Theories Definition and 466 Threads

Hey there This may sound a bit silly to a lot of 'experts' but, what are the differences between standard qunatum mechanics, quantum field theory, and quantum electrodynamics? Are they all predicting different aspects of natures workings, or has one superseded another? I get confused...

As per the subject. Where on the net can I post a personal hypothesis for feedback from people who are qualified to comment?

Hey guys, I have been thinking about the problem of mathematical truths. We simply do not know if the things that mathematics deals with really exist or not, yet people still believe that its statements are true and indubitable. Unfortunately, the only truly well-respected theory of truth in the...

Are Lattice Gauge Theories still considered an area of active physics research? (i.e., are people still producing PhDs in this subject?) Or has this research area become passe?

I am starting this thread with an observation and three questions. I post this only as a starting point. I would appreciate any comment on the search for a unified theory. I am an amateur physicist at best, yet it often seems as though the scientific world over complicates the search for...

The evidence points to an expanding universe, we tell this by looking at the redshift/distance relationship, objects further away are receding faster, with their redshift and distance at an almost linear relation. My question is, the photons emitted by those objects that we are just now...

[SIZE="3"]I'm not a science student - quite a layman. So, please keep your replies simple and straightforward. Thanks. Why are there more than one theory on acid-base? Why isn't one theory enough? Are these theories inter-compatible? Does one theory try to counter the limitations of earlier...

"In principle" limitations of hidden variable theories Does this mean that the "hidden variable" is the factor the knowledge of which is limited in principle? What I am wondering about is to what extent such factor can be said to exist if they cannot be know in principle. I'm sorry if...

Suppose I am simple man, who studies in home and read some scientific journals . Could I be able to deliver some theories(and would it be possibly correct ?. Would I have to be engaged in big laboratories consiting super computers, advance telescopes etc? How was eeinstein became able to...

Does anyone know of any well-motivated theories of gravity -- preferably viable ones -- that have nonzero values of the PPN ζ parameters, which describe momentum nonconservation? In http://relativity.livingreviews.org/Articles/lrr-2006-3/articlesu6.html#x12-200003.3 , table 3 shows some...

I keep seeing references to UV and IR in references to string theory and quantum gravity. This seems to come up in discussions of renormalization especially. Can someone please explicitly explain the term? Google doesn't seem to help here. There are way too many references. I have tried...

By 'equivalence', I mean of the computational kind -- i.e. in the same way any universal computer can emulate any other. First of all, hi there, I'm not sure I put this question in exactly the right forum, but it seems to me that most dualities currently being discussed fall under the...

Hi, I'm currently reading "Supersymmetry demystifed" by Patrick Labelle, chapter 10, about SUSY non-Abelian gauge theories. We have a Lagrangian with SU(N)-gauge fields, and gaugino's. What puzzles me are the following claims of Labelle about the representations. In the...

Why are theories of Quantum Mechanics and Relativity not possible to combine? I read this on wikipedia and heard this on a documentary on TV.

Two decades ago, Gribov copies arising in the Lorentz- or Coulomb gauge were considered problematic in non-perturbative calculations, e.g. due to potential failure of cluster decomposition (are there other reasons?) In the meantime this bug turned into a feature, as IR properties, especially...

i really cannot understand what contravariant and covariant mean why do we need the machinery of raising and lowering the indices? i think at least in pure mathematics, we do not need this type of trashes i cannot see how this notation will not cause any inconsistency it is really...

Greetings. For your information, I am an undergraduate college student studying electrical engineering and also intend to get a degree in particle physics. At this point in time I am only beginning to learn calculus. For the past several years I’ve been watching television documentaries...

I have a question regarding quantization. In most cases one never starts with a quantum theory, but always writes down a classical expression, goes through quantization, implementation of constraints (Dirac, BRST, ...), construction of Hilbert space, inner product, measure of an path integral...

You would feed it experimental data and it would generate theories or mathematical structures which fit the data. The theories would then be run against related experimental data to see if the theory also predicted them as well. Slight mutations, mating successful ones ---> evolved theory...

It is common lore to write lagrangians in field theories in the form L(t)=\int d^{3}x\mathcal{L}(\phi_{a},\partial_{\mu}\phi_{a}). Nonetheless, is there any particular reason for doing that? Why do we neglect higher order derivatives? Does it mess around with Lorentz invariance or something...

Do "infinite probabilities" hurt multiverse theories? I got some good responses to my last thread on here I thought I'd try one more. I'm wondering about the multiverse theories where whenever a quantum 'decision' is made, the universe branches out into versions of itself in which each of the...

The almost simultaneous detection of low energy and high energy photons puts tight constraints on models predicting linear dependence of c on E. But it's very far from ruling out quadratic dependence. My question is, why do Lorentz-violating theories commonly predict linear rather than quadratic...

can anyone give me a good book recommendation for the newest theories in astro-physics? in reletively layman's terms

Anybody watch Inception yet? What are your theories? What is the answer?

Hi, I have a short question about gauge theories and constraints. Imagine I have a symmetry algebra, and I gauge it. With N generators in the algebra I get N gauge fields and N gauge curvatures. In realizing the algebra on the gauge fields I assume the gauge parameters are independent and...

In thinking about specific heat, I have been unable to resolve a particular issue. If molecules in a substance are bumped and move faster, then they will measue to be at a temperature proportional to the speed they are moving which is a consequence of how hard on average they were hit(heat...

I derived an equation describing the free surface of an electrified fluid. I am currently seeking traveling wave solutions for this problem, the equation I am looking at is (1-F) f+\frac{1}{90}h^{4}f^{(4)}+\frac{3}{4h}f^{2}-\frac{1}{2}\Bigg( B-\frac{1}{3}\Bigg)...

I have been working on the problem of electrified fluid flow down a channel with a moving pressure distribution. I have derived an equation which describes the free surface of said fluid flow which is a Benjamin-Ono like equation. I have a numerical solution for this equation and it gives the...

Hi all, I've just started reading upon quantum physics and came across Max Planck. I believe he was the one to state that the oscillating atoms or molecules that emit radiation could only occupy quantum states, whereby photons with energy according to E=hf are emitted when an atom changes...

Hi I'm not a science student neither of mathematics. I have a understanding of mathematics and physics topics up to high school - calculus etc. I was thinking of learning about relativity which is quite contrary to common sense, for fellows like me. I was look at this...

Until recently, I thought that any theory that contains non-renormalizable interactions in the power-counting sense (i.e. those whose couplings have negative mass dimension) must be an 'effective' theory that necessarily breaks down at some energy. However, I've been looking at Weinberg's QFT...

That explain cosmic microwave background ? Cosmic microwave background (referring to the hiss that was detected by Wilson and Penzias, using microwave wavelength satellites, and it is found everywhere) and it is evidence of the big bang, but is it evidence of anything else? Are there other...

Hey all, I'm a senior in high school doing a research report on all the various Theories of Everything in physics. I'm familiar with most of them and have a basic understanding of the concepts behind them. I'm starting this thread to get a better understanding on people's general opinions on...

The field theories in the standard model haven't been shown to be mathematically consistent. Do "effective field theories" bypass this difficulty? Are they completely mathematically well-defined as an approximation? Of course, if the deeper underlying theory is another QFT or string theory, you...

This paper was a "sleeper" for much of the past 16 years. But in the past 12 months, since March 2009, it has received 8 citations. Just random fluctuation or can we point to something that stirred up interest? http://arxiv.org/abs/gr-qc/9406019 Von Neumann Algebra Automorphisms and...

From a very very brief http://www.newscientist.com/article/dn18612-knowing-the-mind-of-god-seven-theories-of-everything.html?page=1"of seven competing theories for a Theory of Everything: from New Scientist: 15:33 04 March 2010 by Michael Marshall 1. String theory 2. Loop quantum gravity...

Are quantum gravity theories trying to progress on the assumption that there are such things as gravitons?

Okay, so I've gone through calc I - III with Stewart's Calculus... I'm happy with the book for the most part, but I want a bit more theory now. I don't care what type of book, it could be like a pop-sci book for all I care, I just want to read about the theories behind the calculus without going...

I had this discussion about the differences between hypotheses, theories, and laws in my physical science class today, and I suddenly remembered the principles I had learned about in physics (e.g. Bernoulli's principle, Pauli exclusion principle). I was curious how principles fit into this whole...

I'm just curious, what was the first reactions to Einstein's theories (it was 1905, right?) ... were they refuted or supported? was it like "Oh! these are nonsense..these are pseudoscience .. we shall burn you"?! or were they garnered respectable amount of debate?... were they supported by...

I was just curious as to when science goes from fact to theory? What do we know to be absolute? Are balck holes for example still theory? Is GR and SR still only theory? Where is our line of absolute fact?

What do the phenomenologists of unified theories (strings, loops etc) try to match at lower energies when there are so many conflicting theories lying around at these energies? I understand that certain things should be there in any model - like chiral matter, three generations etc - but a lot...

Hi Everyone, I hope everyone had a very enjoyable holiday season. Currently I'm developing a short film to shoot later this year. Being ever fascinated with the natural universe and also theoretical physics this film will be a welcome new approach to the science fiction genre. The goal is...

Why are personal and "crack" theories not allowed? I always wondered about this rule. This is a skeptics section of the forum and if you have something to say, well wouldn't it be reasonable to question it and take it apart than to rather disown it? I asked a question earlier about Forces by...

How can I publish my own Physics Theories ? or Where can I Publish my theories ? Officially to the scientific community ??.. so, that they can accept it.if it's correct and than give me copy right ?? How 2 get my theory registered ? I have lot of awesome ideas that can change our world of...

Hi! This is my first post. I have a question of cosmological importance - literally and figuratively. The Standard Model is the most accepted theory of (almost) everything, yet is unable to make sense of gravity. String Theory can explain it all theoretically through quantitative...

One thing I don't understand is that most of our theories include particles...the oversimplified analogy is, of course, balls on a billiard table. Even the "theory of everything" or String Theory/M-theory tries to explain everything with one particle and one force. My question is this...why do...

Hi, In this other thread https://www.physicsforums.com/showthread.php?t=354424" I was hoping to get a scientific answer to my question. Apparently this was not an easy question or hypothesis that was easily falsified. I was sorry to see the subject turned into a unpleasant debate which ended up...

Is anyone currently working on new theories unifying matter and fields that differ from string theory?

Both purport to make use of condense matter- models to model fundamental physics. What are the differences and which seems more promising?