The symmetry tag has no wiki summary.
11
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6answers
1k views
What is the symmetry which is responsible for conservation of mass?
According to Noether's theorem, all conservation laws originate from invariance of a system to shifts in a certain space. For example conservation of energy stems from invariance to time translation.
...
1
vote
1answer
195 views
Conserved quantum observables from symmetries *with density matrix*
I’ve read Ballentine where he derives the conserved observable operators (momentum, energy, ...) from symmetries of space-time.
Can I read up such a derivation in more detail somewhere else or even ...
1
vote
1answer
367 views
Weinberg's way of deriving Lie algebra related to a Lie group
I was reading the second chapter of the first volume of Weinberg's books on QFT. I am quite confused by the way he derives the Lie algebra of a connected Lie group.
He starts with a connected Lie ...
10
votes
4answers
725 views
QM and Renormalization (layman)
I was reading Michio Kaku's Beyond Einstein. In it, I think, he explains that when physicsts treat a particle as a geometric point they end up with infinity when calculating the strength of the ...
2
votes
2answers
210 views
Correlation Functions, Symmetries and Measurements
Is there a book that goes deep into correlation functions? What I'm interested in a book/article that explains in the detail the relation of the correlation functions with symmetries and how one can ...
5
votes
2answers
364 views
What's the importance of Noether's theorem in Physics
The Noether's theorem that I want to mention is the following: Noether's theorem.
I know the importance of Noether's contribution to modern algebra. Can anyone write about Noether's theorem in ...
6
votes
2answers
376 views
Why are conformal transformations so prevalent in physics?
What is it about conformal transformations that make them so widely applicable in physics?
These preserve angles, in other words directions (locally), and I can understand that might be useful. Also, ...
2
votes
2answers
157 views
What are the limitations of the FLRW metric?
I was wondering, given how in any other area of life making an explosion spherically symmetric is more or less impossible is there any reason to expect that the universe is? I appreciate that the FLRW ...
2
votes
1answer
129 views
Similar masses and lifetimes of the $\Delta$ baryons
Why do the four spin 3/2 $\Delta$ baryons have nearly identical masses and lifetimes despite their very different $u$ and $d$ quark compositions?
3
votes
0answers
115 views
Symmetries of separable potential
For separable potential, say $x^4+y^4$, its symmetry are degenerate.
Is that a generic case to every separable potential? I will explain my question:
The potential $x^4+y^4$ has $A_1, B_1, A_2, B_2, ...
2
votes
1answer
173 views
How to perform a scale (invariance) transformation?
According to this wikipedia article in the $\phi^4$ section, the equation
$$\frac{1}{c^2}\frac{∂^2}{∂t^2}\phi(x,t)-\sum_i\frac{∂^2}{∂x_i^2}\phi(x,t)+g\ \phi(x,t)^3=0,$$
in 4 dimensions is invariant ...
4
votes
2answers
252 views
Is there a 1-1 correspondence between symmetry and group theory?
The professor in my class of mathematical physics introduces the definition of groups and said that group theory is the mathematics of symmetry.
He gave also some examples of groups such as the set ...
7
votes
2answers
322 views
Groups acting on physics - a clarification on electrons and spin
My first question is fairly basic, but I would like to clarify my understanding. The second question is to turn this into something worth answering.
Consider a relativistic electron, described by a ...
2
votes
2answers
204 views
Which symmetry is associated with conservation of flux?
Which symmetry is associated with conservation of flux (e.g., in electromagnetism)?
For example, when working with Gauss's law in electromagnetism, net flux through an arbitrary volume element ...
4
votes
0answers
313 views
Gauge redundancies and global symmetries
It is often said that local (gauge) transformation is only redundancy of description of spin one massless particles, to make the number degrees of freedom from three to two. It is often said that ...
1
vote
1answer
257 views
Understanding P-, CP-, CPT-violation etc. in field theory and in relation to the principle of relativity
I can never get my head around the violations of $P-$, $CP-$, $CPT-$ violations and their friends. Since the single term "symmetry" is so overused in physics and one has for example to watch out and ...
3
votes
2answers
551 views
The Energy-Momentum Tensor and the Ward Identity
I have a question regarding a homework problem for my quantum field theory assignment.
For the purposes of the question, we can just assume the Lagrangian is that of a real scalar field:
...
9
votes
2answers
375 views
The Ozma Problem
The "Ozma problem" was coined by Martin Gardner in his book "The Ambidextrous Universe", based on Project Ozma. Gardner claims that the problem of explaining the humans left-right convention would ...
7
votes
2answers
179 views
Particles mass determined by SO(D-2) vs SO(D-1)
I've recently come across this statement that massless particles arise from $SO(D-2)$ symetry and massive particles from $SO(D-1)$.
I would have guessed that it would be the exact opposite way, but ...
1
vote
1answer
965 views
Symmetric potential and the commutator of parity and hamiltonian
In one dimension -
How can one prove that the Hammiltonian and the parity operator commute in the case where the potential is symmetric (an even function)?
i.e. that [H, P] = 0 for V(x)=V(-x)
8
votes
2answers
876 views
Poincare group vs Galilean group
One can define the Poincare group as the group of isometries of the Minkowski space. Is its Lie algebra given either by the equations 2.4.12 to 2.4.14 (..as also given in this page - ...
2
votes
3answers
265 views
About symmetry, and about electron density in crystals in particular
The book Introduction to Solid State Physics by Kittel says:
"We have seen that a crystal is invariant under any translation of the form T [...]. Any local physical property of the crystal, such as ...
1
vote
3answers
379 views
Noether's theorem and “translations” of the Hamiltonian function
In a nutshell, Noether's theorem states that for every continuous symmetry a corresponding conserved quantity exists.
Now, the Hamiltonian equations of motion (let's talk about a classical system ...
5
votes
2answers
1k views
Relation between total orbital angular momentum and symmetry of the wavefunction
My question essentially revolves around multi-electron atoms and spectroscopic terms. I understand the idea that the total wavefunction for Fermions should be antisymmetric. Consider as an example, ...
11
votes
4answers
939 views
If all conserved quantities of a system are known, can they be explained by symmetries?
If a system has $N$ degrees of freedom (DOF) and therefore $N$ independent1 conserved quantities integrals of motion, can continuous symmetries with a total of $N$ parameters be found that deliver ...
2
votes
1answer
363 views
SU(N) symmetry and its representations
If a Lagrangian containing an N-multiplet of fields is invariant under global $\mathbf{SU}(N)$ transformations, does that necessarily imply it is invariant under $\mathbf{SU}(N-1)$, ...
5
votes
2answers
644 views
What does “soft” in “soft symmetry breaking” mean?
For example it is stated that if supersymmetry breaking is soft then stability of gauge hierarchy can be still maintained.
7
votes
3answers
405 views
Noether theorem with semigroup of symmetry instead of group
Suppose You have semigroup instead of typical group construction in Noether theorem. Is this interesting? In fact there is no time-reversal symmetry in the nature, right? At least not in the same ...
5
votes
2answers
501 views
Expansion in spherical harmonics in cubic symmetry
suppose I have an electrostatic potential which I expand in spherical harmonics via
$$\sum_{l,m} A^l_m r^n P_l^{|m|}(\cos \theta) e^{im\varphi}$$
and I know that the field has cubic symmetry. Is ...
4
votes
2answers
197 views
How do you derive Noether's theorem when the action combines chiral, antichiral, and full superspace?
How do you derive Noether's theorem when the action combines chiral, antichiral, and full superspace?
3
votes
1answer
687 views
Why must the deuteron wavefunction be antisymmetric?
Wikipedia article on deuterium says this:
The deuteron wavefunction must be
antisymmetric if the isospin
representation is used (since a proton
and a neutron are not identical
particles, ...
3
votes
2answers
317 views
Symmetry breaking
What is a good place to learn the details of symmetry breaking? What I am looking for is a more serious exposition than the wiki-article, which explains the details, especially the mathematical part, ...
1
vote
4answers
383 views
Is “real” antimatter (odd under C, P, T) unphysical?
A positron is odd under charge conjugation and parity reversal but nevertheless even with respect to time reversal. Is a theoretical positron which would be odd under all three symmetries (C, P, T) ...
6
votes
3answers
383 views
What sort of experiment would directly test time reversal invariance?
I guess the title says it all: how could/would you experimentally test whether our universe is truly time reversal invariant, without relying on the CPT theorem? What experiments have been proposed to ...
