REVIEW
Mu Problem and Hybrid Inflation in Supersymmetric SU(2)_L x SU(2)_R x U(1)_B-L
High Energy Physics - Phenomenology · Submitted 10 Oct 1997 · 19 references
Pith's verdict: The singlet-does-everything construction is genuinely clever and checks out at leading order, but the vacuum selection and the deferred leptogenesis/inflation numbers are thinner than the abstract suggests.
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Referee report
The paper
The paper claims
A single singlet field in a left-right supersymmetric model is claimed to generate the MSSM mu parameter, its soft partner B mu, and a flat inflationary potential, all from one superpotential term.
The reading
What carries the argument
The load-bearing object is the gauge-singlet chiral superfield $S$ that appears in the superpotential only linearly, with an R-charge equal to that of the superpotential itself. Linearity is what makes the argument work in both directions: it guarantees that the inflaton potential is flat at tree level and that the one-loop Coleman-Weinberg correction is the only slope, and it guarantees that $S$ has no self-interactions to stabilize it at zero, so the tadpole proportional to $M^2$ from the soft terms displaces it by an amount fixed by $m_{3/2}$ rather than by $M$. The pseudo-Goldstone character of the Higgs doublets, following from an accidental $U(4)$ symmetry of the potential when $lambda = kappa$, is what keeps the doublets light and makes the generated $mu^2$ and $B mu$ automatically of the same order. The same R-symmetry whose $Z_2$ subgroup is ordinary matter parity also forbids the dimension-five operators that would let the proton decay, and the $l^c$ vev provides seesaw masses for right-handed neutrinos.
Extended reading notes
Core claim
The paper's central claim is that one renormalizable superpotential, $W = S(kappa l^c bar{l}^c + lambda h^2 - kappa M^2)$, does three jobs at once in a supersymmetric $SU(3)_c times SU(2)_L times SU(2)_R times U(1)_{B-L}$ model. First, the singlet $S$ triggers breaking of $SU(2)_R times U(1)_{B-L}$ at a scale $M$ far above the weak scale through the vacuum expectation values of the doublet pair $l^c, bar{l}^c$. Second, after gravity-mediated supersymmetry breaking the tadpole induced by that large vev shifts $S$ away from zero by roughly $-m_{3/2}/kappa$, so that $mu = lambda langle S rangle = -lambda m_{3/2}/kappa$ and $B mu = -2 lambda m_{3/2}^2/kappa$ come out of order the gravitino mass without any fine tuning of $M$; the Higgs doublets are pseudo-Goldstones of an approximate $U(4)$ symmetry of the scalar potential and stay massless until supersymmetry breaking lifts the flat direction. Third, for $|S| > max(M, M sqrt{kappa/lambda})$ all gauge non-singlet fields acquire masses of order $|S|$ and decouple, leaving an effective superpotential $W_{infl} = -kappa S M^2$ linear in $S$, hence a constant tree-level vacuum energy $V_{tree} = kappa^2 M^4$ and a one-loop logarithmic slope $V_{infl} simeq kappa^2 M^4 [1 + ((kappa^2+lambda^2)/8 pi^2) ln(S S^*/Lambda^2)]$ that drives the field to the minimum. Inflation ends when the condition on $|S|$ fails and some field goes tachyonic; the authors prefer $kappa < lambda$ so that the system falls to the $SU(2)_R$-breaking vacuum rather than to the one with large electroweak doublet vevs.
Load-bearing premise
The argument needs the universe to settle in the vacuum with $h = 0$ and $l^c bar{l}^c = M^2$; the paper shows the competing minimum with large electroweak doublet vevs is degenerate with it to leading order and can only be disfavoured by choosing a non-minimal Kaehler parameter with $|alpha|^2 geq lambda/kappa > 1$, justified by the single sentence that cosmological evolution prefers that choice, with no trajectory analysis given.
Editorial extensions
If this is right
- The MSSM $mu$ parameter stops being a free input: it is predicted as $mu = -lambda m_{3/2}/kappa$, of order the gravitino mass, with $B mu = -2 lambda m_{3/2}^2/kappa$, and the relation $mu^2 + m_{3/2}^2 = -B mu$ holds in the $U(4)$-symmetric limit $lambda = kappa$.
- The same sector that breaks $SU(2)_R times U(1)_{B-L}$ at scale $M$ is the inflaton sector, so the scale of new physics and the scale of inflation are tied together, with $V = kappa^2 M^4$ during the flat phase.
- The scalar spectral index comes out extremely close to unity, consistent with a mixed cold-plus-hot dark matter picture in which the hot component is a neutrino in the eV range.
- Baryogenesis proceeds through leptogenesis: the inflaton oscillations produce right-handed neutrinos whose decays create a lepton asymmetry, partially converted to baryon number by sphalerons, with the reheat temperature compatible with the gravitino bound.
- Proton decay from dimension-five operators is absent to all orders as long as the R-symmetry is exact in the superpotential, so the proton is essentially stable.
Reading between the lines
- Because $mu$ is generated by the same shift that sets the inflaton mass scale, a measurement pinning the inflaton coupling $kappa$ and $M$ would indirectly fix the ratio $lambda/kappa$ and hence the size of $B mu$; this cross-link is a testable correlation the paper does not spell out.
- The requirement $kappa < lambda$ is stated but not derived from the inflationary dynamics; a dedicated slow-roll analysis with the one-loop potential could turn it into a quantitative constraint on the $SU(2)_R$ breaking scale, which the paper only estimates as roughly an order of magnitude below the MSSM unification scale.
- The eV-scale neutrino hot dark matter component is the most externally checkable element: cosmological bounds on the sum of neutrino masses tighten the allowed window independently of any collider or proton-decay test of the $mu$ mechanism.
- The mechanism relies on gravity-mediated supersymmetry breaking to set the size of the shift; in a gauge-mediated version the displacement scale would change, so the claim that $mu$ comes out near the weak scale is tied to the mediation scheme rather than to the left-right structure alone.
Original abstract
We present a solution of the mu problem within a supersymmetric model based on the SU(2)_L x SU(2)_R x U(1)_{B-L} gauge group. We show that this solution implies a built-in hybrid inflationary scenario, which may result in a successful baryogenesis via leptogenesis. Baryon number is essentially conserved as a result of an R-symmetry. Neutrinos with mass in the eV range can provide the `hot' dark matter component.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
We present a solution of the mu problem within a supersymmetric model based on the SU(2)_L x SU(2)_R x U(1)_{B-L} gauge group. We show that this solution implies a built-in hybrid inflationary scenario, which may result in a successful baryogenesis via leptogenesis. Baryon number is essentially conserved as a result of an R-symmetry. Neutrinos with mass in the eV range can provide the `hot' dark matter component.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We present a solution of the mu problem within a supersymmetric model based on the SU(2)_L x SU(2)_R x U(1)_{B-L} gauge group. | contribution 1.00 | 0.94 | 0.46 | asserted 1.00 |
| s1 | We show that this solution implies a built-in hybrid inflationary scenario, which may result in a successful baryogenesis via leptogenesis. | interpretation 0.88 | 0.89 | 0.47 | hedged possibility 0.63 |
| s2 | Baryon number is essentially conserved as a result of an R-symmetry. | result 0.94 | 0.65 | 0.08 | asserted 1.00 |
| s3 | Neutrinos with mass in the eV range can provide the `hot' dark matter component. | result 0.66 | 0.42 | 0.06 | hedged possibility 0.73 |
What was examined, and what was not
- arXiv listing abstract v1
- full text
- figures and tables
- references and citing sentences
- relations to other papers
- P abstract
- S sections
- T body sentences
- C citations
- R cross-paper relations
References
How the literature uses it
38 arXiv papers cite this in 61 sentences
Papers whose main result relates to this one's
States the same result 1 paper
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The mu problem is solved, in this model, and the baryon asymmetry of the universe is produced through leptogenesis.
Papers citing it · 55 sentences without a confident label
Cites it as background 5 papers
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The form of these soft terms comes from gravity-mediated SUSY breaking [ref] , which we employ throughout.
Supersymmetric Hybrid Inflation Redux · Introduction · 0.80
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SUSY hybrid inflation [ref] provides fascinating framework to realize inflation within the grand unified theories (GUTs) of particle physics.
Radiative Symmetry breaking, Cosmic Strings and Observable Gravity Waves in $U(1)_R$ symmetric $SU(5) \times U(1)_{\chi}$ · Introduction · 0.96
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Reference [ref] , in particular, considered supersymmetric (SUSY) models based on the gauge group $SU(2)_L ×SU(2)_R ×U(1)_B-L$.
Testing Spontaneous Parity Violation at the LHC · Introduction · 0.85
Discussion
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