# Tagged Questions

We say that something is symmetric if there is some transformation we can perform on that object that leaves some property unchanged. The set of symmetry transformations of an object form a group, and the name of this group is used as the name of the symmetry of the object.

386 views

### Are black holes perfect spheres?

What I know about black holes (correct me if I'm wrong) is that they are the most compact objects in the universe that have been discovered. Due to all that gravity, wouldn't black holes be a perfect ...
54 views

### Two particles system

Source: this video For a system with two particles (09:30), why is its wave function a product of each particle's wave function? E.g. $$\psi(x_1,x_2)=\psi_a(x_1)\psi_b(x_2)$$ For indistinguishable ...
14 views

### Sublattice symmetry vs Particle hole symmetry

Sublattice symmetry and particle hole symmetry generally constrain a system's energy spectrum to be symmetric with respect to fermi level. My understanding is that they are both represented by an ...
52 views

167 views

### Para and ortho hydrogen angular momentum values

In Wikipedia, it is said that: Orthohydrogen, with symmetric nuclear spin functions, can only have rotational wavefunctions that are antisymmetric with respect to permutation of the two protons. ...
63 views

### Why is there a matter-dark matter asymmetry?

It is said generally that nature is symmetric. For example if light behaves as both a particle and a wave, then matter must also do so, which turns out to be true. But we find that the Universe ...
55 views

### Could dark matter possibly be anti-matter?

Considering the broken symmetry after the big bang - what I understand as there being a huge surplus of matter and a lesser presence of anti matter - is it possible that dark matter could be anti-...
151 views

### Derivations of Newton's laws?

I feel convinced that the mathematics behind newtons laws can be derived from Noether's symmetry theorems. The fact that displacement s can be described by a cartesian coordinate system with a ...
30 views

### Hexagonal shape of snow flakes [duplicate]

As we know snowflakes has hexagonal shape. My question is why is that? and Is there any mathematical model which can explain that particular geometric shape of the snowflakes?
659 views

### Vibrational anharmonic coupling and noise-induced spontaneous symmetry breaking in a hexagonal finite mechanical lattice

Happy holidays, everyone! The following is part question, part visual gallery, and part classical mechanics problem. Inspired by snow over the weekend I began simulating the vibrations of the ...
273 views

### Mechanics Landau Galilean Principle

I started reading Landau's Mechanics book and was having some trouble understanding the Galilean Relativity Principle. What does Landau mean by saying space to be homogenous and isotropic and time is ...
91 views

### The Mechanism Behind Massless Particles Acting As One Massive Particle

I am reading a historical account of the development of the Higgs Field theory by Sean Carroll. In it, he states that the 1963 paper by Anderson postulated that "the massless Nambu-Goldstone bosons ...
26 views

### Can an azimuthally symmetric perturbation lift the 2l+1 degeneracy of angular momentum eigenstates?

Assume the initial Hamiltonian of a spinless, non relativistic particle is $$H_0(r,\theta,\phi)=\frac{{\bf p}^2}{2m}+V_0(r)$$ Such that the eigenstates are angular momentum eigenstates $|n,l,m>$, ...
29 views

### Why is charge conjugation multiplicative?

I'm reading Mann's book on the standard model and particle physics and he doesn't explain why C symmetry is multiplicative other than saying it's discrete which isn't very convincing to me. In ...
51 views

### What does it mean to say “internal symmetry”?

What does it mean to say "internal symmetry"? Let me try to express the way I see it, so you can have it as a starting point. There are spacetime symmetries, which are global since any Lorentz ...
1k views

### Gauge redundancies and global symmetries [closed]

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 ...
100 views

### Is the Potential Energy just a bookkeeping device?

It is said that if the space is homogeneous then momentum is conserved. But I've been thinking in the following situation: Consider a parallel plates capacitor. In between the plates there is a ...
40 views

### Homogenity and Isotropicity of space

In school it is given that law of conservation of momentum is a result of homogeneity of space and law of conservation of angular momentum is a result of isotropicity of space but what is isotropicity ...
282 views

81 views

### Why is quark flavor just a SU(N) group?

In the standard model one has U(1) for electromagnetism, SU(2) for the weak sector and SU(3) for the color sector. One could say that in the quark part of the fermions, there are  \underbrace{6}_\...