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34 views

Infinitesimal transformation by Noether's charge [on hold]

Can anybody explain me the physics of the commutation relation : $ [Q,\phi_{i}] = it_{ij}\phi_{j}$ ; where, Q is Noether's charge and $\phi_{i} (i=1,2)$ are components of an isodoublet?
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0answers
36 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 ...
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1answer
36 views

One-point function and VEV 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 ...
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1answer
40 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?
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0answers
37 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 ...
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2answers
57 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 ...
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1answer
117 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} ...
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0answers
40 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 ...
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0answers
39 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
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0answers
23 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
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0answers
53 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 ...
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0answers
31 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 ...
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1answer
65 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 ...
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0answers
18 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
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0answers
37 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 ...
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0answers
19 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?
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0answers
39 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!
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0answers
27 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 ...
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1answer
61 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
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1answer
78 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
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0answers
77 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 ...
2
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0answers
74 views

Goldstone's theorem massless states

I'm currently trying to wrap my head around Goldstone's theorem proof as given by Itzykson & Zuber. The reasoning is pretty straightforward, but there's a result that's bothering me from a ...
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3answers
157 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 ...
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0answers
86 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 ...
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1answer
123 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 ...
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1answer
42 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 ...
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1answer
44 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 ...
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2answers
99 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
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1answer
58 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
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5answers
206 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 ...
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0answers
33 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 ...
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0answers
27 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 $$ ...
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1answer
73 views

Is sound a Nambu-Goldstone mode?

The usual sound exists in solids, liquids, and gases, as a long-wavelength excitation with linear dispersion. Can its presence be attributed to the spontaneous breaking of some symmetry? In other ...
2
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1answer
49 views

Can anyone explain to a novice physicist whether there is a gravitational-electromagnetic symmetry?

I am trying to understand how the four fundamental forces relate to one another and to a theory of everything. As I understand it the unified force that is thought to exist at very high energies gets ...
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1answer
144 views

Is Elitzur's theorem valid only in lattice field theory?

Elitzur's theorem, stating that spontaneous breakdown of a gauge symmetry is impossible, was originally proved for a lattice gauge theory. Is it valid in continuum field theory? Any ref?
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1answer
133 views

Is $SU(2)$ really broken by the Higgs VEV or just hidden?

It's generally stated in the textbooks that whent the Higgs field acquires a certain vev the corresponding symmetry is spontaneously broken. For example in A. Zee - QFT in a Nutshell: But none of ...
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1answer
60 views

Why should Ward identities only be used with the effective action (as opposed to the generating functional for connected diagrams)?

My question is about the derivation of Ward identities. I will sketch it here in the case of an O(N) symmetric model and point out what it bothering me when I am done. I am being very sloppy with the ...
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1answer
91 views

Where does in GUT symmetry breaking $U(1)$ come from?

In GUTs one starts with some larger group, like $SU(5)$, which is then broken into smaller groups, for example $$SU(5) ~\longrightarrow~ SU(3) \times SU(2) \times U(1)$$ This can be seen, for ...
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0answers
24 views

Electroweak symmetry breaking with additional gauge group(s)

Is it possible that rather than the electroweak splitting into SU(2)xU(1), that there could instead of another gauge group in the dark sector? Suppose SU(2)xU(1)xSU(N)_d. Is that ruled out by the full ...
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0answers
38 views

Charge renormalization point in massive abelian gauge theory

Let's assume massless QED. The Ward identities hold. Through this identity we determine the finite part of the counterterm when fix the value of electric charge to be the experimentally observed one: ...
2
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1answer
320 views

Why are we allowed to spontaneously break the Higgs field symmetry?

In the lepton Lagrangian there are no mass terms allowed for the gauge bosons, due to gauge symmetry. To fix the problem of existing gauge boson masses, we introduce another field (Higgs) and say that ...
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0answers
25 views

Do any, all, or no adjustments to standard model change the Weinberg angle or it’s relation to masses or coupling constants?

Do any, all, or no adjustments to standard model change the Weinberg angle or it’s relation to masses or coupling constants? If any, which (types of) ones? For the ones that do, what are the relations ...
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2answers
94 views

Why does the Higgs field have less energy when it's non-zero than when it's zero?

Why does the Higgs field have less energy when it's non-zero than when it's zero? There are references to this question on the site, but they are too heavy going for me for a while yet. Anybody want ...
3
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2answers
111 views

Functional integral in spontaneous symmetry breaking

So, functional integral is defined to be (with $\lvert\Omega\rangle$ is the vacuum state): $$\frac{\langle\Omega\rvert ... \lvert\Omega\rangle}{\langle\Omega\vert\Omega\rangle} = \int \mathcal{D} ...
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2answers
165 views

Spontaneous Symmetry Breaking - struggling with physics based understanding?

Although I am a mathematician by nature, I'm writing an essay in my third year of my undergraduate on Spontaneous Symmetry Breaking in Physics, and as such I've become a little confused by how the ...
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0answers
51 views

Interpretation of vector mesons in QCD

It is well-known that scalar mesons are interpreted as pseudogoldstone bosons which is connected with spontaneous broken $SU(3) \times SU(3)$ symmetry to $SU(3) \times SU(3) / SU(3)_{chiral}$. Is ...
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0answers
40 views

Weinberg's spontaneous broken symmetries

Steven Weinberg in his second volume of QFT's book (in section about spontaneously broken symmetries, in subsection about Goldstone bosons) writes following: if we have linear transformation of ...
3
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2answers
98 views

Simplest example of spontaneous breaking of time reversal symmetry

Consider a two-dimensional fluid flow, confined to a square, where the bottom is held at a higher temperature than the top. With appropriate choices of the parameters, this will form a single ...
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1answer
75 views

Why Levi-Civita term signal the breaking of parity and time reversal?

For example, referring to Zee's QFT book, in Chern-Simons matter theory, after writing a term $$\gamma {\varepsilon ^{\mu \nu \lambda }}{a_\mu }{\partial _\nu}{a_\lambda }$$ he said The ...
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0answers
57 views

Lorentz violation in String theory

First of all, why are there so many researches to find Lorentz violation? Are there some models of (super-)string theory that include Lorentz violation at some scale?