Physical Definition and 1000 Threads

In some class notes I found those conditions interpreted as a "five requirements on Hamiltonian of physical system": 1. Unitarity -> Hamiltonian has to be hermitian operator 2. Claster decomposition (microcausality and locality) -> (? missing part) 3. Poincare invariance -> Hamiltonian...

Out of many properties polymer scientists are interested to calculate one of the most common is "Rg" i.e. Radius of Gyration. Can anyone put more light on the physical significance of this value? Can Rg value of two polymers be compared? If yes what conclusion can be drawn from such comparison?

How can I see that the generators of the Galilean group correspond to energy, momentum, etc.? References which cover the Galilean group and algebra as well as their realization in phase space are appreciated, especially if they are not too sophisticated. Thanks kith

Is there anything in the physical world that is actually random even after we were given every single bit of information needed to calculate an outcome? Rolling a die or flipping a coin doesn't count, because if we did all the calculations, we would be able to calculate what the outcome would...

I wonder what really happens to powers in capacitors and inductors when they are connected in a circuit either in series or in parallel. I know that inductors have a positive reactive power while capacitors a negative one, so I imagine inductors release energy while capacitors absorb it, but it...

I've always found it pretty amazing that human beings can understand the rules that govern the universe we live in, but is there a fundamental reason as to why they are comprehensible at all? Do they have to be rooted in logic? If it's just something that is unknown, that's a perfectly...

If a sugar cube size piece of neutron star weighs as much as every vehicle in U.S.A, and H2 in the core of Jupiter has been compressed to a metalic version of itself, what then is the limit of compression? Can matter be compressed further than that of a neutron star?

Could we harness energy from Earth movement relative to physical vacuum? Earth is moving around Sun with speed of 30 km/sec. Also there exist force of Casimir and similar effects. If we have some body (for example a ball) which is moving in some media (for example water) then to harness...

Hi I was just wondering what ways you can smash glass without physically touching/breaking/throwing something at it. For example, I know that the "force" of an explosion can break glass that is a fair distance away from the actual explosion. So is there any way you could make something that...

Hello, Given the hamiltonian : H = -( aS_z^2 + b(S_+^2 +S_-^2) ) with S=1 and a,b>0 are constants. working with the base: { |m=1> , |m=-1> , |m=0> } The matrix form of H is: H = \left( \begin{array}{ccc} -ah^2 & -bh^2 & 0 \\ -bh^2 & -ah^2 & 0 \\ 0 & 0 & 0 \end{array}...

Hi all, I'm trying to understand exactly what the physical meaning of conductivity/current is in relation to waves. if we have a wave traveling through a conductor, we find that it decays exponentially, i.e. e^{-\alpha z} where \alpha=imag(k)=\omega\sqrt{\frac{\epsilon\mu}{2}}...

By "physical particle" I mean color-singlet particles which have asymptotic T=\pm \infty states. How many stable particles exist in the theory? Only one? SU(2), SU(3), and SU(N) gauge groups can all be discussed.

I have seen PeterDonis state that predictions of GR are expressed as contracted tensors i.e. scalars. And they are coordinate independent. So I have a question what these scalars represent physically? Could it be that they represent measurements of physical quantities (with tensors dual...

I try to get the gist of the Special and General theories of relativity for more than two years now. And I still don't understand if the geometrical explanation really explains or just describes what is physically going on when talking about all the relativistic effects (like gravitation, time...

Hi guys. Sorry if this is in the wrong topic, but what is the physical size of an electron? I understand it can sometimes behave as a wave. But when it is a particle, just how big small is that particle?

Does anyone know what the physical property measured in seismic surveys is? Seismic surveys used in searching for hydrocarbons to be more specific. I was thinking it would be the rocks density but I'm not sure, can anyone help please? :)

Homework Statement The physical pendulum shown on your paper is a 27.0 kg wedge of a circular disk of uniform density with radius, R=1.87 m and opening angle β=0.847 radians. The pivot point of the pendulum can be moved along the center line of the wedge as shown on your paper...

Dear friends In quantum mechanics what is the physical significance of normalizing a wave function? Thanks in well advance

Go easy, not an expert. My intuition tells me that the maximum possible entropy in a given space is going to coincide with the arrangement requiring the most information to describe it. Let me know if this is wrong. Ok, so now what I want to know is what an actual arrangement like this...

Hello. I'm trying to understand why, in terms of Maxwell's Equations, the ratio of the number of turns in a transformer converts an input voltage to an output voltage. EE explanations only seem to go as deep as this article: http://en.wikipedia.org/wiki/Transformer#Basic_principles They state...

I can now although do the maths related to plane stress etc but I have struggled to grasp the logic behind this concept. It says changing the way you see the stress by rotating the view, stress changes. My question is why ? Why is this so that we see stress with one value when standing at let's...

Thought experiment: Say for instance that a Baseball game is being played out on a planet that is orbiting the outer edge of a black hole. You, from deep in space away from any gravitational source, are watching this game from a powerful telescope. The batter comes up to bat; the pitcher...

If ρ is the desity operator of a ensemble. We get (ih/2π) ∂ρ/∂ t = [H,ρ ]. for a stationary state [H,ρ ]=0 . So H and ρ can share the same eigenvectors. Can someone explain what does this mean? :smile:

I understand the basics of the mathematical descriptions of systems in superposition. But what I'm not clear about is whether such a system is actually in more than one state at the same time. Is this a matter of QM interpretation or is it simply moot b/c we can make no measurements that can...

I'm currently enrolled in precalculus and I'm finding that almost everything we've learned so far is just Algebra 2 review. I've been looking for a book where I can self study Calculus and move ahead, and I stumbled upon Calculus: an intuitive and physical approach by Morris Kline. I am...

Homework Statement Estimate ΔG for the process where one mol of ideal gas is subjected to an increase in pressure from 1.00 atm to 11.0 atm at 25.0°C. Homework Equations ΔG=ΔH-TΔS ΔH=C(p,m)(Tf-Ti The Attempt at a Solution Seems straight forward, but it seems i am not given...

Hi, I'm trying to simulate the ship traveling in ice. Basically, I would like to assume that the rigid body dynamics is sufficient to do the job since the main point here is the interactions between rigid ice fragments and the rigid ship. The fluid interactions with ice fragments should be...

Sorry for the confusing title! I have a question that I cannot wrap my mind around... Suppose the universe attains its state of maximum entopy (assuming maximum here also involves quantum effects such that in the end even the atoms disintegrate into photons and leptons). I understand that in...

The Feynman slash \slashed{a}=\gamma^\mu a_\mu maps a four-vector a to its Clifford algebra-representation. This is a linear combination of the gamma matrices with the components of a acting as expansion coefficients. What physical significance does this new object have? The gamma...

A phase factor is e^{i\phi}. Mathematically a multiplication of a wavefunction by phase factor is equivalent to a rotation of the state vector by the angle \phi, however the probability amplitudes are unchanged. So what is the physical meaning of it?

Hello, I am a chemist and have been working on chemical dynamics. Recently I have started working on some many body interactions. Therein I have found some ideas about Fock Space, Fock Matrix, Fock Space Coherences. These are extensively used to provide characteristic information in...

I googled this and surprisingly no one seems to have an answer. What would have to be done to the water to make it change chemically?

I'm not sure if this belongs here or in the physics section. The mathematical definition of curvature is the derivative of the unit tangent vector normalized to the arc length: \kappa = \frac{dT}{ds}. If we apply this to a parabola with equation y = x^{2} we get \frac{2}{(1+4x^{2})^{3/2}}...

I am using ifftshift function in matlab, mathematically it does the following functions If M is a row matrix: M = 1 2 3 4 5 6 7 8; then ifftshift(M) = 5 6 7 8 1 2 3 4, i.e. it replaces first half with the second half. Although how can be explain this function physically?

Homework Statement A physical pendulum is made of a uniform disk of mass M and radius R suspended from a rod of negligible mass. The distance from the pivot to the center of the disk is l. What value of l makes the period a minimum? Homework Equations The Attempt at a Solution

Hi, I some basic questions on the physical meaning of bra-ket notation. I have looked at a lot of material, and I have seen descriptions of the algebraic properties of bra-kets, and I have seen hints at it having meaning regarding the probability of events happening/state changes, but I can't...

I've been looking at the various Planck units, and I'm wondering how they are constructed from the constants involved. Like is there any physical reasoning behind those equations? I've looked all over the place for derivations of the equations or what the actual physical meaning of the units...

Hello, Just wondered what the correct way is to display physical units on chart axes. Let's say for example thermal resistance of a heatsink extrusion is plotted as a function of length, and so the units for the y-axis are K.W-1 My 'A' Level physics teacher always insisted on (in order...

Hi. So if you have \frac{d p_{\alpha}}{ds} = \frac{q}{c} F^{\alpha \beta} u_{\beta} how could you possibly go on proving this its form is invariant under all coordinate transformations? Or any physical law of any form, really? I guess my point is how do you represent "all possible...

Need a physical picture! The electric potential of some charge configuration is given by V(r) = A*e^(-λr) / r Its Electric field is E = A*[(λr+1)/(r^2)]*e^(-λr) \hat{r} And its charge density is ρ = 4*pi*A*ε0*δ(r) - [(ε0*(λ^2)*A*e^-λr) / r] , where δ(r) is delta function. The thing that...

I'm trying to understand the Heisenberg Uncertainty Principle, as it relates to experimental measurements, because it's kind of confusing me. We just learned the derivations for it in my QM class -- basically it's two standard deviations multiplied together (corresponding to measurements of...

Does anyone have a solutions manual for the biophysics textbook, Physical Biology of the Cell. Or a link/login info for an online copy?

What is the physical (i.e. molecular/chemical) difference between a normal star and a Cepheid Variable? Do we know and if so can we explain what gives rise to the specific period-luminosity tie? Thank you.

I've been searching for a good book on Calculus that is great for self-study, and at the same time, walks the reader through the WHY behind the math. I am farely upset at how today's educational institutions teach math as plug-n-chug subject without walking the students through the underlying...

Can someone give a physical meaning for imaginary numbers? The imaginary numbers, in my opinion, are truly imaginary. What do they even represent? Irrational numbers are, well, preposterous but I can accept them. √2, π and φ have some tangible meaning, but √(-1)? What does it mean? A solution...

Can all formulas be thought of intuitively/physically? For example, average speed is change in distance over change in time, that is intuitive and can easily be derived But when you have something like v^2 = u^2 + 2ax, or e=mc^2, how do you think of it intuitively? Specifically the squared...

It is an old idea that, at least in principle, hidden variables could be local if they are superdeterministic. However, so far this idea seemed too speculative for highly respectable journals such as Physical Review Letters to publish research on it. But now it seems that it has changed. The...

Homework Statement The distance between crystal planes in a KCl crystal is about 3.14 \times 10 ^{-10}m. Calculate the Bragg's reflexion angle of first order for electrons with kinetic energy of 4keV. Compare it with photons that have the same energy.Homework Equations \lambda n =2d \sin...

Mathematical Methods in the Physical Sciences (3rd edition) by Mary .L. Boas, Does this book has separate solution manual?

Dear all, is the relation between chemical composition of a material and its physical properties a peering relation or a relation of subordination？