Physical Definition and 1000 Threads

We (company I am interning for) are meeting with various suppliers in efforts to find a new source of vacuum pumps for our brake boosters. We are looking to make a switch to an electrical pump versus the mechanically-driven pump we used previously. One of the issues we are having with this is...

As I listen to lectures trying to explain the universe based on the laws of physics, it makes no sense and it can be all over the place with holes and gaps. Dark this or a catastrophe here.So the physical laws seem to be lacking when it comes to explaining the nature of reality. We can use these...

Searching for a book similar to V N lange physical paradoxes and sophisms by mir publishers please don't recommend books that involve numerical question , please suggest books that have interesting curious question and paradoxes on theory of classical mechanics books similar to above mentioned...

I was and am reading quite a lot of books on GR and QFT and there's the distinction between a physical state and an unphysical state. What is the difference? What makes a state physical? I know this is a bit philosophical . Doesn't this distinction change with time and experiments?

So, all of the generators of the Poincare group are associated with pretty well-known physical quantities. Time translation is associated with energy, space translations with momentum, rotations with angular momentum, and boosts... well, boosts are generated by the "generators of boosts". Do...

Does the fictional substance ice-nine in Kurt Vonnegut's Cats Cradle violate any physical laws, or is it merely something that does not exit?

Gonna preface by saying I never thought linear algebra would be a class I would regret not taking so much... but in short the goal is to reduce an arbitrary symmetric NxN system using a set of auxiliary constraint relationships, e.g. for a 3x3 \begin{bmatrix} V_1\\ V_2\\ V_3\\ \end{bmatrix} =...

Good afternoon everyone! I've learned that thermal conductivity has a form of second-rank tensor. As you know, diagonal components of stress tensor mean normal stress and other components mean shear stress and like that do off-diagonal components of thermal conductivity tensor have some special...

I am having trouble to understand what it means by "physically relevant real parameters" and how does it help us to specify a quantum system. Let say, we have a state of k half spin electrons? My guess is about the local phase of the spin, and this would make it 2^k parameters since each...

Here are the quotes https://www.symmetrymagazine.org/article/show-your-affection-with-physics-valentines , I find them funny except for the last one is hurtful, I shouldn't say such a thing for someone on a valentine's day because they would care about the valentine's day, personally I find it...

I am [working][1] on the algebra of "divergencies", that is, infinite integrals, series and germs. So, I decided to construct something similar to determinant of a matrix of these entities. $$\det w=\exp(\operatorname{reg }\ln w)$$ which is analogous to how determinant of a matrix can be...

The Vacuum Permittivity of the classical vacuum seems to be for just conversion of units in Coulomb's Law, like Coulomb's Constant in disguise. Does the Electrical Permittivity of the Vacuum in classical electromagnetism have any real physical significance other than in the above context...

I am studying Quantum physics and I'm having some problems to understand what is the Wave Amplitude since I can't find a physical significance to it. Does anyone ever heard something that come close to a physical significance?

I would like to get a more physical interpretation of conduction electrons (fermi gas) in a metal. I imagine ionized valence electrons close to the ions, with the fermi level (highest energy electrons) of the gas participating in conduction. A point of confusion for me...the first ionization...

Hello, In non-relativistic physics (where things move slower than the speed of light), the following physical quantities are invariant and variant (or relative) i.e. vary in value depending on the chosen frame of reference: Variant quantities: time ##t##, velocity ##v##, momentum ##p##...

Hi everyone! Can someone explain which are the differences between a physical node and a virtual one and which one is potentially better . I've been looking for information but I haven't found anything. Thank you a lot.

$$cos\theta = \frac {s}{1-s} = \frac{p-1}{p}$$ in this equation ##\theta## is the bond angle and ##s## and ##p## are the fractional s-character of the orbital and p-character of the orbital. This is equation is used rigorously in showing that the s-character of the axial orbitals in a ##sp^3d##...

I need to find some more good podcasts about the physical sciences. Searching the interwebs gives lots of popular general science stuff like Science Friday, Sean Carroll, and Neil DeGrasse-Tyson; those are ok, but I want stuff aimed for people that know calculus, if you get my drift. So what...

As in, is it a physical quantity/parameter like mass or is it a descriptive name that we give to the flow of dynamic processes? This is not a theory or idea, just a question that I feel compelled to ask after reading an article that claims that a study shows that time travel would be possible...

If someone were to talk about "a non-physical energy source" would you consider that a contradiction in terms?

Hello, I've always heard that the choice of signature for the metric was just a matter of convention, i.e. taking (+---) or (-+++) had no physical impact. The groups O(1,3) and O(3,1) being isomorphic it made sense to me. However, I came across an article discussing the Pin(1,3) and Pin(3,1)...

Summary:: I have two substances H2O and CH3OH given at a temperature T and pressure P. I also have critical temperatures and pressures. How can I find the physical states of these substances. My teacher recommended me to use the Antoine equation and find the saturation pressure, but I can't...

When I think of a wave propagating through space I think of a geometric wave-like structure propagating through the matter in the surrounding environment. If someone yells and you hear their voice is it actual matter that is emitted and that your ears pick up on? If this were the case there...

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I recall my memory when I was a high school student. I first learned about energy from Newton Mechanics. The only forms of energy involved are kinetic energy and potential energy. At that time, energy is more like a mathematical shortcut derived from F = ma rather than a concrete physical...

I've been reading about the Holographic Principle, and this concept of information in physics came up. The idea that physical particles and interactions can be described in bits. But, how exactly would those bits work? Is this even a meaningful question? Could someone provide a concrete...

In some experiments of a complex physical mathematical system, we found some symmetry phenomenon, very similar as symmetry breaking phenomenon, say, as translatable sysmmetry etc. These symmetry (breaking) phenomenon occurs in most of the parts of the system or some parts of the system. Can you...

What should a PI look for in a physical sciences PhD candidate when hiring? Among diligence, knowledge about the field and cleverness, willingness to follow their boss, complementary skillsets if they are from another discipline, what's your favorite? What else?

(sorry i post this here now because i didn't know about this sub forum earlier) I came across an interesting paper from which I'll quote parts of the intro: and the conclusion: obviously the authors are more competent in Physics than I am - so are most PF member. what are your opinions on...

I came across an interesting paper from which I'll quote parts of the intro: and the conclusion: obviously the authors are more competent in Physics than I am - so are most PF member. what are your opinions on this? can the work of these authors "discover" physical laws in any way or is the...

Hi, I have a question regarding Phonons and daily experience: Let's say I have a table and I hit it, does it mean Phonons were created where I've hit on the table? Meaning: By hitting the table, I'm giving energy to it, this energy goes to the motion of the table atoms, and this motion of the...

Sure it seems like an impossible feat but I need to gain a bit more depth, every little helps. I've been trying to analyse different things in life. Behaviours of other individuals', my own behaviour, our interaction with other conscious individuals, e.t.c. Essentially I've just been trying to...

There is a paper here: https://www.mdpi.com/1099-4300/19/5/188 And a lengthy article here: https://www.quantamagazine.org/a-theory-of-reality-as-more-than-the-sum-of-its-parts-20170601/ The general argument concerns causal emergence and whether all causal agency arises directly from the micro...

A quantity ##p## can be expressed as the product of a dimensionless number, ##\lambda_p##, and a unit, ##u_X##:$$p = \lambda_p u_X$$When we write the equation of a physical law, do the symbols represent the physical quantities ##p## or their dimensionless coefficients ##\lambda_p##? That is to...

How was supersymmetry discovered? 13:00 And what were the original motivations for it? Is there some kind of intuitive way to look at and work with the formulas? For instance, in the theory of differential forms, the scalar product of two 1-forms U and V is *(U ∧ *V) = UiVi. It is useful to...

Hello Everyone in the forum: I have a theoretical question about Worm Holes. So for the sake of this question let's just assume we have the technology and the power source to fire up a small human size worm hole. My question would be regarding the edge of the worm hole. Would you be able to...

As some simple Lie groups and their algebras are essential for our current understanding of QM, I wondered if especially the highest positive (or likewise lowest negative) root can be explained physically. The roots are the weights of the adjoint representation. Are their physical meanings...

On p. 246 in the Peskin QFT textbook, below is stated where Z3 is defined as the residue of the q2 = 0 pole, explicitly as $$Z_3=\frac{1}{1-\Pi(0)}$$ and e is the bare charge. In advance, the exact photon two point function is calculated as $$\frac{-ig_{\mu\nu}}{q^2(1-\Pi(q^2))}$$ Though...

For example, talking about density formula; it conveys the essence that if a container with volume"V" can hold "m" mass of substance then " d" will be the density. Jumping on to frictional force formula "Ff = μN", how do I know the physical meaning of the coefficient of friction from the equation?

As we all know that division simply means how many parts of the whole we have (or splitting into equal parts) 1)Example:- if we have 12 apples and there are 3 people so each will get 4 apples right. Easy! Now my question is how does this definition makes sense in term of physical quantities ...

I am really struggling with these problems and do not really know where to begin. In most cases I have just defined what the modelling means, e.g A rough surface is one upon which friction acts etc. I would really appreciate some help with suitably answering these questions comprehensively, and...

In derivations of capacitance it is standard to consider two oppositely charged, infinitely thin sheets. If we construct a Gaussian cylinder across one sheet, we obtain ##E_{1} = \frac{\sigma}{2\epsilon_{0}}## for one sheet, and then we can superpose this field with that from the other at an...

Hi, The following is not a homework question. My question is: My answer is: Total pages required = 2^32/2^7 = 2^25 pages Thus page table has 2^25 entries PM = 2^16 Total page frames in PM = 2^16/2^ 7= 9 page frames Somebody please guide me what is the correct solution for the above. Zulfi.

Hey all! I am trying to understand the terms in the source-side of the k-epsilon transport equations. My only reference on this so far has been the wikipedia article (in my defense, it's not in Landau! the gospel has forsaken me :cry:). If you have a reference that goes into gory detail on the...

Is there a way to broadcast emergency messages via cable radio? Its not really radio but audio going out from copper or fiber using existing landlines or CATV cables. No tuner needed, could just be a speaker. The system I am looking for does not need internet or mobile connections. I imagine it...

Hi all, Just a clarification question as I'm learning. It's possible to have Feynman diagrams where the internal lines (virtual particles) are in fact on shell. 'On shell' would imply 'observable,' (maybe?) but as noted in @A. Neumaier's great FAQ, only sets of Feynman diagrams have predictive...

Consult a physical problem that USES piston to absorb water: Pistons with surface areas S1, S2 and S are placed horizontally at the same height (H). S1 = S2 S=S1+S2 When F starts moving to the left, how do you calculate its force? Is F=ρgHS? (*The friction force doesn't have to be calculated.)

I can see why it would be pretty illogical to speculate that physical constants change over time, but is there more to it than just being 'illogical' to assume otherwise? Is it axiomatic in physics to presume certain physical constants are constant, because otherwise stuff like atoms and things...

In particular I'm studying the paper "Theory of dynamic response functions of periodically modulated physical systems" by Lovesey et al. and "modulated system" are mentioned many times. My thesis advisor recommend to me reed this paper but is very confuse, any reference you can give me in...

I know I have to use λ=xd/L. But I don't know what any of those variables (except lambda) mean. If you assume that 0.59 is x times d, you can get an answer that is close. 0.59/100 = 5.9*10^-3. Can someone explain the solution and meanings of variables using a diagram? (The answer to the...