Constant Definition and 1000 Threads

Suppose I have a self interacting real scalar field ##\phi## with equation of motion ##\partial^i \partial_i \phi + m^2 \phi = -A \phi^2 - B\phi^3##, and I attempt to find constant solutions ##\phi (x,t) = C## for it. The trivial solution is the zero solution ##\phi (x,t) = 0##, but there can...

according to f=GMm/r^2 if force changes based on a distance between 2 objects, so during free fall object is constantly changing its distance, so does that mean the Earth is exerting a non-constant force on that object? if that was right, why's that object accelerate at a constant rate of...

It is said that due to the expansion of the universe, there are some distant galaxies that are moving away from us faster than the speed of light. They can't actually move faster than speed of light itself, because the law of physics over there are supposed to be the same as the law of physics...

Homework Statement Homework EquationsThe Attempt at a Solution [/B] I am having difficulty understanding the question statement . I do not understand how can body come to rest when velocity is directly proportional to time .As time progresses , velocity increases . Could someone help me...

Hello, my questions is not so much homework, but a request for a definition. When we use Cv*dT to solve for dU (internal energy) in a constant pressure example, what is the order of the temperatures entered into dT? Is one to assume its final temp minus initial temp? I ask because it leads to...

If you were in a warp drive spaceship traveling at say 2c. Would all observers see your ship traveling at 2c?

y= 8a³ / x²+4a²

I've run across several instances while doing homework where a question will have two solutions. One will be an equation, and the 2nd will be a constant (usually zero). I can't figure out why this constant is a solution though. For example, take the following differential equation...

I was thinking about the law of conservation of energy, states that energy can neither be created nor destroyed. Then I thought about it more broadly, it actually states that the universe was created with a fixed amount of energy (and this energy only transforms from one form to another) And...

Why is it the case that, in a semiclassical description of the Einstein-Hilbert action, the cosmological constant is small in Planck units? Why does this mean that $$\ell \gg G$$ for ##\Lambda = - 1/\ell^{2}##?

Homework Statement A block of mass M = 10 kg is sitting on the table as shwoin Figure above. There is friction between the block and the table, the coefficient of friction is u = 0.1. The block has initial velocity V, and a constant forceF is applied to the black as showing Figure above. A)...

Homework Statement Homework Equations for equation which has 2 different solutions, D >0 The Attempt at a Solution (1)[/B] D > 0 b^2 - 4ac > 0 3 - 4root2.k > 0 k < 3 / ( 4root 2 ) k < ( 3 root 2 ) /8 has solution of sin tetha and cos tetha sin 0 = 0, cos 0 = 1. when x = 0, and x = 1 -->...

Hello, This is an advanced forces problem from introductory Calculus with Physics. I have mostly solved the problem I am posting here but am just missing a force on my diagram somewhere. M. The jpeg below "MassCartTheProblem_1.jpg" shows a picture of the situation and the goal is to find the...

Hello Friends, I have used in-wheel BLDC motor for my experiment. In this type of motor BLDC motor inbuilt on wheel. This wheel is a part of electric scooter. I wated to find the value of torque constant and back emf constant. Also how to measure torque for a selected current. Please help me...

If Hubble's constant = 160,000 m/sec/million light years and c = 299,792,458 m/sec, then shouldn't any two points in the universe farther than about 1,873,000,000 light years apart be expanding away from each other faster than c? Since light from sources much farther than this has reached us...

You are given an equation and a point. In each case, find the value of the constant a so that the graph of the equation passes through the given point. y = -5x - a; (-4, 1) Solution: Let x = -4 and y = 1 y = -5x - a 1 = -5(-4) - a 1 = 20 - a 1 - 20 = - a -19 = -a -19/-1 = a 19 = a...

In analogy to the fine structure constant, the dimensionless coupling constant of gravity is defined as some reference mass divided by the Planck mass, squared. But what is the reference mass?? I have read thread...

Since force is transformed via: F'x= Fx ; F'y= Fy/ ϒ; F'z=Fz/ ϒ (F' is the force related to the moving frame, F is the force on the rest frame and ϒ=1/√1-v2/c2 ).I expect that G (Gravitational constant) will be transformed between moving and rest frame in order to satisfy force transformation...

Hi. I seem to have forgotten how to implement equality constraints to barrier NLPs and quadratic NLPs. Say for example I have this problem: Max Z = x12 + 2 x22 ST: x12 + x22 ≤ 1 x1+ x2 ≤ 1 The unconstrained problem (quadratic penalty - correct me if I'm wrong) then becomes Z = - x12 - 2 x22...

My question is about the interpretation of the large estimated value. In QM we are supposed to think in terms of measurement results and not of ontological properties. So, if QFT predicts a large vacuum energy what is the correct approach? 1. The predicted value is the result you get if you...

The Lagrangian density for cosmological constant is $${\cal L} = \sqrt{g}\Lambda$$ Let us write, schematically, $$g=\eta+h$$ where ##\eta## is the flat Minkowski metric and ##h## is the spin-2 field. Expanding the square root for small ##h## we get something like $${\cal L} = \Lambda + h\Lambda...

Homework Statement The aim of a laboratory course was to measure the x-ray fluorescene spectra of 20 metallic samples. By comparison of the peaks in the energy spectra with known electronic transitions (e.g. ##K_α## of ##Cu##) the materials were identified. After that, Moseley's law $$...

It's not a homework question. I just thought up a method of finding answers to problems where a number is raised to a complex number and I need to know if I am right. If we have to find e^(i), can we do it by; first squaring it to get, e^(-1) which is 1/e and then taking its square root to get...

If you are stationary say 10m below the ocean surface does the water pressure at your location vary with the waves. For example: When a wave crest is above you than means perhaps 12m of water is above you. Then a few seconds later a trough is above you so only 8m of water is above you. So you...

Som news outlets are reporting a potential solution to the cosmological constant problem: https://arxiv.org/pdf/1703.00543.pdf opinions on this paper are much appreciated.

Is the Hubble constant decreasing over cosmological timescales?

Hi all! How is humidity related to temperature in a system where temperature is constant in time but not in space? As an example: If we have humid air trapped between two parallel walls with T1 and T2 respectively, how does humidity behave along the line from one to the other wall? Is absolute...

I have heard that the probability of an unstable nucleus decaying is always constant. Is there any way to change this probability?

What's the difference between activity of a radioactive sample and the decay constant. Both are measured in second inverse. Please distinguish among the two?

Homework Statement Hi, I recently performed a lab experiment for calculating the moment of inertia and spring constant of a couple of equal masses on a steel rod. I had to do this experiment at the exact same time as performing another experiment so I was unable to perform any calculations in...

Hello! I encountered in a problem the terms heat capacity at constant volume and density (##n##) and heat capacity at constant chemical potential (##\mu##) and volume and I need to prove a relation between them. What is their definition? I thought that for the first one it would be...

please explain the concept of dielectric constant in the simplest CHEMICAL terms possible. why does it decrease when the temperature increases? and why does it increase when the polarity increases? please keep it simple and brief.

Homework Statement A box is sliding with constant acceleration a to the right. Inside the box there is a quarter of a circle upon which a frictionless ring can slide. Find the angle theta in terms of the other given variables. Picture in solution Homework Equations F=ma, etc. basic stuff...

I have built a torsion wheel catapult (Mangonel) for an assignment,and I need to do some theoretical calculations about the displacement, velocity and time of the projectile, the problem is I don't know how to calculate the spring constant without the displacement of the spring (x) and i don't...

Consider the dependence of entropy and of temperature on the reduced Planck's constant (taken from page 23 of Thomas Hartman's lecture notes(http://www.hartmanhep.net/topics2015/) on Quantum Gravity): $$S \propto \hbar, \qquad \qquad T \propto \hbar.$$ I do not quite see how entropy can depend...

Could someone provide a good explanation as to why light's frequency doesn't change under refraction? The textbook I'm using gave us a two step derivation and I don't really feel like it did a proper job in explaining anything (it's Haliday). Also, a slightly *crackpot* follow up question -...

If Planck's constant is changing, how slowly would it need to change before we could observe that something was going on? And if changes were discrete, how large quanta would it take? (for us to observe the jumps) And a follow-up question: If there was another universe here, running a different...

Hi, we know that the speed varies inversely with the torque. The more the torque, the lower the speed. From torque-speed curve, we can calculate the slope. When the applied voltage increases, the straight line shifts upward while when the voltage decreases, the straight line shifts down. How...

I'm trying to solve one of the problems in my textbook (Atkins Physical Chemistry) and I just can't get it out. Here's the problem: "The data below apply to the formation of urea from ammonium cyanate. Initially 22.9g of ammonium cyanate was dissolved in enough water to prepare 1.00 dm3 of...

If the Earth were divided into 4 sections and separated far enough that they have no gravitational pull on each other, would the gravity on each section be 25% of the current gravity on Earth?

Hello everyone, this is my first post, so go easy on me! Thank you to those who are able to help. 1. Homework Statement The problem is taken from Professor Shankar's Fundamentals of Physics exercises (Problem 3). Romeo is at x = 0 m at t = 0 s when he sees Juliet at x = 6 m Romeo begins...

Homework Statement Suppose there is an object that is a distance ##r_0## from the center of a planet that is nearby (the object is outside the surface of the planet). Let ## r ## represent the distance from the object to the planet's center. Let ## t ## represent time. The object, which is...

The speed of light is constant, in what ever direction, that's not disputed. Now in relativity that as I understand light speed constant C is bound up with time, eg faster you go faster time pass for an outside observer but stays the same in your field of reference. Or to put it another way the...

The dielectric constant of water is 80, however its refractive index is 1 ·33 invalidating the expression n*n=ε. why?

Hi, I am building a charger for my bicycle front and tail light that uses dynamo to charge them while cycling. However, depending on my speed, current is fed differently to lights and they start to flicker. Therefore, I was wandering if there is a way to make a constant current source which...

Hello everyone! I've been curious about this for a while and couldn't come to a conclusion on my own so I've decided to ask it here. I'm wondering if it's possible for a function, f(x), to have a rule which would allow it and it's derivative to both approach a constant value as x approaches...

Solve for all real number t values. sqrt {2t + 5} - sqrt {8t + 25} + sqrt {2t + 8} = 0 I see there are no constants in this problem. I typically isolate the radical on one side of the equation and the constant (s) on the other side but there are 3 radicals on the left side. This is strange...

I'm confused on why the dry air gas constant varies: Dry Air Gas Constant of 286.9 from The Engineering Toolbox Dry Air Gas Constant of 287.22 from https://www.physicsforums.com/ttp://www.peacesoftware.de/einigewerte/luft_e.html Dry Air Gas Constant of 287.05 from Brisbane Hot Air Ballooning...

Could einstein's theory be completely wrong if we discovered that the speed of light is different in an another galaxy ( speed light isn't constant) and if we proven that there is particles or objects which moves faster than light by 100 or 1000 times?

The Yang-MIlls Lagrangian is given by ##\mathcal{L}_{\text{gauge}} = F_{\mu\nu}^{a}F^{\mu\nu a} + j_{\mu}^{a}A^{\mu a}.## We can rescale ##A_{\mu}^{a} \to \frac{1}{g}A_{\mu}^{a}## and then we have ##\frac{1}{g^{2}}F_{\mu\nu}^{a}F^{\mu\nu a}.## How does the second term change? Does the...