. But critics question the reality of these other universes, since they do not influence our universe at all. On this score, our 'many interacting worlds' approach is completely different, as the name implies."
Wiseman and his collaborators--Dr. Michael Hall, also of Griffith University, and University of California, Davis mathematician Dr. Dirk-Andre Deckert--say that their theory may have important implications in the field of molecular dynamics, which is critical to understanding chemical reactions.
Does it also suggest that humans might someday be able to interact with other universes?
"It's not part of our theory...," Wiseman told Motherboard. "But the idea of interactions with other universes is no longer pure fantasy."
What do other experts make of the new theory?
Dr. Lawrence Krauss, a theoretical physicist at Arizona State University in Tempe, told The Huffington Post in an email that he was "skeptical." And a popular Czech Republic physicist wrote on his blog that while Wiseman and his collaborators had "managed to present some ideas that are at least slightly original," their paper was "another example of the fact that such efforts are a hopeless enterprise and a huge waste of time."
But Charles Sebens, a philosopher of physics at the University of Michigan in Ann Arbor, told Nature that he was excited by the approach taken by Wiseman and his collaborators.
“They give very nice analyses of particular phenomena like ground-state energy and quantum tunneling," he told the journal. “I think that together they do a nice job presenting this exciting new idea.”
Dr. L. William Poirer, professor of chemistry at Texas Tech University in Lubbock, also expressed support for the "many interacting worlds" theory. He told HuffPost Science in an email that Wiseman and his collaborators had made "an important contribution...There is no experimental evidence to support this yet, but if true, it means that their theory will make different experimental predictions than standard quantum mechanics does."
Clearly, there's no consensus. But if Wiseman is dismayed by the uneven reaction to the theory, he's not letting on.
"There are some who are completely happy with their own interpretations of QM, and we are unlikely to change their minds," he said in the email. "But I think there are many who are not happy with any of the current interpretations, and it is those who will probably be most interested in ours. I hope some will be interested enough to start working on it soon, because there are so many questions to answer."
In the meantime, the last word should probably belong to Nobel Prize-winning theoretical physicist Richard Feynman (1918-1988), who once said, "I believe I can safely say that nobody understands quantum mechanics."
_______ Theory _________ Quantum Mechanics?
Two USC researchers have proposed a link between string field theory and quantum mechanics that could open the door to using string field theory — or a broader version of it, called M-theory — as the basis of all physics.
“This could solve the mystery of where quantum mechanics comes from,” said Itzhak Bars, USC Dornsife College of Letters, Arts and Sciences professor and lead author of the paper.
Bars collaborated with Dmitry Rychkov, his Ph.D. student at USC. The paper was published online on Oct. 27 by the journal Physics Letters.
Rather than use quantum mechanics to validate string field theory, the researchers worked backwards and used string field theory to try to validate quantum mechanics.
In their paper, which reformulated string field theory in a clearer language, Bars and Rychov showed that a set of fundamental quantum mechanical principles known as “commutation rules’’ that may be derived from the geometry of strings joining and splitting.
“Our argument can be presented in bare bones in a hugely simplified mathematical structure,” Bars said. “The essential ingredient is the assumption that all matter is made up of strings and that the only possible interaction is joining/splitting as specified in their version of string field theory.”
The history of string theory
Physicists have long sought to unite quantum mechanics and general relativity, and to explain why both work in their respective domains. First proposed in the 1970s, string theory resolved inconsistencies of quantum gravity and suggested that the fundamental unit of matter was a tiny string, not a point, and that the only possible interactions of matter are strings either joining or splitting.
At present, no single set of rules can be used to explain all of the physical interactions that occur in the observable universe.
Four decades later, physicists are still trying to hash out the rules of string theory, which seem to demand some interesting starting conditions to work (like extra dimensions, which may explain why quarks and leptons have electric charge, color and “flavor” that distinguish them from one another).
At present, no single set of rules can be used to explain all of the physical interactions that occur in the observable universe.
On large scales, scientists use classical, Newtonian mechanics to describe how gravity holds the moon in its orbit or why the force of a jet engine propels a jet forward. Newtonian mechanics is intuitive and can often be observed with the naked eye.
On incredibly tiny scales, such as 100 million times smaller than an atom, scientists use relativistic quantum field theory to describe the interactions of subatomic particles and the forces that hold quarks and leptons together inside protons, neutrons, nuclei and atoms.
An invaluable framework
Quantum mechanics is often counterintuitive, allowing for particles to be in two places at once, but has been repeatedly validated from the atom to the quarks. It has become an invaluable and accurate framework for understanding the interactions of matter and energy at small distances.
Quantum mechanics is extremely successful as a model for how things work on small scales, but it contains a big mystery: the unexplained foundational quantum commutation rules that predict uncertainty in the position and momentum of every point in the universe.
“The commutation rules don’t have an explanation from a more fundamental perspective, but have been experimentally verified down to the smallest distances probed by the most powerful accelerators. Clearly the rules are correct, but they beg for an explanation of their origins in some physical phenomena that are even deeper,” Bars said.
The difficulty lies in the fact that there’s no experimental data on the topic — testing things on such a small scale is currently beyond a scientist’s technological ability.
Ans.
String Theory Underpins Quantum Mechanics?
In a radical new theory, scientists have proposed that parallel universes really do exist and they interact with one another.
Professor Howard Wiseman and Dr Michael Hall from Griffith University's Centre for Quantum Dynamics in Australia, and Dr Dirk-Andre Deckert from the University of California, have proposed that parallel universes exist, and rather than evolving independently, nearby worlds influence one another by a subtle force of repulsion.
The researchers said that such an interaction could explain everything that is bizarre about quantum mechanics.
Quantum theory is needed to explain how the universe works at the microscopic scale, and is believed to apply to all matter. But it is notoriously difficult to fathom, exhibiting weird phenomena which seem to violate the laws of cause and effect.
The "Many-Interacting Worlds" approach developed at Griffith University provides a new perspective on this.
"The idea of parallel universes in quantum mechanics has been around since 1957," said Wiseman.
"In the well-known "Many-Worlds Interpretation," each universe branches into a bunch of new universes every time a quantum measurement is made.
"All possibilities are therefore realised - in some universes the dinosaur-killing asteroid missed Earth. In others, Australia was colonised by the Portuguese.
"But critics question the reality of these other universes, since they do not influence our universe at all. On this score, our "Many Interacting Worlds" approach is completely different, as its name implies," he said.
Wiseman and his colleagues proposed that the universe we experience is just one of a gigantic number of worlds. Some are almost identical to ours while most are very different.
All of these worlds are equally real, exist continuously through time, and possess precisely defined properties, they said.
All quantum phenomena arise from a universal force of repulsion between 'nearby' (ie similar) worlds which tends to make them more dissimilar, they added.
Hall said the "Many-Interacting Worlds" theory may even create the extraordinary possibility of testing for the existence of other worlds.
"The beauty of our approach is that if there is just one world our theory reduces to Newtonian mechanics, while if there is a gigantic number of worlds it reproduces quantum mechanics," he said.
"In between it predicts something new that is neither Newton's theory nor quantum theory.
"We also believe that, in providing a new mental picture of quantum effects, it will be useful in planning experiments to test and exploit quantum phenomena," Hall said.
The study was published in the journal Physical Review X.
