Modern and Theoretical Physics

In Quantum mechanics, position is an operator while time is just a parameter. In Quantum Field Theory, time and position are both parameters. For a successful Quantum Gravity theory, shouldn't space and time be operators? Have there been any notable attempts at a quantum theory with space and time as operators instead of parameters?

thought of sth: what is the criterion that a cubic crystal with one atom in the primitive unit cell be stable against small homogeneous deformations? what restrictions are thereby placed on the elastic stiffness constants?

If the LHC at CERN does create mini black hole(s) and in the race between hawking radiation and matter munching the latter wins... How long would it take for the Earth to be destroyed?

I glanced at it, been hearing about it. In General Time Studies, where: x=known, z=unknown, t(z)=limiting factor, t(x)=forward study, Then, x-z=t(x)+(t(z)-t(x))=t(z)=Cancellation Method and/or refining. In this validity, what is the approximate time-study analysis, for verification. I know with today's fast pace, it has to be related. And, why is it that error studies hasn't approached it's level I was aware of. An old computer class I took was Error Handling. Which would prevent round off error and such. And, I'm a knowin' that 'dem 'puters are involved. http://www.amazon.com/Integral-Discrete-Transforms-Applications-Mathematics/dp/0824782526…

I'm really confused about these physics, even though they are, for the most part, science fiction. These ideas are inspired by a video-game called "portal" where you solve puzzles with a portal gun, which fires an orange portal and a blue portal, which are essentially holes. Stick your arm through an orange portal, you see it going out the blue portal. Here is a link to some gameplay footage, portals are hard to explain. May contain spoilers. This, apart from being purely imaginary and far far into the future (if in it at all) make some interesting possibilities. First off, all the amazing possibilities of infinite loops. If you put a portal on …

I recently thought of something; since photons travel at the speed of light they are moving 0% through time (very crudely put, I know). So what would happen if they came in contact with a powerful gravitational field? Since gravity causes time to slow down as well as velocity, wouldn't that mean that photons would travel back in time? Since they'd be moving through time slower than not at all.

How come radioactive decay is not influenced by changes in temperature or the action of strong oxidizers/reducers? Thanks.

Okay, I am assuming ya'll know what the casimir effect/force is. If you don't look it up on Wiki. My question is simple, what happens to a small hollow tube do to the casimir effect?

can u freeze[pause] time at 0K? because time is relative to mass and energy and if theoretically particles stop moving at 0K does that mean you can freeze time? i heard people talk about that you cant because gravity is still acting on it. any thoughts?

What do you make of this article, by physicsworld? http://physicsworld.com/cws/article/news/33256;jsessionid=1CF5E6A097A1B2E8DFDF0BFCC2F917EC It would appear as if they made an artifical black hole in the lab.... Not a gravitational one, but they say that you could make one in an optical fiber, though the method shown is a bit questionable, to say the least.

I was wondering...if matter makes up the universe, planets, life and so forth, then is it believed that anti-matter would exist as a mirror image of this? Or could anti-matter really exist in any form? Do we know? Could anti-matter all exist in one condensed point in the universe as one massive planet or a ridiculously cluttered solar system? Does it follow that the laws of physics, as they apply to matter, would have to apply to anti-matter?

John Stewart in his book "Advanced General Relativity" on page 23 states; "The Lie derivative is the most important and least understood concepts in mathematical physics." I have no idea what he meant by that as the Lie derivative of any tensor density is well know. In fact all tensor densities on a manifold N can be understood not just as twisted sections of various vector bundles but as scalar densities on a larger manifold M (in fact a supermanifold). Thus all we need is the Lie derivative of a scalar density. By definition this is simply [math]L_{X}f = \lim_{\epsilon \rightarrow 0} \frac{\phi^{*}f-f}{\epsilon}[/math] where [math]X \in \mathfrak…

can anyone explain me the basic of String theory

In the quest for reformulating current physics in terms of the information view of modern physics, I pose this reflection. The idea behind the principle of least action, is that a system evolves as per the "trajectory" that minimised the action. In that, there is an implied known relation between the trajectories in general, and the action. So how can one interpret the meaning of this action? One intuitive interpretation is that, the action is simply a measure, defined on the set of possible trajectories, so that it is basically a rating system for trajectories, which is ultimately related to the a priori probability for that trajectory to happen. In that …

From what I understand, producing antimatter would be a very expensive proposition by most means. But if you had a small black hole, and fed it only or mostly with protons, you could get a highly charged black hole. If the black hole were to shed its charge, my guess is that it would do so with the lightest positive particles -- positrons. So would it be possible to throw protons into a black hole and get back energy and positrons via Hawking radiation?

My question is, for a Fusion Power Plant, how would that work? I want to know essentially, dont you have to put in a great deal of energy to get it started in the first place? And, what goes on that makes it produce even more (lots more) thanks

How do we determine the amount of time dilated on our moving galaxy? To measure time dilation we need to measure our speed against the speed of light. Since speed requires a fixed reference point, and everything in the universe is moving releative from one another how do we determine our speed and measure the amount of time dilated? As you know absolute time does not exist, it is all relative and not universal, time in one part of a universe is different from another. The faster our speed through the galaxy against the constancy of light speed the slower our time, but time is perceived as normal. The rate of entropy determines the rate of time dilated. …

The threads on expansion of the universe caused me to take the opportunity to express an interesting reflection that relates to the still open question of the conceptual unification of QM and GR. There two conceptual areas that commonly are discussed, from both philosophical and conceptual viewpoints: 1) Relativity, both special and general, which relate to the concept of geometry and in particular intrinsic geometry. In the general picture of a curved surface, there are two kinds of curvature - extrinsic and intrinsic. The extrinsic curvature relates to how the surface "curves" relative to the higher dimensional embedding space - for example a 2D-surface curv…

Hello everybody. I'm a 2nd year undergraduate in Theoretical Physics, and I have to write a 2000 word essay on an area of physics, or something physics related. I am currently undecided on what to do, and I have 2 weeks left in which to do this work. I have come across the theory of broken symmetry, but do not know much about it, and the article on wikipedia is especially brief. I am considering whter to do my essay on it, but would like to find out more about it first. Does anyone know any good introductory sources? My essay is not required to be especially rigorous, I am just required to have a reasonable grasp of what I am talking about and most of the marks w…

I think some of you may enjoy this: http://www.seb.cc/particles/

Ever since I read about magnetic fields used to contain hot nuclear fusion, it seems like that would be a way to go. It's just that the magnetic field would be so strong, it would interefere the running of the ship, unless the field was produced externally and the rest of the ship was insulated from it.

The 'universe' has two obvious boundary conditions for present time man, vacuum-speed light and 0 kelvin. Does there really exist any one place in our Minkowski world where one may say 0 Kelvin is the temperature here? how accurate would that claim be? macroscopic? microscopic, subatomic? string level? (And sure, a reply on the thread question : the empty space where electrons make their leaps of faith, must of course be 0 Kelvin?) But then I wonder if any part of the space-time 'fabric' or call it empty space (for arguments sake I guess we would say between two neutrinos eh?) actually can have 0 Kelvin... the more intrinsic question is of course if sp…

I saw the other gravity thread but I thought I'd make a new one for this. I have a new idea for the explination of gravity. Basically physical reality is a function of Space-Time. Time consists of Energy + Mass. When there's more mass in an area there's less energy availiable to function as time, or the energy we use to move forward through time. This creates a kind of "low pressure area" in space-time and draws objects towards it as low pressures do. This could also explain the effect of time dillutation around large bodies. What do you think?

Mod note: posts moved/copied from vacuum thread ——————————————— Please tell me about antiphotons or it is just lik ean antiparticle of it.

we`re taught there are 3 types of particles to make up an atom, the Proton Neutron and Electron. but since Neutrons are made of Protons and Electrons as evidenced in the making of a Neutron star and in their Breaking in a Beta decay. aren`t there really only 2 types of particle and not 3? and since Hydrogen is made of 1 of each of these, is that why Hydrogen is probably the most Cosmologically important element?