What is the correct Unified Field Theory?
150007
At the moment no one knows.\n\nString theories are one attempts to combine Quantum Mechanics and General Relativity, which is what a unified theory is. Thus far no complete theory and no testable predictions have emerged. Perhaps they will in time, or from some of the alternatives like loop gravity.
549041
Short answer it is meant to unify the supersting theories (which are of course aimed at answering the most fundamental question of the most elementary (sub)particles).\n\nLonger answer, there are dualities in the five "original" string theories. These dualities lead to the same pursuit as in the Grand Unification theory when people started thinking of more elegant theories. The M (or U) theory is basically the  grand unification of the five string theories. \n\nThe theory has a huge problem like the "originals", too many dimensions. Just as you can fit a polynomial of nth degree to any data, given enough dimensions you can explain any physical occurrence with almost any explanation this is why scientists are still dismissive of the M and String theories (except the guys who try to convince the rest)
156513
http://theory.uwinnipeg.ca/physics/
944656
In general all interactions should be introduced when you write your Energy-Momentum tensor... If you include the electromagnetic term then there would be a solution for general relativity including magnetic forces. This is actually done with for example rotating black holes with strong magnetic fields..
42946
There are two major theories of modern physics: Quantum Mechanics and General Relativity. Both work well, with QM being applicable to atomic and smaller sizes, and GR to large (Solar size, galaxy size, etc.) things.\n\nThe major question in physics today is: how do we combine QM and GR so that they are two aspects of one larger theory. This postulated theory is usually called a Unified Theory or Theory of Everything or something like that. String theories are attempts to do this (so far all are still incomplete).\n\nThe major difference between QM and GR is that nn QM energy comes in discrete levels (all way to small for us to notice). However in GR space-time is continious. So it is not instantly clear whether space-time is continous or quantized in a unified theory.\n\nFor consistency between these space quantization would have to be on extremely small scales. This would almost certain occur (if it did) at distances called the Planck length, which is ~ 10^-33 cm. (This is about one billion trillion times smaller than an atomic nucleus.)\n\nQuantization of time would then be the interval for light to cross this distance, about 10^-43 seconds. It is because of a lack of a unified theory that physicists can't say anything about the conditions of the universe before 10^-43 seconds after the Big Bang. (Of course that is still pretty good.)\n\nThe short answer is: no one knows, but the scale of quantization would have to be much, much smaller than any known elementary particle.
507841
Quantum theory and its relation with general theory of relativity
187216
Plenty of physicists today still believe that the elusive Theory of Everything (or Grand Unified Theory) is something that does exist, however, I don't think very many people are actually actively looking for it. The biggest problem at the moment in regards to some sort of unified theory, is that there is no rectifying quantum theory with general relativity (as which would be needed to describe black holes, for example).\n\nBut yeah, I think that it is possible, considering that all evidence suggests that we are rational beings in a rational world. I'd like to find it myself!\n\nAs for whether Einstein would have been able to prove it, I really doubt that. He spent the final years of his life trying to disprove the inherent uncertainty in the universe that quantum theory requires. From what I've been taught, most people think that his talents were wasted on this vain effort; they are happy to accept the Copenhagen interpretation, and don't much care if, upon deeper examination, it does result in fundamental order and certainty. The mathematics work, and it has been proven... there's no problem with it unless you don't like the philosophical implications.
262094
Quantum Field Theory (a theory dealing with forces as particle exchanges between discrete probabilistic phenomena) and General Relativity (a theory dealing with force as smooth spacetime manifolds). So the problem becomes trying to create a theory where gravity also has a force carrier particle with properties akin to the other forces.\nThe reconciliation of these two theories is the subject of modern membrane (M) theories. See the sources for details.
1099566
I am just answering you but... I like applied physics. I don't like the theorists that lose themselves in tricky constructions. For simplicity (Occam) better believe in one and only universe. \n\nhttp://en.wikipedia.org/wiki/Many-worlds_interpretation\n\nCheck the external links at wikipedia.\n\nHere is something I have found:\n:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::\nQ1 Who believes in many-worlds?\n"Political scientist" L David Raub reports a poll of 72 of the "leading cosmologists and other quantum field theorists" about the "Many-Worlds Interpretation" and gives the following response breakdown [T].\n\n        \n1) "Yes, I think MWI is true"                    58%\n2) "No, I don't accept MWI"                      18%\n3) "Maybe it's true but I'm not yet convinced"   13%\n4) "I have no opinion one way or the other"      11%\n\nAmongst the "Yes, I think MWI is true" crowd listed are Stephen Hawking and Nobel Laureates Murray Gell-Mann and Richard Feynman. Gell-Mann and Hawking recorded reservations with the name "many-worlds", but not with the theory's content. Nobel Laureate Steven Weinberg is also mentioned as a many-worlder, although the suggestion is not when the poll was conducted, presumably before 1988 (when Feynman died). The only "No, I don't accept MWI" named is Penrose.\n\nThe findings of this poll are in accord with other polls, that many- worlds is most popular amongst scientists who may rather loosely be described as string theorists or quantum gravitists/cosmologists. It is less popular amongst the wider scientific community who mostly remain in ignorance of it.\n\nMore detail on Weinberg's views can be found in _Dreams of a Final Theory_ or _Life in the Universe_ Scientific American (October 1994), the latter where Weinberg says about quantum theory:\n"The final approach is to take the Schrodinger equation seriously [..description of the measurement process..] In this way, a measurement causes the history of the universe for practical purposes to diverge into different non-interfering tracks, one for each possible value of the measured quantity. [...] I prefer this last approach"\n\nIn the The Quark and the Jaguar and Quantum Mechanics in the Light of Quantum Cosmology [10] Gell-Mann describes himself as an adherent to the (post-)Everett interpretation, although his exact meaning is sometimes left ambiguous.\n\nSteven Hawking is well known as a many-worlds fan and says, in an article on quantum gravity [H], that measurement of the gravitational metric tells you which branch of the wavefunction you're in and references Everett.\n\nFeynman, apart from the evidence of the Raub poll, directly favouring the Everett interpretation, always emphasized to his lecture students [F] that the "collapse" process could only be modelled by the Schrodinger wave equation (Everett's approach).\n\n[F] Jagdish Mehra The Beat of a Different Drum: The Life and Science Richard Feynman\n[H] Stephen W Hawking Black Holes and Thermodynamics Physical Review D Vol 13 #2 191-197 (1976)\n[T] Frank J Tipler The Physics of Immortality 170-171
1058278
A Grand Unified Theory of Everything cannot be explained in such fashion. I would recommend reading "Hyperspace" by Michio Kaku.
443065
because according to general relativity E=mc^2, so you can say that energy is a form of mass, but when you include this to the uncertainty principle it's incorrect to say that void has no energy (x & v = 0) so you have to go the other way, since there's a lot of void out there you should have the equivalent mass, and since mass is gravity we should be seeing the BIG CRUNCH right now, obviously that ain't happening, so one of the two theories must be wrong, but scientists prefer to say that both of 'em r parcially or entirely wrong
325710
I can't help with Unified Theory, but here's the way a professor explained string theory to me.\n\nImagine that you have a tightrope, and that an elephant is walking on it.  To that elephant, there is only one dimension - the elephant can move forward, and it can move backwards, but it can only move along that straight line.\n\nNow picture that same tightrope, but instead of an elephant, an ant is walking along it.  Like the elephant, the ant can also move forwards and back along the tightrope.  However, the ant can also walk all the way around the tightrope (apparently ants are good at clinging to things while upside-down).  For the ant, there are two possible dimensions - the forward and back one, and the around one.\n\nString theory is basically the idea that there are more dimensions than we realize.  We as humans are the elephant of the previous example - we see only three dimensions, with a potential 4th in terms of time.  According to string theory, there are ants in the world that can access more than these three or four dimensions that we are aware of.  String theorists are currently trying to prove that this is the case.
526886
In order:\n\n1) Red, blue, and green colour charges are distinct, but arbitrary, exactly like + and - electrical charges.  There is a difference between something positively charged and something negatively charged.  With quarks, it's simply that there are three different kinds of charge, instead of just two for electromagnetism.\n2) Because gluons are, themselves, influenced by the strong force, a correct description of the quantum force diagrams (penguin diagrams, if you know that term) must necessarily include higher order interactions than simply quark <-> gluon <-> quark.  The one you propose is, I believe, possible by the rules governing the quantum behaviour of quarks and gluons, as are many, many more distinct diagrams.\n3) There is no meaningful order.  RBG and RGB are both "colourless".\n4) String theory is outside of my area of expertise, I don't think I can address this issue in any meaningful way.
636004
In theoretical physics, a supergravity theory is a field theory combining supersymmetry and general relativity.\n\nLike any field theory of gravity, a supergravity theory contains a spin-2 field whose quantum is the graviton. Supersymmetry requires the graviton field to have a superpartner. This field has spin 3/2 and its quantum is the gravitino. The number of gravitino fields is equal to the number of supersymmetries. Supergravity theories are often said to be the only consistent theories of interacting massless spin 3/2 fields.\nFour Dimensional SUGRA\n\nSupergravity, also called SUGRA, was initially proposed as a four-dimensional theory in 1976, but was quickly generalized to many different theories in various numbers of dimensions. Some supergravity theories were shown to be equivalent to certain higher-dimensional supergravity theories via dimensional reduction. The resulting theories were sometimes referred to as Kaluza-Klein theories, as Kaluza and Klein constructed, nearly a century ago, a five-dimensional gravitational theory which reduces to four-dimensional electromagnetism when the fifth dimension is a circle.\n[edit]\n\n11d: The Maximal SUGRA\n\nOne of these supergravities, the 11-dimensional theory, generated considerable excitement as the first potential candidate for the theory of everything. This excitement was built on four pillars, two of which have now been largely discredited:\n\n    * Werner Nahm showed that 11 dimensions was the largest number of dimensions consistent with a single graviton, and that a theory with more dimensions would also have particles with spins greater than 2. These problems are avoided in 12 dimensions if two of these dimensions are timelike, as has been often emphasized by Itzhak Bars.\n\n    * Shortly afterwards, Ed Witten showed that 11 was the smallest number of dimensions that was big enough to contain the gauge groups of the Standard Model, namely SU(3) for the strong interactions and SU(2) times U(1) for the electroweak interactions. Today many techniques exist to embed the standard model gauge group in supergravity in any number of dimensions. For example, in the mid and late 1980s one often used the obligatory gauge symmetry in type I and heterotic string theories. In type II string theory they could also be obtained by compactifying on certain Calabi-Yau's. Today one may also use D-branes to engineer gauge symmetries.\n\n    * In 1978, Eugene Cremmer, Bernard Julia and Joel Scherk (CJS) of the Ecole Normale Superieure found the classical action for an 11-dimensional supergravity theory. This remains today the only known classical 11-dimensional theory with local supersymmetry and no fields of spin higher than two. Quantum-mechanically, inequivalent 11-dimensional theories are known which reduce to the CJS theory in the classical limit, that is when one imposes the classical equations of motion. For example, in the mid 1980s Bernard de Wit and Hermann Nicolai found an alternate theory in D=11 Supergravity with Local SU(8) Invariance. This theory, while not manifestly Lorentz-invariant, is in many ways superior to the CJS theory in that, for example, it dimensionally-reduces to the 4-dimensional theory without recourse to the classical equations of motion.\n\n    * In 1980, Peter G. O. Freund and M. A. Rubin showed that compactification from 11 dimensions preserving all the SUSY generators could occur in two ways, leaving only 4 or 7 macroscopic dimensions (the other 7 or 4 being compact). Unfortunately, the noncompact dimensions have to form an anti de Sitter space. Today it is understood that there are many possible compactifications, but that the Freund-Rubin compactifications are invariant under all of the supersymmetry transformations that preserve the action.\n\nThus, the first two results appeared to establish 11 dimensions uniquely, the third result appeared to specify the theory, and the last result explained why the observed universe appears to be four-dimens
43519
It hasn't been "proven" wrong, but there are several alternatives.  Check these sources for in depth information.  I got this information from James P. Hogan's "Kicking the Sacred Cow: Questioning the Unquestionable and Thinking the Impermissible", which covers evolution, cosmology, physics, environmentalism, AIDS, and the general attitude that the most prevalent theories must be right.
103375
You know, this is so easy to answer with a simple web search that I somewhat annoyed that you bothered to ask it here. Do you not know how to use google or yahoo or altavista?\n\nThese two postulated but undiscovered particles are completely different and have completely different properties. For example:\n\nThe postulated Higgs Boson produces mass.\nThe postulated graviton transmits gravitational force between things with mass.\n\nThe Higgs Boson has spin 0.\nThe graviton has spin 2. \n\nThe Higgs Boson has a nonzero rest mass. \nThe graviton has a rest mass of zero. \n \n\nAnd so on.
1160647
Neither,\n\nTheory is never proof so that's not it. Gravity is a weak force. M is an explanation why it is weak. Multidimensional theory is not about gravity, it's just part of it.\n\nEinstein tried to unify the fields, he failed. Many new theories came and went.... I'm not sure we 'got it' now. It is still a very unstable work in progress.