State Definition and 1000 Threads

Hi all, I was reading Arnold Neumaier's excellent article on the Vacuum Fluctuation Myth, and ran upon one part I have a question about: he notes that "in bare quantum field theory with a cutoff, the vacuum is a complicated multiparticle state depending on the cutoff – though in a way that it...

Homework Statement I have ##C= NK_B (\frac{\epsilon}{K_B T})^{2}e^{\frac{\epsilon}{K_B T}}\frac{1}{(e^{\frac{\epsilon}{K_BT}}+1)^2} ## and need to sketch ##C## vs. ##T## Homework Equations See above The Attempt at a Solution I have ##C= NK_B (\frac{\epsilon}{K_B...

When beryllium donates a pair of electrons to oxygen, that's oxidation, and the metal is Be(II). When carbon and oxygen share 6 electrons, 2 from carbon and 4 from oxygen, this is also oxidation. Of carbon. Even though it got more electrons, and even, I heard, has a negative charge. When...

Hello Forum, The state of a quantum system is indicated by##\Psi## in Dirac notation. Every observable (position, momentum, energy, angular momentum, spin, etc.) corresponds to a linear operator that acts on ##\Psi##.Every operator has its own set of eigenstates which form an orthonormal basis...

Hi My question is not long, but it is very broad; Is nanotechnology simpy just a rebranding of material science? Is there anything else to it? I have not really seen it used outside chemistry and material science. Do simple nanomachinery exist? I guess on a more speculative level it exists...

I'm trying to calculate a Wigner Function of an entangled state, and I'm not quite sure how to proceed. I have created this state by sending in vacuum and a squeezed state into a 50/50 BS, where the output state has a density operator: $$\rho_{34}=S_{3}S_{4}S_{34}|00\rangle_{34}\langle...

Homework Statement Using Hund's rules, find the ground state L, S and J of the following atoms: (a) fluorine, (b) magnesium, and (c) titanium. Homework Equations J = L + S The Attempt at a Solution I'm having trouble understanding what L, S and J mean on a basic level. I read the textbook...

From the path integral approach, we know that ## \displaystyle \langle x,t|x_i,0\rangle \propto \int_{\xi(0)=x_i}^{\xi(t_f)=x} D\xi(t) \ e^{iS[\xi]}##. Now, using ## |x,t\rangle=e^{-iHt}|x,0\rangle ##, ## |y\rangle\equiv |y,0\rangle ## and ## \sum_b |\phi_b\rangle\langle \phi_b|=1 ## where ## \{...

Hello, Im having some issues with my task. 1. Homework Statement The heat generation rate of a cylindrical fuel (D=0.2 m and 1 m long) is 160 kW. The thermal conductivity of the fuel is 100 W/mK and its surface temperature is maintained at 283 K. Determine the temperature at the axis...

Homework Statement I'm currently working on a homework set for my intermediate QM class and for some reason I keep drawing a blank as to what to do on the first problem. I'm given three potentials, V(x), the first is of the form {A+Bexp(-Cx^2)}, the others I'll leave out. I'm asked to draw the...

A popular video I just watched described Fred Hoyle's discovery that the elements of the universe are created in stars. Key to his theorizing was the prediction that fusion would produce of a new state of carbon that had never been observed and which theory predicted would be unstable. Hoyle...

Hi, initially I would like to express that if you look at the first question it asks the rate at which the production goes from up to down, and ıf there is a rate I think the result should include time unit, but when I look at the solution result only consists of numbers ( the multiplication of...

Homework Statement Which cannot be the structure of two acoustic branches, nor three acoustic branches? Simple cubic, FCC, BCC, diamond cubic, NaCl lattice Homework Equations N/A http://solid.fizica.unibuc.ro/cursuri/solid_en/curs_solid_EN.pdf#page=61...

Hi guys! I study Electrical Engineering and, don't-know-why, I don't know anything about state space. Now I'm working on a project where I have a non-linear system. The first task in the project is to separate the linear and the non-linear part of this system, and then obtain the state space...

Hey guys, According to most pop science sources, "before" the Universe started to exist, there were no time, which can be understand easily as time is only possible if there are at least two existing object (e.g. two quarks, two atoms, etc.). Time as I understand it is a measurement of...

Homework Statement A particle of mass ##m## is in a spherically symmetric potential ##V = -\alpha\delta(|r|-a)##. Find the minimum value of ##\alpha## such that there is at least one bound state. Homework Equations ##u = \frac{R}{r}## ##-\frac{\hbar^2}{2m} \frac{d^2u}{dr^2} + \left[V +...

Homework Statement An interaction occurs so that an instantaneous force acts on a particle imparting a momentum ## p_{0} = \hbar k_{0}## to the ground state SHO wave function. Find the probability that the system is still in its ground state. Homework Equations ##\psi _{0} =\left(...

Homework Statement Given ##\psi = AR_{21}[BY_1^1 + BY_1^{-1} + CY_1^0]##, find ##\left<L_z\right>## and ##\left<L^2\right>##. (This is not the beginning of the homework problem, but I know my work is correct up to here. I am not looking for a solution, only an answer as to whether or not my...

The question asks: A physical device can be in three states: A,B,C. The device operates as follows (all time units are in hours): The device spends an exponentially distributed amount of time in stateAA (with mean of 12minutes) and then with probability 0.6 goes to state B, and with...

Hi all, I am reading a book about fundamental quantum mechanics, in which there mentioned many time about the product state ##|a\rangle|b\rangle## of two states ##|a\rangle## and ##|b\rangle## . To my understanding, product state means to combine two small systems to get a bigger one. So I am...

Hey guys, I need some help. Here's my task: Here's what I came up with: I need to calculate prob(x1|z1), prob(x1|z2) and so on and then just write down which has the highest probability. To do that, I would use Bayes rule, but for that, I need p(z1|x1) and p(z1). How do I get these? I have...

I saw another post about this but i didn't quite find what i was looking for there so i thought i'd give it a go instead with a thread. Homework Statement Calculate the exact value of the kinetic energy of the hydrogen atom in its ground state. No more information is given, we are referred to...

Here is the Problem Here is the construction, Hoping that I have done it correct "State with reasons that $\angle$ ACB is bisected by line OC" Many THanks (Party)

What exactly determines a ships ability to withstand extremely high sea states?

As much as I have understood, virtual particles keep appearing and disappearing in a vacuum state. This leads to zero-point energy, Casimir effect etc. Now, I want to know if there is a lifetime (i.e. a time limit) for which these virtual particles can exist before disappearing. Also can there...

Hi, I am a student from the Netherlands in 6V, the year before university, and I'm doing research on Quantum Computing. However, I have difficulty understanding the four states of two entangled qubits, $$\left|00\right> \\ \left|01\right> + \left|10\right> \\ \left|01\right> - \left|10\right>...

Hello! I am a bit confused about the relation between the singlet configuration and symmetry of the system. So in the spin case, for 2, 1/2 particles, the singlet configuration is antisymmetric. But I read that the quarks are always in a singlet configuration, which means that they are symmetric...

Hi, I am a student in the Netherlands, and I'll be attending university next year. However, I am doing some form of research on Quantum Computing with another student for our so-called "profielwerkstuk" but my understanding of Quantum Physics and math is sometimes not at the level that is...

Hi, I was curious to know what the perception of quantum chaos is. It seems a bit on the fringe, but at the same time it seems interesting. An adviser I'm considering working for works on both solid state physics applications and does some theoretical work in quantum chaos, so I'm wondering if...

Suppose there is a test chamber containing liquid nitrogen. The container is insulated and only a small opening is there so that chamber is exposed to atmospheric condition. As the saturation temperature of liquid nitrogen is -196 degree Celsius at 1 atm pressure. chamber will remain at -196...

Hi, As is commonly known, u = u(T,v) h = u(T,p) I've worked with some maths proofs of this a while ago, but do you guys have an intuitive way of understanding this without the maths, that is, why the state function for internal energy is defined by intensive volume and enthalpy with pressure...

I thought this could be explained as follows: a singlet state is one with ##S=0##. Electrons have spin ##\frac{1}{2}## or ##\frac{-1}{2}##, and in the ##1s^2## state there are two electrons. For it to be a triplet state both electrons would have to be spin ##\frac{1}{2}## which isn't allowed, by...

Homework Statement In a coherent state ##|\alpha\rangle##, letting ##P(n)## denote the probability of finding ##n^{\text{th}}## harmomic oscillator state. Show that $$\displaystyle{\langle\hat{n}\rangle \equiv \sum\limits_{n}n\ P(n)=|\alpha|^{2}}$$ Homework Equations The Attempt at a...

Indiana officials are trying to block almost 45,000 black citizens from voting Seems the voter's rights group wants the Justice department to look into this and the local police want to leave it with the local county prosecutors they work with. Either way, Police spokesman Bursten said the...

Homework Statement Estimate the ground state energy (eV) for an exciton in Si. εSi = 12 ε = 1.0359×10−10 Effective masses me* = 0.26me mh* = 0.36me effective mass = 0.15me Values of h 6.626×10−34 J⋅s 4.136×10−15 eV⋅s Values of ħ Units 1.055×10−34 J⋅s 6.582×10−16 eV⋅s Homework Equations E1 =...

Homework Statement A certain molecule has a characteristic rotational energy of 8.81x10-4 eV. What is the energy of the decay photon towards the state with angular momentum quantum number l? Homework Equations E = Erot (L(L+1)) The Attempt at a Solution Why would this not be 12 multiplied by...

I have some confusions, and I would like some help: What states will hydrogen atom be before it emits a photon? Will it possible be superposition of its eigenstates? (If so, then by measuring the energy of photon, we measure its' energy causing its wavefunction collapse, am I right?)...

Homework Statement The spin-orbit interaction in sodium results in fine structure with energy shifts given by: ##\Delta E_j = \frac{C}{2}[j(j+1)-l(l+1)-s(s+1)]## If ##l##, ##s## and ##j## describe the single outer electron in sodium. Show that if this electron is excited to a state where l>0...

Homework Statement Find Vc(0) Homework Equations Nodal Eq , ohms law The Attempt at a Solution Can someone please check my work for Vc(0)? I'll appreciate it.

We know, $$dU=TdS-PdV$$ ##\int PdV## can be calculated if the equation of state is given. I tried to express ##S## as a function of ##P ,V## or ##T## (any two of those). $$dS=\left(\frac{\partial S}{\partial V}\right)_T dV+\left(\frac{\partial S}{\partial T}\right)_V dT$$ $$=\left(\frac{\partial...

[moderator's note: I've decided to allow this question despite the lack of the formatting template - gneill] ladies and gentlemen, my most cordial greeting to you. i write here cause i need a viscosity vs Temperature data table about liquid metals (more specific pure Post-transition metal...

What is the difference between two single-photon Fock states ##|1\rangle |1\rangle## and one two-photon Fock state ##|2\rangle## (all in the same mode)? In both cases the mean photon number is 2. How do we distinguish them experimentally?

According to atty.. entangled system are pure (can be in superposition) while according to Bill.. entangled system are not pure (not in superposition) Here's the prove of what they stated: atty said...

Homework Statement http://imgur.com/a/4YfkJ http://imgur.com/a/4YfkJ Homework Equations for t<0 I understand that Capacitor acts as an open circuit and goes away but why did the 90v and 6ohm resistor disappeared? is it because current doesn't go that way? and also in that KCL at node V1...

I learned about pure state, mixed state, reduce density matrix, etc. from this now famous paper http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf (thanks to Bill) I'd like to know something. Atty said somewhere: "A pure state means that we have prepared many copies of...

Can a beam of light be objectively in a specific photon number state (Fock state), let's say ##|2\rangle##? Or is it (the specification of the state) detector/observer dependent? I.e. we can only say that a beam of light is in a Fock state, but which exactly is detector dependent (detection time...

Let the generators of the SU(2) algebra be ##\tau_{1}##, ##\tau_{2}## and ##\tau_{3}##. Consider an ##N## dimensional representation, which means that the ##\tau_{i}## are ##N \times N## matrices which act on some ##N##-dimensional vector space. Consider the ladder operators...

[FONT=Arial Black]Problem O is the center of the circle and AB is the diameter of this circle , C & D are points on this circle , If $\angle CDB=x^\circ$ ,State the following angles in terms of $x$ $\angle CAB$ $\angle CBA$ [FONT=Arial Black]Workings & what is known $OC=OB=OA$ radii of...

Hello, I want to verify this question. In short, "Where did input matrix Bu arise from?" I was wondering why the state equation has to be in the form of x_dot=Ax+Bu. I got to the point that the highest order terms can be expressed in the form of linear superposition of lower degree terms. If...

Far leftist Jeremy Corbyn won the election for the British Labour Party leadership as expected. He was the incumbent leader since 2015.. He won based on the support of constituent party members, but with almost no support from the parliamentary Labour Party. The party is expected to split...