Theory Definition and 1000 Threads

Hi PF, im finishing my bachelor soon and I would really like to do my thesis in De Broglie-Bohm theory. I know its a controversial topic but i refuse to accept the statistical crazyness of qm(i passed qm already). Im not a super good student so I´m asking you for some books on this theory, or...

Homework Statement I'm having issues understanding a mistake that I'm making, any assistance is appreciated! I know a counterexample but my attempt at proving the proposition is what's troubling me. Prove or disprove $$P(A \cup B) \subseteq P(A) \cup P(B) $$ Homework EquationsThe Attempt at...

Hello to everyone that's reading this. :) 1. Homework Statement (Theory of Computation) proof problem about proving that L = L(A) by proving that L ⊆ L(A) and that L(A) ⊆ L: https://www.docdroid.net/du7lLvh/theproblemanditssolution.pdf Homework Equations • Mutual simple induction • Formal...

Is there a fundamental equation in string theory and can it be derived from a variational principle?

I teach group theory for physicists, and I like to teach it following some papers. In general my students work with condensed matter, so I discuss group theory following these papers: [1] Group Theory and Normal Modes, American Journal of Physics 36, 529 (1968) [2] Nonsymmorphic Symmetries and...

This is one of the problems I'm currently working on but understanding how to deduce the Feynman rules for this case would give me a better idea on how to do it for more general cases besides ##\phi^4## theory (which is the example commonly covered in books like Peskin and Greiner). 1. Homework...

I am looking for good references / clarifications on the subject. First of all, my question is concerned only with mathematical formulation of something that sort of plays the role of the Feynman path integral of the "standard" QFT. It is not concerned with the physical or philosophical...

Hi, I’m interested in self studying so that I can learn / understand integrated information theory about counciousness. I was wondering if anyone could help me identify what courses (I’m looking at using MIT’s opencourseware to study although just types of math is all that is needed) I would...

I do have a fair amount of visual/geometric understanding of groups, but when I start solving problems I always wind up relying on my algebraic intuition, i.e. experience with forms of symbolic expression that arise from theorems, definitions, and brute symbolic manipulation. I even came up with...

Problem: Let $E$ have finite outer measure. Show that $E$ is measurable if and only if there is a $F_\sigma$ set $F \subset E$ with $m^*\left(F\right)=m^*\left(E\right)$. Proof: "$\leftarrow$" To Show: $E=K\cup N$ where $K$ is $F_\sigma$ and $m^*(N)=m(N)=0$. By assumption, $\exists F$, and...

I studied the work of a nano generator in quantu mechanics. The generator uses the principle of triboelectrics. How does this work in quantum field theory? I think that the electron (wave packet in the field) is in the atom in a small volume because the nucleus inhibits the propagation of the...

I have a Theory providing an alternative behavior of gravity and an explanation for the perception of dark matter. The math works at least in the large scale (not quantum). How do I publish this for the physics world to see? I want my Nobel Prize (joking). Legitimate answers would be highly...

hi Just a little question. How does one calculate the power of a QCL by theory? Is there any free software that allows one to calculate the power of a inputted laser medium for a qcl? Thanks. Adrian

Homework Statement Let ##U_1, U_2, U_3## be independent uniform on ##[0,1]##. a) Find the joint density function of ##U_{(1)}, U_{(2)}, U_{(3)}##. b) The locations of three gas stations are independently and randomly placed along a mile of highway. What is the probability that no two gas...

So, basically, multiverse make sense because we can't imagine our universe standing in nothing(or being everything that just expands itself). If we take this principle, we should have a multi-multiverse, a multi-multi-multiverse and so on. (When the chain ends?). Is it more evidence to support...

Hello Everyone, I am trying to write the intersection of a physical problem in the most compact way. I am not really familiar with Set Theory notation, but I think it has the answer. It is about the intersection of two circular areas: - Area 1: A - Area 2: B If I want to write this in Set...

where can I find the thoroughly discussed Hartree and Hartree-Fock method for many electrons system?

Homework Statement Prove the following for a given universe U A⊆B if and only if A∩(B compliment) = ∅ Homework EquationsThe Attempt at a Solution Assume A,B, (B compliment) are not ∅ if A∩(B compliment) = ∅, x∈A ∨ x∈ (B compliment), but not both If x∈A ∧ x∉(B compliment), then x∈B , because...

This isn't explained anywhere so it must be super basic and I'll probably kick myself for not getting it, but on the wiki page for time independent perturbation theory, section 3.1: https://en.wikipedia.org/wiki/Perturbation_theory_(quantum_mechanics) It talks about first order corrections and...

Was there any need or utility or aim, for which Cantor created his theory? Did Cantor's theory clear any of the problems which existed before? (Though my user name is Cantor, I don't know lot about him or his theory :biggrin:) Reddit...

- The wavelength of light doesn't change at all in the galaxies because the space of the galaxies doesn't expand. - The wavelength of light should be different when it passes through the galaxy or not. However, this is contradictory to the observed result. So, the big bang theory is wrong.

Hey, I am currently busy with studying solid state physics and looking at diffraction theory. Following link explains Frauenhofer diffraction pretty good: http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/mulslid.html#c3 Let's assume a N=6 multiple slits. Its diffraction pattern depends on slit...

Hello My friend claims that the theory of electron superposition has been overturned recently. That this was due to measurement errors, and that electrons fly like orbs and planets in orbits, but I can not find any sources. I am asking for an answer, thank you very much. (I'm sorry, I have no...

Homework Statement Show that, in the Debye theory, the number of excited vibrational modes in the frequency range ##\nu## to ##\nu+d\nu##, at temperature T, is proportional to x2e-x, where ##x=h\nu/kT##. The maximum in this function occurs at a frequency ##\nu'=2kT/h##; hence ##\nu'→0## as...

Homework Statement Hi all, I have some difficulty understanding the following problem, help is greatly appreciated! Let ##U_1, U_2, U_3## be independent random variables uniform on ##[0,1]##. Find the probability that the roots of the quadratic ##U_1 x^2 + U_2 x + U3## are real. Homework...

Alright guys...for the past month and a half my chemistry class consisted on lectures on chemical bonding. From the days of Kossel and Lewis To modern concepts of VSEPR,Hybridisation and Molecular orbital theory. According to Wikipedia they say the two basic models based on quantum mechanics...

Homework Statement Let ##S = \{(x_1, \dots, x_p) \mid x_i \in G, x_1 x_2 \cdots x_p = e\}##. Let ##C_p## denote cyclic subgroup of ##S_p## of order ##p## generated by the ##p##-cycle, ##\sigma = (1 \, 2 \, \cdots \, p)##. Show that the following rule gives an action of ##C_p## on ##S## $$...

This is a topic I've mentioned a few times before. Essentially the structure of matter in quantum gauge field theories is unclear to me. I have no clear question here, just some initial discussion points. So at the first level, it seems a particle based view of quantum field theory is difficult...

Homework Statement For this question , I tried to use L' = L -2e and B '= B , i ended up getting different final answer when i use L ' = L , B'= B -2e In the notes , we can see that if the eccentricity were in the direction of length of the foundation , L '= L-2e , and B'= B ... But , in this...

All the literature on the quantum eraser that I've seen is grounded in the Copenhagen interpretation of quantum mechanics. It's very easy to understand the experiment in those terms. Do you know how quantum eraser experiments are interpreted by the de Broglie–Bohm theory? What is erased in this...

Bohmian mechanics requires a preferred reference frame. But String theory doesn't have any preferred frames, so isn't BM incompatible with ST?? Maybe it would be compatible with other theories of quantum gravity that permit a preferred frame (LQG, CDT)...

Homework Statement Decide all abelian groups of order 675. Find an element of order 45 in each one of the groups, if it exists. Homework Equations /propositions/definitions[/B] Fundamental Theorem of Finite Abelian Groups Lagrange's Theorem and its corollaries (not sure if helpful for this...

Hi , I need to enrich my knowledge in quantum field theory, please refer me to reference books in this branch. Thank's.

Hi guys, something has been bugging me for a while now and I thought I’d just ask it here in the hope someone can explain it to me. Ever since Elon Musk brought it up, I’ve been thinking about the simulation theory (I know it’s not his original idea, it’s just the event that brought it to my...

Earlier this morning I came across this article -- https://phys.org/news/2018-09-errors-quantum-world.html -- which is about an open for all article in Nature Communications -- https://www.nature.com/articles/s41467-018-05739-8 I've yet to fully work through the paper, but if this thread is...

Take the first family of fundamental fermions, u, d, e-, and ν. The u and d are more massive than the e- and the e- is more massive than the ν. The u and d interact via 4 forces, the e- interacts via 3 forces, and the ν interacts via 2 forces. The fermions that interact via the most forces are...

Homework Statement [/B] Hi all, I have an issue understanding the concepts pertaining to the following problem, assistance is greatly appreciated. I understand the "flow" of the problem; first find the probability of obtaining balls of the same colour, then use the geometric distribution...

I would like to learn (self-study) the theory behind the n-dimensional Riemann integral (multiple Riemann integrals, not Lebesgue integral). I am from Croatia and found lecture notes which Croatian students use but they are not suitable for self-study. The notes seem to be based on the book: J...

Do the the different calabi-yau space solutions of strings theory exist is isolated space-times or are they a part of a continuous whole with space folding and unfolding as you move though space?

I have been reading some papers from G.F. Chew and S. C. Frautschi and they do not even bother to introduce the concept of "Field" when they describe hadron interactions. My impression is that they do not need to because interactions seem to be described by single Regge-trajectories. However...

Homework Statement Discrete random variables ##X,Y,Z## are mutually independent if for all ##x_i, y_j, z_k##, $$P(X=x_i \wedge Y=y_j \wedge Z=z_k ) = P(X=x_i)P(Y=y_j)P(Z=z_k )$$ I am trying to show (or trying to understand how someone has shown) that ##X,Y## are also independent as a result...

I know it's hard to predict but what are the probable outcomes? When I hear about the theory of everything in different situations it always makes me feel that we really want to believe that it will be a final fundamental theory. How could the theoretical work look like after its success...

I am reading Steve Awodey's book: Category Theory (Second Edition) and am focused on Section 1.5 Isomorphisms ... I need some further help in order to fully understand some aspects of Definition 1.4, Page 12 ... ... The start of Section 1.5, including Definition 1.4 ... reads as...

I am reading Steve Awodey's book: Category Theory (Second Edition) and am focused on Section 1.5 Isomorphisms ... I need some further help in order to fully understand some further aspects of Definition 1.3, Page 12, including some remarks Awodey makes after the text of the definition ... ...

Homework Statement Hi all, could someone give my working a quick skim to see if it checks out? Many thanks in advance. Suppose that 5 cards are dealt from a 52-card deck. What is the probability of drawing at least two kings given that there is at least one king?Homework Equations The Attempt...

Homework Statement Problem: We want a closed loop control loop for the given process (see bode plot), the control loop requirements are: Steady state error needs to be zero. The gain margin needs to be infinite. The phase margin needs to be 40 degrees. Questions: Which controller will be...

I am reading Tom Leinster's book: "Basic Category Theory" and am focused on Chapter 1: Introduction where Leinster explains the basic idea of universal properties ... I need help in order to fully understand the proof of Lemma 0.7 ... Lemma 0.7 and its proof read as follows:In the above proof...

Hello, i would like to ask You a question about difference in results between Euler-Bernoulli method of analysis of stress in short slender beam and 3D FEA method mentioned in ansys aim tutorial here: https://confluence.cornell.edu/pages/viewpage.action?pageId=33636829 The problem looks like...

This is related to string theory

Suppose that ##n,j \in \mathbb{N}##, ##j \in [0, n-1]##, and ##n~|~2j##. Why is it the case that ##j = 0## or ##2j = n##? This is used in a proof of something else, but I am getting tripped up on this part. I know it has to do with the fact that ##j \in [0, n-1]##. Is it because ##n## can't ever...