Spontaneous Definition and 154 Threads

Hi.. Does the Einstein's coefficient for spontaneous emission B depend upon the energy difference between the two levels?

Hey, everyone. This is my first post. I am a physics and science lover with little university level schooling in those fields. I was reading the new hawking/mlodinow book "The grand design",a nd had a question about the spontaneous creation on the quantum level. The book states that...

At certain concentrations of energy, there is the possibility of particles with mass forming. How does one measure "concentration of energy": by the wavelength? Or energy density? At what concentration will this occur, and why?

Interesting paper: http://arxiv.org/abs/1009.1136v1 The Small Scale Structure of Spacetime Steven Carlip (Submitted on 6 Sep 2010) Abstract: Several lines of evidence hint that quantum gravity at very small distances may be effectively two-dimensional. I summarize the evidence for such...

Okay, I've heard that in Stephen Hawking's new book, The Grand Design, he claims that the law gravity somehow created the universe from nothing. Can any of you give me a conceptual understanding of how this could occur?

"Spontaneous" reactions require activation energy? To my understanding reactions are considered "spontaenous" if they require no additional energy for the reaction to occur. However, they require activation energy. Why is activation energy not considered "additional energy?" The term...

1. If you walk along the top of a fence, why does holding your arms out help you to keep your balance? 2. Charge is also said to be conserved. What does it mean? Explain. 3. When a car drives off a cliff, why does it rotate forward as it falls? 4. Why does a book sitting on...

The reaction between 2KOH + H2SO4 -> K2SO4 + 2H2O is exothermic... However is this reaction spontaneous as well? If so then why? the concentration that i used was: KOH - 2M H2SO4 - 1M (I writting a lab report on the "course of this reaction"...spontaniety of the reaction is a...

Hello, If a reaction is spontaneous when calculated using Gibb's Free Energy formula, Delta G = Delta H - (T*Delta S) Does it mean the reaction will occur at impossible temperatures even (such as 999999999999999999999999 degrees Kelvin) for ex: H2O(g) C(s) --> CO(g)+H2(g) Delta H =...

okay, so pairs of particles can be created spontaneously out of nothing (from ZPE?), and then within the time allowed by HUP, recombine and annihilate each other. correct so far? if they do not recombine, they each become real particles, (does that mean we have stolen energy from nowhere?)...

In Weinberg's book, Quantum theory of fields-II, he talks about a chair in the chapter on spontaneous symmetry breaking. He says that, for a chair, a state with a definite l value is not stable but a state with a definite orientation is. I do not understand what he means. An l state can...

Hey all, I am just wondering if one can directly calculate the Einstein coefficient in spontaneous emission of, say, two-level atoms through feynman diagrams? I searched for sources in google but could not find anything. Thanks a lot for an answer! Wit best regards, blue2script

Homework Statement Find whether the following is spontaneous. Forward= (process as written), backwards, both or none Homework Equations 1. water & syrup mixed to give a flavoured drink 2. Piece of paer at room temp react with O2 to give CO2 and H2O 3. Bathtub water gets cold after you...

Is spontaneous atomic disintegration possible under current knowledge? I mean hypothetically if we could isolate one hydrogen atom in a container how long it would be hydrogen atom? Thanks!

Book: Maggiore-A modern Introduction to QFT Section:11.1 He says that if a symmetry transformation multiplies the vacuum state by a constant phase factor only, the symmetry is not broken.. Section:11.2 U(1) symmetry is spontaneously broken...multiplication by exp(i theta) takes the...

I'm interested in generating entangled photons from barium borate but have a few questions: 1) Taking one of the virgin entangled photons- before any measurements - does it have a random polarization? Ie, if I put any polarizer in its path will 50% of photons make it through? 2) I know...

Hi all, I'm doing a project that includes an hydrogen 2s->1s decay and I need the full derivation of this process, so if anyone can recommend about a book it would be great. I first thought it should be easy to find but to tell you the truth I have looked and found scratch. 10x a lot...

I was doing some research on Technetium and I found out that it occurs naturally in uraninite from the spontaneous fission of U-238. But on the decay chain of U-238 I can't find Tc any where... So what's the difference between spontaneous fission and radioactive decay?

Hello everyone, I'm a bit confused by something I've read as have been unable to find resources to clarify it. Here is the statement that confused me, from Binetruy's Supersymmetry textbook (p.26): It is well-known that [in the case of ordinary continuous symmetries] no possibility of...

Are spontaneous and stimulated emission selected by a Boltzmann's statistics ? Consider 2 levels(m,n) oscillators in thermal equilibrium with Einstein's coefficients Amn (spontaneous emission), Bmn (stimulated emission), Bnm (absorption) and r(f) the energy density at the frequency f (black...

hello all gauge symmetries are redundencies of the description of a situation. Therefore they are not real symmetries. So in what sense does it mean to spontaneously break a gauge symmetry? ian

Homework Statement What is the reducing agent in the following spontaneous reaction? OCl-(aq) + I2(s) + 2 OH-(aq) ---> Cl-(aq) + 2 OI-(aq) + H2O(l) Homework Equations The reducing agent is oxidized in the process so it loses electrons. The Attempt at a Solution Both I2...

is such a thing possible? I am curious to know if this could/does exist. An alternative would be if someone gave an example of a reaction where electron capture occurs and the product ends up being stable enough to not decay into anything further. Thanks (btw, does cold fission exist...

This question concerns a problem in Arfken and Weber (from the infinite series chapter, after the power series section). I went to the homework section, and the titles beneath each section specifically imply that a question from a graduate book is inappropriate for that section. I thus post it...

Is it possible to describe spontaneous breaking of the local gauge symmetry in the standard Hamiltonian formalism, without any manual redefinition of the gauge field( A(r) -> A(r)+▽Λ(r) )? Detailed description of my question is given below.(Quite lengthy.. sorry.) 1. By the 'standard...

Hi: What is Spontaneous symmetry breking ? and when does it happen.? Regards

Was the early spontaneous symmetry breaking caused by exponential expansion in the first instant of standard theory? Is that the reason that the early Big Bang universe is thought to have contained equal amounts of matter and anti-matter (produced by spontaneous symmetry breaking)? Does...

On spontaneous symmetry breaking and Higgs’s mechanism of mass production From lectures: L. Peak and K. Varvell. The Physics of the Standard Model. Full Lagrangian for fermion and photon Combine the gauge-invariant Lagrangian density describing a fermion field in the presence of an...

If a reaction is not spontaneous is there any way of making that reaction occur? Question Details: We know that del G=del H - T(del S) if del H is positive and del S is negative then del G is always positive. There is no way of making del G negative. My question is whether such a reaction...

How can you tell if a reaction is spontaneous?

Could someone please explain why relatively light nuclei do not undergo spontaneous fission? Thanks.

Hi everyone, I'm puzzled by this phenomenon - when there's a thin sheet of water flowing in the street, it forms little wavefronts which appear periodic. Obviously the water gets thin enough to interact with the rough asphalt surface, but how does the random texture manifest an organized...

As we know the spontaneous fission of an odd nucleus to an 2 odd nuclei happens with high probability when (Z^2)/A is greater than or equals 45 The conclusion of this is attached in pdf file with the post using the liquid drop nucleus model to explain the problem The question is here now...

As we know, if we have a group of atoms at a moment N(t) in an exited state, it will exponentially decrease according to the relation: N(t)=N(0) exp(-At)=N(0) exp(-t/(tau)) Where A is the Einsteins constant for the spontaneos emission, In my book they defined tau in the relation I...

Does anybody has any comment on this? What might cause it? B/c I don't want to explode. lol

I have an assignment for which I need the half-life of about 30 nuclei that decay through spontaneous fission. The total half-life is easy to find, but I need the half-life for spontaneous emission only. Does anyone know where I can find this? thanks, Levi

Hello! Just today, two of my video games have been absolutely wiped clean. All the data on both of them has been erased! :cry: I was wondering if there have been any recent solar flares or other electromagnetic disruptions that could cause this. I know it's a bit of a long shot, but I'm a...

The reaction A(g) --> B(g) is spontaneous under standard conditions. Which of the following statements must be true? I. B(g) --> A(g) is nonspontaneous under standard conditions. II. A(g) will be completely converted to B(g) if sufficient time is allowed. III. A(g) will be completely...

\mathcal{L} = \frac{1}{2}(\partial_{\mu}\underline{\phi}).(\partial^{\mu}\underline{\phi}) + \frac{1}{2}\mu^{2}\underline{\phi}.\underline{\phi} - \frac{\lambda}{4}(\underline{\phi}.\underline{\phi})^{2} + \bar{\psi}(i\gamma . \partial )\phi - g\bar{\psi}(\phi_{1}+i\gamma^{5}\phi_{2})\psi...

I often have this problem when reading physics books (the kind I can understand) where, because I'm only in High school math, the author explains only in analogies, and the analogies sometimes don't make logical sense. I'm reading Steven Weinberg's "Dreams of a Final Theory" and I got to the...

Hello. I've got a QFT final tomorrow, and one question is still bothering me. Consider two lagrangians. The first one is L = \frac{1}{2} D_{\mu} \vec{\phi}.D^{\mu} \vec{\phi} + \frac{m^{2}}{2} \vec{\phi}.\vec{\phi} - \frac{\lambda}{4} \left(\vec{\phi}.\vec{\phi}\right)^{2} The second...

I am having trouble understanding this.. If reactions are spontaneous when they create more entropy (disorder), why is it that most spontaneous reactions are exothermic? Such as an exothermic reaction like A + B ---> AB + Energy, AB then has lower energy than the reactants, which also means...

"SYDNEY (Reuters) - An Australian man built up a 40,000-volt charge of static electricity in his clothes as he walked, leaving a trail of scorched carpet and molten plastic and forcing firefighters to evacuate a building." http://news.yahoo.com/s/nm/australia_electricity_dc

Does anybody have an enough simple example and explanation of spontaneous breaking symmetry in quantum mechanics? When does the process of breaking take place? After or before some small perturbation appears?

any isolated macroscopic system, like a large group of atoms, always tends to reach a state that has the maxium entropy. if the electrons in this group of atoms are excited, they will give out their energy so that more degrees of freedom are activated, hence the entropy of the whole system...

Can someone please explain why an excited electron in an atom decays to the ground state, if energy eigenstates are stationary states.

Can anybody direct me to a discussion on the effects of a sudden reduction of the Earth's gravity - say by 50%? Purely speculative, of course. I'm assuming its orbit around the sun would be essentially unchanged, but that the moon would recede or maybe head off on its own merry way. Any other...

Which of these is spontaneous?? Which of the following are spontaneous at constant T and P ? (a) DH = -10 KJ DS = +5 J/K T = 298K (b) DH = +5 KJ DS = -5 J/K T = 10K (c) DH = -10 KJ DS = -40 J/K T = 300K (d) DH = -10 KJ DS = -40 J/K T =...

http://arxiv.org/pdf/gr-qc/0501014 A static 10 dimensional universe can arise spontaneously, by a quantum fluctuation?

Hey this is a weird subject but have any of you ever thought about what causes it, if it is indeed real? I have a theory but it may be totally wrong as I don't have a background in physics or chemistry. Well I read about solar neutrinos and how they pass through our bodies all the time. They...