Questions tagged [higgs]

This higgs field breaks electroweak symmetry and provides mass to particles though a process called the higgs mechanism. The excitation of the higgs field is called a higgs boson.

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806 views

Penrose's Zig-Zag Model and Conservation of Momentum

I was reading through Penrose's Road to Reality when I saw his interesting description of the Dirac electron (Chapter 25, Section 2). He points out that in the two-spinor formalism, Dirac's one ...
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1k views

Coulomb Branch vs. Higgs Branch (and the connection with D-branes, AdS/CFT)

I am confused about the difference between the Coulomb and Higgs branches of the moduli space of supersymmetric gauge theories. It's easy to find a definition for $D=4$, $\mathcal{N}=2$ supersymmetric ...
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115 views

axial and vector resonances in composite higgs models

Is there a reason to believe that the axial resonances be heavier than the vector resonances in the composite higgs models? For instance, in http://arxiv.org/abs/0808.2071, to have zero tree level ...
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144 views

Finite corrections to the Higgs mass in SUSY

I am worried here about specific supersymmetric scenarios in which an energy scale above the TeV is introduces. An example would be the Seesaw extension of the Minimal Supersymmetric Standard Model. ...
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463 views

Could sphaleron-induced proton decay also cause vacuum decay?

I will say right away that I don't mean standard-model sphalerons, I mean the sphalerons of some extension of the standard model. The reason to even think about this is last year's paper by Frampton ...
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226 views

Is the vacuum degenerate in the Abelian Higgs model?

Consider the theory with Lagrangian $$ \mathcal{L} = -\frac{1}{4}F_{\mu \nu} F^{\mu \nu} + (D_\mu \phi)^* (D^\mu \phi) - U(\phi) \,, $$ where $U(\phi)$ breaks the $U(1)$ symmetry of the system. If we ...
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328 views

A question about spontaneous symmetry breaking at macroscopic limit

The question relates to this post. Spontaneous symmetry breaking is somehow a volume effect, that in-principle only happens at infinity large system. Weinberg in the second volume of his QFT used a ...
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448 views

Is the Higgs bare mass larger than the physical mass?

The Higgs boson propagator can be written $$\frac{1}{p^2-m^2+\Sigma(p^2)}$$. If we take $p^2=m_P^2$ the physical mass, we get $m_P^2=m^2-\Sigma(m_P^2)$. Now, if $\Sigma\sim \Lambda^2$, we get $m^2\sim\...
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43 views

(Why) Can we simply assume a given alignment of VEVs?

In GUT theories, one often assumes that Higgs fields take VEVs in given representations, of a given magnitude at a given scale. While I am well aware that this is one of the weak spots in such ...
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180 views

Could one theoretically build the Higgs equivalent of a Faraday cage?

My understanding is, within quantum mechanics, in a pure vacuum, all known fields have a lowest energy state of zero. The Higgs field is the only exception -- it's lowest energy state is not zero. ...
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If the gauge symmetry is not broken by spontaneous symmetry breaking, what symmetry is broken?

In this post, the answer by buzhidao showed that the $U(1)$ gauge symmetry is not broken by spontanous symmetry broken and Higgs mechanism. What role does "spontaneously symmetry breaking" ...
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230 views

Beta function for non-Abelian gauge theory with both fermionic and bosonic matter fields

Consider a non-Abelian gauge theory with both fermionic $\psi$ and bosonic $\phi$ matter fields in 4D, which may be called a QCD-Higgs model, $$L=-\frac{1}{4 g^2}F_{\mu\nu}F^{\mu\nu}+\bar{\psi}i\gamma^...
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292 views

What is the relation between Bose Einstein Condensate of Higgs and the Higgs field?

I have been wondering the relation between Higgs BEC and Higgs field. During reheating of the universe, people always claim the energy density of inflaton drops down like massive particles without ...
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175 views

Indefinite Number of Particles in BCS Superconductor and the Higgs-Anderson Mechanism

In general, the BCS ground state wave function can be written as $$|\psi_G\rangle=\prod_k (|u_k|+e^{i\theta}|v_k|c_{k\uparrow}^\dagger c_{-k\downarrow}^\dagger)|\phi_0\rangle $$ According to ...
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Electromagnetic sector in a spontaneously broken theory

Consider a Higgs-Yang-Mills system, where the Yang-Mills field is a connection 1-form on the $G$-principal bundle $P\to M$ and the Higgs field is a section of the associated vector bundle $E=P{{\times ...
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152 views

Running coupling, effective potential and the stability of vacuum

Consider the potential $$V(\phi)=\frac{1}{2}\mu^2\phi^2+\lambda\phi^4$$ where $\phi=\phi(t,\textbf{x})$ is a real scalar field. Let, $\mu^2<0$ and $\lambda>0$ then the potential is bounded from ...
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96 views

Why do we need any model beyond SM to fine-tune the Higgs mass?

ATLAS and CMS combined their results recently and it shows that higgs mass is ~125 GeV. Theoretical physicists try to figure out the "low mass" of the Higgs which causes hierarchy problem at high ...
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172 views

Could we Bose-condense Higgs bosons?

Apart from the obvious problem that we'd have to create enough of them and somehow not let them decay, is there anything that would prevent a Higgs boson condensate?
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333 views

Fields with SO(3) diagonal subgroup symmetry

I read about a Higgs field $\vec{\phi}=\frac{1}{2}a\hat{r}\cdot \vec{\sigma}$ (in the context of 't Hooft-Polyakov monopole) with SO(3) diagonal subgroup symmetry consisting of simultaneous and equal ...
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223 views

Higgs stability in Standard Model

I am a little unclear on what ramifications a negative quartic at high energies has on our world at low energies. (1) First of all, is it that there is a second, isolated minimum that appears at ...
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114 views

QFT Superposition and the Higgs Ground State

In a quantum theory with zero spatial dimensions with Hamiltonian given by: $$H = \pi^\dagger \pi + \mu^2 \phi^\dagger \phi - \lambda (\phi^\dagger \phi)^2,$$ where the non hermitian field, $\phi$, is ...
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90 views

Massless excitations without SSB

Is there a possible situation where there are massless excitations in spectrum of states in a theory with phase transition but without spontaneous symmetry breaking? The motivation for this question ...
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140 views

What are the Higgs masses for $SU(2) \times U(1)$ goes to $U(1)$ symmetry breaking with a complex triplet?

Consider an $SU(2)\times U(1)_Y\rightarrow U(1)_{EM}$ theory that is broken via a complex triplet with hypercharge 2. The potential is of the form \begin{align} V(\Phi) = -m^2\Phi^\dagger\Phi + \...
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479 views

$\rho$-parameters for several Higgs multiplets

I'm studying the Higgs mechanism of the spontaneus symmetry breaking in the SM. The expression for the $\rho$-parameter is $$ \rho=\frac{M^2_W}{{\cos^2\theta_w}M^2_Z}, $$ that, in the case of a $SU(2)...
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204 views

To what extent is the Standard Model vacuum made of a Bose-Einstein condensate of Higgs bosons?

Note: I very well understand spontaneous symmetry breaking of global symmetries and the Higgs mechanism. I want to know to what extent the Standard Model vacuum is made of a Bose-Einstein condensate ...
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306 views

How does the Higgs Particle Decay?

Background: It is my understanding that the Higgs Boson is a fluctuation of the Higgs field. It also is not very stable and decays into a plethora of other particles. If all other particles interact ...
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140 views

Were fermions ever massless?

In a discussion of the Standard model and Higgs mechanism it was claimed that accordingly: "During an early phase of the cosmos all fermions were massless." I wonder whether this claim can be ...
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181 views

Field content and symmetry groups of Minimal Composite Higgs Models

I'm trying to teach myself the Composite Higgs Model, both its theory and its LHC phenomenology (particularly the 4DCHM). Unfortunately, I'm struggling; the literature is contradictory and/or omits ...
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107 views

Higgs boson/field symmetries and local symmetries

In the SM with gauge group U(1)xSU(2)xSU(3), those factors are associated to the gauge bosons associated with a local symmetry and the Higgs field provides masses to the elementary fermions AND the W,...
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418 views

How is the hierarchy problem consistent with the decoupling theorem?

One the one hand we have the hierarchy problem in it's various forms, in my understanding in it's most serious form one could state it as the observation that if there is a heavy mass scale M in ...
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About the decay of Higgs into 2 Z bosons

I need to know if I understand this point. The factor of HZZ vertex in the SM Lagrangian is half the value of the Feynman rule which appears in Diagrammatica. When I calculate the decay of Higgs ...
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How Supersymmetry solves the hierarchy problem

The fermion contribution to the Higgs mass is $$\Delta m^2_{H}=-\frac{|\lambda_{f}|^2}{8\pi^2}\Lambda^2_{UV}+\dots$$ And the scalar contribution is: $$\Delta m^2_{H}=\frac{\lambda_{s}}{16\pi^2}\...
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Regularization methods' equivalence and the hierarchy problem

There are several questions related to this one but whose answers just raise the doubt I'm going to describe here. Some facts that are everywhere are (i) The hierarchy problem results from the fact ...
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55 views

Higgs amplitude mode vs. “spontaneous breaking” of local gauge symmetry

It seems that there are two definitions of the Higgs mode; one primarily used in particle theory, and one used in condensed matter. In the former, we can consider a simple Lagrangian of the form $$ \...
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How does one calculate branching ratio of Higgs particle decaying into virtual particle?

Very often when people talk about decay they use branching ratio to describe a particular decay channel, for example: $$Z\rightarrow e^{+}+e^{-}$$ If both Z and the electron and positon are one-...
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1answer
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Interpretation of a CLs exclusion plot

I have some trouble with the interpretation of this plot. The plot on the right shows the CLs values for the SM Higgs boson hypothesis as a function of the Higgs boson mass in the range 110–145 GeV. I ...
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How do we determine who eats who (or which field gets massive) in a Higgs phase transition?

Consider the following theory in which a $2$-form field $B_{\mu\nu}$ with field strength $P_{\alpha\mu\nu}=\partial_{[\alpha}B_{\mu\nu]}$ is coupled to a $3$-form gauge field $C_{\alpha\beta\gamma}$ ...
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1answer
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What happens to the massive gauge bosons in a simple Little Higgs model?

I'm trying to understand a simple Little Higgs (toy) model where the Higgs doublet is made of pseudo Nambu-Goldstone Bosons generated by breaking the symmetry from $SU(3)_L\times U(1)_Y$ to $SU(2)_L\...
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Higgs decay at higher energies

If I look at the expected Higgs decay BR's vs. $m_H$ the WW and ZZ dominate over the tt decay mode in the over tt threshold region. From the mere couplings: $g_{ffH} = \sqrt2 m_f /v$ $g_{VVH} = 2 ...
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Does Higgs field exert pressure which contributes to the stress-energy tensor causing gravity?

First of all, I have never studied quantum field theory. Since Higgs field is a scalar field, does Higgs field also exert positive/negative pressure which contributes to the stress-energy tensor ...
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Can Higgs mechanism happen in 1+1D?

How I understand the Higgs mechanism is that, although it is called “spontaneously breaking of the gauge symmetry”, the gauge symmetry is actually not broken in the higgs mechanism and it is the ...
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Virgin value of the Higgs field

https://profmattstrassler.com/articles-and-posts/particle-physics-basics/the-hierarchy-problem/naturalness/ According to Matt, the 246 GeV vev of the Higgs field came from: "We get these two ...
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1answer
239 views

Trying to work out the CP-transformation property of the Higgs potential

The parity transformation property of a complex scalar field $\phi(x)$ is given by: $$P\phi(t,\textbf{x}) P^{-1}=\eta_P\phi(t,-\textbf{x})$$ where $\eta_P=\pm 1$. The charge conjugation property of a ...
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1answer
149 views

Why is the term $\bar{L}\phi R$ invariant under $SU(2)_L \times U(1)_Y$ where $\phi$ is the Higgs field?

In the explanation for the fermion masses, the term $$\bar{L}\phi R$$ is added to the Lagrangian where $L$ is a left-handed $SU(2)$ doublet, $\phi$ is the Higgs left-handed $SU(2)$ doublet and $R$ is ...
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Why are the Weak force states different to the mass eigenstates?

On one hand we have the electro-weak interaction doublets $(u,d)$, $(c,s)$, $(e,\nu_e)$, etc. On the other hand, on the Yukawa interaction term that gives mass to fermions we have those same doublets. ...
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Is the Higgs vacuum expectation value scale-independent?

Like the title of the question states, I'd like to know if the Higgs vacuum expectation value is RG scale independent, or in other words, is it an observable. For instance, if we compute the position ...
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Is it interesting to ask why the Higgs vacuum expectation has its particular value?

By interesting, I mean more interesting than asking why any of the free parameters of the SM (electron mass, CP-violating phase, etc) have their particular values. The vacuum expectation value $\nu \...
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184 views

W-boson mass eigenstates after electroweak symmetry breaking

A question about how the physical $W^{\pm}_{\mu}, Z_{\mu}, A_{\mu} $ masses arise: We have the covariant derivative: $$ D_{\mu} = \partial_{\mu} - \frac{ig}{2}\begin{pmatrix} W^3 & \sqrt{2} w^+ \...
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54 views

Why does Higgs obtain certain values in SU(5) symmetry breaking?

In the SU(5) GUT model the symmetry is broken by a Higgs field with the element diag(2,2,2,-3,-3) taking a non-zero value. To break it down to SU(3)xSU(2)xU(1) But why exactly this element of all the ...
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What do people mean with a vev=diag( -2,-2,-2,-2,-2,-2,3,3,3,3)?

For example, in this paper on page 21 the authors write the vev that breaks $SO(10)$ to $SU(4)\times SU(2) \times SU(2)$ $$ <54>= 1/5 \cdot diag( -2,-2,-2,-2,-2,-2,3,3,3,3) \omega_s$$ where $\...