In explicit symmetry breaking, the equations of motion of a physical system are variant under the broken symmetry; by contrast, for spontaneous symmetry breaking (SSB), these equations are invariant, but the entire system is not because its vacuum (background) is non-invariant. Further use for the ...

learn more… | top users | synonyms

0
votes
0answers
29 views

What is conformal symmetry physically?

I'm reading a paper by t'Hooft http://arxiv.org/abs/1410.6675. There is an argument in the paper that I could not understand: "Now that system, described by Maxwell’s equations, does have conformal ...
2
votes
2answers
44 views

Chiral symmetry breaking and confusion with terminology

I am confused about Chiral symmetry breaking and the terminology we use. First of all, I think the symmetry is started with taking quark masses zero and writing the Lagrangian as; $$ ...
3
votes
0answers
29 views

Topological terms VEVs and ghosts

Suppose we have the Standard model, and we want to calculate with VEVs of topological susceptibilities of $SU_{L}(2), U_{Y}(1)$ and $SU_{c}(3)$ fields, which have the form $$ \tag 1 \kappa \equiv ...
8
votes
2answers
159 views

Quantum Anomalies and Quantum Symmetries

In Quantum Field Theories (QFT) there is a well known phenomenon of anomalies, where a classical symmetry is broken in the quantum theory due to a so called anomaly. This symmetry breaking can be ...
2
votes
0answers
28 views

The nature of axion-like particle

Suppose that we have axion-like particle $\varphi$ theory, $$ \tag 1 S_{a} =\int d^{4}x\left(\frac{1}{2}(\partial_{\mu}\varphi )^{2} - \frac{m^{2}}{2}\varphi^{2} - \frac{\varphi}{f_{\varphi}}F_{\mu ...
3
votes
1answer
63 views

Why do the conserved charges in the case of SSB of a global symmetry not exist?

Reading "From Linear SUSY to Constrained Superfields" by Komargodski and Seiberg, I got a bit confused regarding the existence of the conserved charges in a theory with spontaneous symmetry breaking ...
0
votes
0answers
28 views

Feynman rules complex field in polar form

I am trying to derive the Feynman rules for this field: $$L=-\partial \phi^*\partial \phi - \frac{\lambda}4 (|\phi|^2-v^2)^2 $$ With this coordinates $\phi = \frac 1 {\sqrt2}\rho \exp(i \theta)$, ...
2
votes
1answer
66 views

Chiral current VEV below the QCD scale

Let's have pure QCD. I know that after spontaneous symmetry breaking quark bilinear form are replaced by their averaged values: $$ \bar{q}_{i}q_{j} \to \langle \bar{q}_{i}q_{j}\rangle \approx ...
2
votes
0answers
38 views

Difference between a Hamiltonian and its mean-field form?

In most solid state physics text books, BCS theory is introduced in the following way: The authors introduce a mean-field parameter (based on the superconduncting pair) and upon that, they reduce the ...
3
votes
1answer
46 views

Broken symmetries realized nonlinearly

I'm trying to understand some concepts of spontaneous symmetry breaking, I'll write first the statement that I can't understand and later my questions. STATEMENT Consider a group $G$ and a subgroup ...
3
votes
1answer
103 views

Doubts about spontaneous symmetry breaking

I have been exposed to the usual treatment about spontaneous symmetry breaking in the standard model but it shames me to admit that there are some loose ends I still have to tie up. For simplicity, ...
1
vote
1answer
113 views

Is the Higgs mechanism a gauge transformation or not? ( $U(1)$ context )

I'm trying to understand the way that the Higgs Mechanism is applied in the context of a $U(1)$ symmetry breaking scenario, meaning that I have a Higgs complex field ...
4
votes
1answer
64 views
+50

Soft SUSY breaking fermion mass terms in MSSM for matter fields

In the Minimal Supersymmetric Standard Model, the chiral fermion fields (the Higgsinos) don't have any soft SUSY breaking mass terms and soft SUSY breaking trilinear interactions while their scalar ...
0
votes
0answers
52 views

Magnetism in Topological Insulator?

I have read many papers with the statement that on the introduction of the magnetic impurity, the gap at the Dirac point opens in the surface states. I am little confused about it. If the gap is ...
3
votes
1answer
75 views

Spontaneous symmetry breaking of anomalous global abelian symmetries and $U(1)$ of QCD

Let me restate the $U(1)$ problem of QCD: Let us forget about the $s$ quark, and consider the $u$ and $d$ massless. This is a good approximation since $m_{u,d} \ll \Lambda_{QCD}$. Then ...
1
vote
0answers
76 views

What happens to Goldstone bosons in the Higgs potential after symmetry breaking?

When the gauge symmetry of our Lagrangian breaks spontaneously through the Higgs mechanism, we usually find that $n$ Higgs degrees of freedom become massless through the vacuum expecation value (vev), ...
0
votes
0answers
77 views

Higgs mechanism in 1+1 spacetime dimensions

I know there are problems with Goldstone's theorem, as stated by Coleman in http://projecteuclid.org/download/pdf_1/euclid.cmp/1103859034. What about Higgs mechanism? Can I possibly think of a ...
0
votes
0answers
22 views

How to compute remnant discrete charges?

When a $U(1)$ gauge symmetry is broken by Higgs field with $U(1)$ charge $g$, we have a remnant $\mathbb{Z}_q$ symmetry. How can I compute the corresponding charges under this remnant group for ...
1
vote
1answer
64 views

Center group and Symmetry breaking

First, I will state the definition of center, $i.e$, the center of group $C_G$ is defined a sthe part of $G$ which commutes with all generators. I want to know the procedure of breaking gauge ...
4
votes
1answer
65 views

How do symmetries break in cosmology?

The way I understand spontaneous symmetry breaking in thermodynamic systems is that the symmetry is actually explicitly broken by an infinitesimally small field. The system chooses one of the ...
0
votes
0answers
45 views

How can the VEV of a field be a function of spacetime?

Often in the discussion of effective action and effective potential (say, in the context of $\phi^4-$theory )the one-point function in presence of source is defined as \begin{equation} \frac{\delta ...
3
votes
1answer
77 views

One-point function and vacuum expectation value in $\phi^4$-theory

Why is it that the one-point function in the $\phi^4-$theory, for example calculated from the generating functional, always gives zero value in absence of external source i.e., $J=0$? If there is ...
1
vote
1answer
46 views

Is it possible to have spontaneous symmetry breaking without scalars?

I have never seen spontaneous symmetry breaking with a fermion filed, or a gauge field. Always scalars. So is it possible to have spontaneous symmetry breaking without scalars, and why?
1
vote
0answers
49 views

Given a VEV how can I compute which generators remain unbroken using tensor methods?

This is a follow up to this question. A generator $T_a$ of a given gauge group $G$ remains unbroken after some Higgs field $\Phi$ gets a vev if $$ T_a \langle\Phi\rangle =0 $$ I'm trying to ...
3
votes
2answers
72 views

Determination of the ground state of a field theory

Consider the Spontaneous symmetry breaking in the theory $$\mathcal{L}=\frac{1}{2}\partial_\mu\phi\partial^\mu\phi-\frac{\mu^2}{2}\phi^2+\frac{\lambda}{4!}\phi^4.$$ By the ground state of a ...
5
votes
1answer
145 views

Georgi-Glashow model and the VEV of the scalar field

Consider the Georgi-Glashow model, an $SU(2)$ gauge theory with a real scalar in the adjoint (thus a 3-vector in the colour space) $\phi$. The Lagrangian is $$ L = -\frac{1}{4g^2} F_{\mu \nu}^{\, a} ...
1
vote
0answers
54 views

Explicit Matrix Representation for 54 Higgs rerpesentation for $SO(10)\rightarrow$ Pati-Salam Breaking

Which Higgs field or linear combination of Higgs fields gets a vev if we want to break $$ SO(10) \rightarrow SU(4) \times SU(2) \times SU(2) ? $$ Formulated a bit differently, I'm looking for an ...
2
votes
0answers
49 views

Physical proceses before the breaking of $SU(2)_L\times U(1)_Y$ symmetry

The energy scale which the electromagnetic and the weak interaction were unified, there were 4 massless gauge bosons: 3 corresponding to the unbroken generators of $SU(2)_L$, say $W_{\mu}^{1,2,3}$ ...
2
votes
0answers
27 views

How to find the remaining subgroup after some linear combination of Higgs fields gets a VEV?

This is a follow-up question to this question. How can I compute which generators remain unbroken when a linear combination of Higgs fields $a \Phi_1+ b\Phi_2$ get a vev? If I compute the unbroken ...
2
votes
0answers
68 views

Books on superconductivity and its relation to spontaneous symmetry breaking

I wish to understand more about the relationship between superconductivity and spontaneous symmetry breaking. I would also appreciate sources for learning about symmetry breaking and particles in more ...
1
vote
0answers
38 views

Excitation spectrum of heisenberg model

I understand that ferromagnetic Heisenberg model (lattice of spin variables that can point in any direction) spectrum can be deduced by a $\lambda\phi^4$ theory with $\phi$ being complex. This model ...
2
votes
1answer
96 views

How are scale of renormalization and scale of symmetry breaking related?

If symmetry breaking, e.g. with a potential $V=-\mu^2\phi^2 + \lambda \phi^4 $ occurs at a certain energy scale, and I now evolve to another scale via the Callan-Symanzik equations, does that change ...
0
votes
0answers
21 views

Question on distinct phases through spontaneous symmetry breaking.

If I have a many-body Hamiltonian that is invariant under the representation of a certain group $G$ i.e [H,U(g)] = 0, how many phases does can exist through spontaneous symmetry breaking (SSB) of this ...
3
votes
0answers
43 views

Symmetry breaking to a special subalgebra?

This is a follow-up to my question here. For regular subalgebras of some group's Lie algebra the root system of the subalgebra is a subset of the root system of the original's group algebra. In ...
0
votes
0answers
23 views

Can a macroscopic passive system break the time-reversal symmetry spontaneously?

I know there are many systems can break T-symmetry if the internal source ALREADY chooses a direction of T. Without any driving source inside the system, can T-symmetry be broken spontaneously?
0
votes
0answers
40 views

Resource for (String) Symmetry Breaking in Terms of Roots and Weights?

I'm currently searching, for quite a while now, for a paper/book that discusses symmetry breaking in terms of roots and weights. Any suggestions would be much appreciated!
0
votes
0answers
40 views

Break time-reversal symmetry in photonic system without using bias magnetic field

In photonic system, e.g, photonic crystals, people usually use ferromagnetic material or so called Tellegen medium which acts as effective field bias to break the time-reversal symmetry. I just want ...
1
vote
1answer
88 views

Why didn't we have inflation when the theory of everything and GUTS broke symmetry?

I asked this in astronomy and they suggested I ask it here. Inflation seems to have occurred when the symmetry breaking of the electroweak occurred. But do we know of any reason why we did not have ...
2
votes
1answer
97 views

How to find the remaining subgroup after some Higgs field gets a VEV?

Say we have a group $G$ and a set of Higgs fields in a representation $R$ of $G$. One of the Higgs fields in $R$ gets a VEV, how can I determine the remaining subgroup after this symmetry breaking? ...
2
votes
0answers
85 views

Axion strings and spontaneously broken symmetry

I have two question about axion strings: Why their appearance is connected with spontaneously broken symmetry? How to demonstrate that? Why they are stable topological configurations (look to the ...
8
votes
4answers
386 views

What role does “spontaneously symmetry breaking” played in the “Higgs Mechanism”?

In talking about Higgs mechanism, the first part is always some introduction to the concept of spontaneously symmetry breaking (SSB), some people saying that Higgs mechanism is the results of SSB of ...
4
votes
0answers
108 views

Why does Wikipedia equate hidden symmetry with broken symmetry for the standard model?

I have recently started studying the basic ideas of symmetry and group representation in order to understand the basic principles behind the standard model. I do follow the difference between a global ...
0
votes
2answers
167 views

Is my understanding of Gauge Symmetries correct?

I'm currently working on a project about Symmetry Breaking for my physics bachelor. Right now I'm trying to understand Gauge Symmetries (although I guess it's not much of a symmetry). And I've been ...
1
vote
1answer
43 views

Transformations of electroweak gauge field $W_\mu$ under $U(1)_{e.m.}$

As the vector boson field $W_\mu$ is, together with $Z^0$, the gauge field for the Standard electroweak model, I know it transforms as a connection under the $SU(2)\times U(1)_Y$ group. But, when this ...
1
vote
1answer
54 views

Why we do we consider explicit SUSY breaking in the MSSM and not an spontaneous breaking of SUSY?

Reading about the minimal supersymmetric standard model (MSSM) I have found that an explicit breaking of supersymmetry is considered, given by the term $$\cal{L}_{soft}$$ where soft supersymmetry ...
0
votes
2answers
109 views

Solutions of symmetric equations are not invariant - is symmetry spontaneously broken?

I have a system of equations: \begin{cases} f\left(x_{1}\right)+f\left(x_{2}\right)+P=0\\ \\ g\left(x_{1}\right)+g\left(x_{2}\right)=0 \end{cases} where $f$ and $g$ are some functions, $P$ is a ...
2
votes
1answer
72 views

Poincare non-invariance in real world and field theory

This may be a very blunt question but I wonder why we always use Poincare invariant Lagrangians in field theory. After all, the entire world around us is by no means homogeneous, isotropic and so on. ...
2
votes
5answers
270 views

Which way will the pencil fall?

Let's say you had a perfect pencil, with a point which was just that one point (see this question). The pencil's mass was perfectly distributed, and there are no flaws in the craftsmanship. Let's say ...
0
votes
0answers
45 views

What are the limitations of simulating grand unification theories of elementary particles in condensed matter settings?

What are the limitations of simulating grand unification theories of elementary particles in condensed matter settings? I know that condensed matter systems can be constructed to be described by any ...
0
votes
0answers
37 views

How can we determine the Hypercharges in a GUT like SO(10)?

I understand how the assignment works for a symmetry breaking like $$SO(10) \rightarrow SU(3)_C \times SU(2)_L \times SU(2)_R \times U(1)_X$$ The Hypercharge can then easily computed by $$ ...