Enhanced symmetries and the ground state of string theory

Dine, Michael; Nir, Yosef; Shadmi, Yael

doi:10.1016/s0370-2693(98)00975-7

Cited by 33 publications

(54 citation statements)

References 17 publications

(25 reference statements)

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“…Another possibility is if signigicant energy is not stored in the fields. This could be accomplished by dynamics, or if the moduli are stabilized initially near points of enhanced symmetry [8,9]. However, in this case, the need for a perturbative low energy theory necessarily requires at least one modulus to remain unprotected, and thus a substantial contribution to the energy density should still be expected [9].…”

Section: Introductionmentioning

confidence: 99%

Nonthermal “WIMP miracle”

Acharya

Kane²,

Watson³

et al. 2009

Phys. Rev. D

163

170

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Light scalar fields with only gravitational strength couplings are typically present in UV complete theories of physics beyond the Standard Model. In the early universe it is natural for these fields to dominate the energy density, and their subsequent decay -if prior to BBN -will typically yield some dark matter particles in their decay products. In this paper we make the observation that a Non-thermal WIMP 'Miracle' may result: that is, in the simplest solution to the cosmological moduli problem, non-thermally produced WIMPs can naturally account for the observed dark matter relic density. Such a solution may be generic in string theory compactifications.

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Section: Introductionmentioning

confidence: 99%

Nonthermal “WIMP miracle”

Acharya

Kane²,

Watson³

et al. 2009

Phys. Rev. D

163

170

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show abstract

“…Indeed, as we will show, the branching a See Refs. [3,4] for other solutions. ratio of the modulus decay into the gravitino is generically quite large…”

mentioning

confidence: 99%

Moduli-Induced Gravitino Problem

2006

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We investigate the cosmological moduli problem by studying a modulus decay in detail and find that the branching ratio of the gravitino production is generically of O(0.01 − 1), which causes another cosmological disaster. Consequently, the cosmological moduli problem cannot be solved simply by making the modulus mass heavier than 100 TeV. We also illustrate our results by explicitly calculating the branching ratio into the gravitinos in the mixed modulus-anomaly/KKLT-and racetrack-type models.The cosmological moduli problem [1] is one of the most challenging puzzles in particle physics and cosmology. In this letter, we show that the problem is even more difficult than usually thought.In supergravity/superstring theories, generically there exist moduli fields which have flat potentials and obtain masses from supersymmetry (SUSY) breaking and nonperturbative effects. During an inflationary period, a modulus field X is likely to develop a large expectation value. After the end of the inflation, it starts a coherent oscillation and soon dominates the energy density of the universe. Due to the interaction suppressed by the Planck scale M P = 2.4 × 10 18 GeV, the decay rate of the modulus X is extremely small:which leads to an onset of a radiation-dominated universe with a very low temperature:Here, c is an order one coefficient and g * is the effective number of massless degrees of freedom. This is cosmologically unacceptable because a successful big-bang nucleosynthesis (BBN) requires that the (last) radiationdominated universe starts with temperature higher thanAs is clear from Eq. (2), a simple solution would be to assume that the modulus X is ultra heavy a :Actually, there have been proposed scenarios with such a large modulus mass (cf. [5,6,7,8,9]). However, there exists yet another serious cosmological obstacle even for heavy moduli scenarios. The new problem is caused by the gravitino which is produced by the modulus decay. Indeed, as we will show, the branching a See Refs. [3,4] for other solutions. ratio of the modulus decay into the gravitino is generically quite largewhich causes serious problems after the modulus decay. We call this problem the moduli-induced gravitino problem.The gravitino production via modulus decay and its cosmological implications have been previously discussed in Refs. [10,11], taking Br(X → gravitino) ≪ 1. The main purpose of this letter is to show that Eq. (4) holds in a generic setup, and to emphasize how disastrous its consequences are. We also exemplify explicit results in the mixed modulus-anomaly/KKLT mediation [6,7] and in the racetrack [8] setups.Let us first estimate the branching ratio of a modulus decay into gravitino(s). We consider a heavy modulus scenario, m X > ∼ 100 TeV [cf. Eq. (3)]. On the other hand, the gravitino is likely to be (much) lighter than 100 TeV, because too large gravitino mass requires a finetuning in the Higgs sector due to the anomaly-mediated effects. Thus, we assume m X ≫ m 3/2 hereafter. After choosing the unitary gauge in the Einstein frame, w...

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“…The energy of axions at present is denoted by E 0 , which is assumed to be much 4 In this case, we expect large soft masses as the gravitino mass and hence one needs large coefficients in the Giudice-Masiero terms or many light Higgs fields through a fine-tuning.…”

Section: Axion-photon Conversion In the Early Universementioning

confidence: 99%

“…It is expected that axionic dark radiation is produced through the lightest modulus decay because the axions are coupled to the lightest modulus in their kinetic terms [12,13]. 4 Lastly let us mention the related works in the past. The conversion of CMB into the axion in the primordial magnetic field and resulting constraints were studied in Refs.…”

Section: Introductionmentioning

confidence: 99%

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Cosmological constraints on axionic dark radiation from axion-photon conversion in the early Universe

Higaki

Nakayama

Takahashi

2013

J. Cosmol. Astropart. Phys.

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Axions seem ubiquitous in string theories and some of them may be produced non-thermally by heavy scalar decays, contributing to dark radiation. We study various cosmological effects of photons produced from the axionic dark radiation through axion-photon conversion in the presence of primordial magnetic fields, and derive tight constraints on the combination of the axion-photon coupling and the primordial magnetic field.

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Enhanced symmetries and the ground state of string theory

Cited by 33 publications

References 17 publications

Nonthermal “WIMP miracle”

Nonthermal “WIMP miracle”

Moduli-Induced Gravitino Problem

Cosmological constraints on axionic dark radiation from axion-photon conversion in the early Universe

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