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Results tagged with beyond-the-standard-model
Search options questions only
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user 37286
Use this tag for questions beyond the standard laws of physics (General Relativity and the Standard Model) if a more specific tag, like "string-theory", "loop-quantum-gravity", "supersymmetry", etc. do not apply.
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Why is $\sqrt{v_1+v_2+\ldots} =246$ GeV in multi-Higgs models?
Where does the condition come from that in models with several electroweak breaking doublets the square root of the squared sum of the VEVs should yield $246$ GeV?
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0
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Why is the tensor product $n \otimes n = 1$ for $SO(n)$ not the usual scalar product?
For concreteness let's consider $SO(4)$.
The quantum numbers for the four states in the fundamental representations are (schematically)
$$ (1, 1) ,(-1, 1) ,(1, -1) ,(-1, -1 )$$
thus
$$ 4= \be …
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2
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0
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What do people mean with a vev=diag( -2,-2,-2,-2,-2,-2,3,3,3,3)?
For example, in this paper on page 21 the authors write the vev that breaks $SO(10)$ to $SU(4)\times SU(2) \times SU(2)$
$$ <54>= 1/5 \cdot diag( -2,-2,-2,-2,-2,-2,3,3,3,3) \omega_s$$
where $\omega_ …
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3
votes
1
answer
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One-Loop Yukawa RGEs
I'm currently trying to understand how one can write the one-loop RGEs for the Yukawa couplings using the general formula:
One example I'm interested in is how the author derives, using this formul …
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6
votes
1
answer
162
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Where does the matching condition for $U(1)$ subgroups come from in unified models?
The matching conditions for a breaking $G \rightarrow \prod_i G_i$ are
$$\omega_G-\frac{C_2(G)(\mu)}{12 \pi}=\omega_{G_i}-\frac{C_2(G_i)(\mu)}{12 \pi} ,$$
where $C_2(g)$ denotes the quadratic Casimi …
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3
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1
answer
343
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Can a symmetry breaking VEV lie far above the "symmetry breaking scale?"
The scale where some symmetry gets broken can be computed using the renormalization group equations for the gauge couplings. If there is only one Higgs VEV responsible for some breaking, can this VEV …
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2
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1
answer
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How can we calculate the PMNS matrix in general?
If we only introduce Dirac mass terms for neutrinos, we have analogous to the quark mass matrices, a normal $3 \times 3$ neutrino mass matrix $M_\nu$, written in the basis: $(\nu_L^1,\nu_L^2,\nu_L^3)M …
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0
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0
answers
117
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Which representation do we start with in Grand Unified Theories?
The conventional approach in GUTs is to put all left-chiral fields $F_L$ of the standard model into one representation of the GUT group. For example, the 16 rep for $SO(10)$ GUT:
$$ 16_L \rightarrow …
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5
votes
2
answers
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Why do decompositons like $16 \otimes 16 = 10 \oplus 120 \oplus 126$ tell us which Higgs rep...
EDIT: I found an answer, which I do not understand: In Gürsey - Symmetry breaking patterns in E6 he writes: " Because of Fermi-Dirac statistics of fermions they must occur in the symmetric part of 27x …
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0
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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 unders …
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1
vote
1
answer
459
views
The deSitter group vs. the Poincare group for a non-zero cosmological constant?
The present experimental value for the cosmological constant is tiny, but nonzero: $\Lambda \approx 1.19·10^{−52}$ $1/m^2$.
The Poincare group is the contraction of the deSitter group in the limit $ …
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2
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1
answer
346
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1-Loop Mass Splitting of vector-like Fermions
In this paper the author argues that for a vector-like fermion doublet, with degenerate mass $M$ at tree level, we always have a mass splitting between the charged component of the doublet $L$ and the …
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1
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0
answers
71
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Is it possible that are particle is much heavier through a loop correction?
Let's assume, we have standard model singlet particle $s$, that mixes after electroweak symmetry breaking with an exotic, vectorlike neutral lepton $N$. The relevant part of the Lagrangian reads
$$ L …
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1
answer
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Why does the electromagnetic and weak coupling strength do not meet at the electroweak scale?
The running of the coupling strengths is usually visualized on a logarithmic scale like here
What surprises me is that the weak and the electromagnetic coupling strength do not meet before the GUT …
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1
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1
answer
458
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Correct Yukawa Term with a SU(2) Higgs Triplet?
Given $SU(2)$ doublet fermions $\Psi^1$ and $\Psi^2$ and a $SU(2)$ triplet Higgs $H$, how does the correct Yukawa term look like in tensor notation?
Schematically, we have
$$ 2 \otimes 2 \otimes 3 …
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