Probing String Theory with Modulated Cosmological Fluctuations

Lev Kofman

REVIEW

Probing String Theory with Modulated Cosmological Fluctuations

Lev Kofman

Astrophysics · Submitted 27 Mar 2003 · 17 references

Pith's verdict: A short, honest 2003 idea letter: the modulated-coupling mechanism is real and worth citing, but the amplitude rests on an uncomputed linear response of the reheat temperature to coupling variation in §IV.

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arXiv IDastro-ph/0303614 (version 2)

Pith IDPZNLE73L, Pith's permanent record of this paper and its review

CitationLev Kofman. "Probing String Theory with Modulated Cosmological Fluctuations." arXiv:astro-ph/0303614 (2003). https://pith.science/paper/PZNLE73L

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Editor's note

read the letter

Short version: this is a 2003 idea letter and should be read as one. Kofman's proposal is that light moduli and the dilaton, stretched to superhorizon scales during inflation, make coupling constants spatially variable, and that this variability modulates both freeze-out abundances and the reheat temperature. That gives you modulated isocurvature, and in the limiting case pure curvature perturbations with no contribution from inflaton fluctuations. The mechanism is the contribution, and it is genuinely distinct from the curvaton: the inflaton decays anyway, so no extra decay channel is needed. The freeze-out channel in §III is the part people forget, and it is a clean idea. The paper also cites the concurrent Dvali–Gruzinov–Zaldarriaga paper [17] rather than sitting on priority, which is decent behavior and not universal in this literature. Credit where due: it states the moduli problem up front and sets it aside explicitly, and it flags the Kähler tuning needed to keep moduli light. Those costs are acknowledged, not hidden. The soft spot is §IV, and the reader has it right. The chain δχ ~ H → δα/α → δT_r/T_r → ζ is textbook for the first two steps; the third is asserted. The paper says preheating is non-linear and the coupling dependence is “rather complicated” in its own words, citing [14], then says “on general grounds we still expect” linear response with an O(1) coefficient. That sentence carries the whole amplitude. The stress-test sharpening is fair: in parametric resonance the Floquet exponent is non-analytic in g²/λ, so the local slope d log T_r / d log g could be well above one or near zero, and nothing here distinguishes those cases. Also §IV writes the amplitude as ~δχ_a/χ_a, which is dimensionally loose; the honest expression is (∂ log α/∂χ)δχ, a second uncomputed coefficient. Minor: the title promises a probe of string theory, and the paper delivers a mechanism rather than an observational signature. Fine for a proceedings letter, worth saying anyway. Who should read it: anyone working on modulated reheating, curvaton-adjacent mechanisms, or moduli cosmology. It is a foundational reference for that literature. Send it to referees; the field publishes these, and this one is a legitimate mechanism proposal with its assumptions on the table.

Referee report

Significance

If the mechanism works, it is economical in a way worth noting: it needs no curvaton and no separate decay channel, since the inflaton decays anyway (§V), and it decouples the scalar amplitude from the shape of the inflaton potential, which is a genuine conceptual gain over standard inflationary model building. The proposal also has falsifiable structure that the paper could have exploited more: correlated curvature/isocurvature spectra (§III) and, as the referee notes below, a likely non-Gaussian signature. The author is candid about priority, stating in §V that Dvali, Gruzinov and Zaldarriaga independently suggested a similar curvature mechanism in ref. [17]. There are no machine-checked proofs, no code, and no parameter-free derivation here; the assessment therefore rests on the soundness of the argument chain, and the weakest link is quantitative rather than conceptual.

Major objections (3)

[§IV, final paragraph] The step that sets the amplitude of the entire curvature signal is asserted rather than derived. The text concedes that reheating proceeds through a non-perturbative, non-linear preheating stage and that the dependence of the reheat temperature on couplings is 'rather complicated' (citing [14]), and then writes: 'However, on general grounds we still expect that at large scales spatial variations in the final reheat temperature δT_r/T_r will be linear with respect to the couplings, δT_r/T_r ≃ δα/α.' The 'however, on general grounds' is carrying the whole quantitative claim of the paper. In parametric resonance the Floquet exponent is a non-analytic function of q = g²/λ, and backreaction and turbulence can saturate the sensitivity, so the local logarithmic slope d log T_r/d log g could plausibly be much larger than unity (overproducing curvature and non-Gaussianity) or close to zero (suppressing the mechanism below observability). The manuscript should supply at least a toy-model estimate of this slope — an analytic Floquet analysis in a single-resonance model, or a citation to a lattice study that measures T_r versus g — and should state explicitly the range of couplings for which the linear-response assumption is claimed to hold. A full lattice campaign is not required for a note of this length, but the coefficient cannot be left as an order-unity ansatz when it multiplies the headline number.
[§IV, paragraph 2] The amplitude of the modulated curvature fluctuations is written as '~ δχ_a/χ_a', which is dimensionally loose and obscures where the observed magnitude actually comes from. The correct expression following from Eq. (4) is ζ ~ (∂ log α/∂χ_a) δχ_a, and the paper should state this explicitly, together with the normalization it assumes for the derivative. For a string dilaton the derivative is naturally of order 1/M_P, which makes the H/M_P ~ 10⁻⁵ coincidence a genuine prediction rather than an accident; for a radion in a braneworld the same derivative carries warp-factor suppression, which would change the answer by many orders of magnitude. As written, the reader cannot tell whether the mechanism naturally reproduces the observed amplitude or whether an O(1) coefficient is being assumed. Please give the amplitude as an explicit formula with all coefficients displayed, and state for which class of moduli the H/M_P scaling is claimed.
[§III, Eq. (6)] The relation δρ/ρ ≃ δα/α for freeze-out and for baryon-number generation is quoted without derivation, and it is load-bearing for the isocurvature claim of abstract:s4. For thermal freeze-out the relic abundance scales as 1/⟨σv⟩, so δρ/ρ ≈ −δ⟨σv⟩/⟨σv⟩, which reduces to δα/α only if the annihilation cross section is dominated by a single gauge coupling with σ ∝ α² and no compensating dependence on masses or on g_*. For baryogenesis the sensitivity is more model-dependent still, since it depends on which coupling enters the CP-violating source and on the departure from equilibrium. The paper should work out at least one concrete example — neutralino freeze-out is the natural one, and is named in the text — and state the coefficient relating δρ/ρ to δα/α, including its sign. Without this, the isocurvature sector of the proposal is a plausibility statement rather than a prediction, and the interesting claim that curvature and isocurvature can be correlated (§III, final sentences) cannot be quantified.

Minor objections (11)

[§III, paragraph 2] The citation 'papers [ ?]' is an unresolved placeholder and must be completed before publication.
[§II, paragraph 3] The sentence 'For massive modes with m ≤ H the effect is absent' has the inequality reversed; the effect is absent for m ≫ H, which is what the surrounding discussion of the index λ = √(9/4 − m²/H²) implies.
[§III, paragraph 1] The freeze-out condition is stated backwards: 'their abundance is frozen out when the rate of their interaction with the hot plasma Γ begins to exceed the rate of expansion Γ > H'. Freeze-out occurs when Γ drops below H, so the inequality should read Γ < H.
[Eq. (1)] The moduli kinetic term is written as '½χ_aχ_a' with no derivatives; it should presumably read −½ ∂_μχ_a ∂^μχ_a. The same equation also appears to sum over a with an implicit index contraction that is not displayed.
[Eq. (5)] The one-loop coefficients are given as b_i = (33, 1, 3). Please check against the standard convention; in the MSSM with GUT normalization these are (33/5, 1, −3), and the sign of b₃ matters for the running described.
[§II, paragraph 2] The chain '<χ²> = ∫d³k|χ_k|² = ∫d³k/k³' is not dimensionally consistent as written; the second expression should be ∫dk/k up to numerical factors, and the normalization of Eq. (3) should be carried through explicitly.
[§II and §I] The phrases 'the outer space inflation' and 'the outer spacetime de Sitter geometry' are unclear; presumably the intended meaning is the observable 3+1 dimensional spacetime, and this should be stated once and used consistently.
[§V] The differentiation from ref. [17] should be made concrete rather than left as 'similar to ours'. A short paragraph stating what this paper adds beyond [17] — the freeze-out/isocurvature channel, the preheating channel, or both — would let the reader place the contribution.
[§IV and §V] There is no discussion of the expected non-Gaussianity. Modulated mechanisms of this type typically predict f_NL ≠ 0, and since the paper's selling point is a scalar spectrum detached from the inflaton potential, a sentence on the predicted level of non-Gaussianity (even an order-of-magnitude estimate) would strengthen the observational case considerably.
[Acknowledgments] The acknowledgment reads 'N. Kaloper and. Linde'; the second name is missing its initial.
[Throughout] There are numerous typographical errors that should be corrected: 'generatation' (§I), 'measurments' (§I), 'consituting' and 'assymetry' (§III), 'frezed out' (§III), 'illistrated' (§IV), and 'the casual horizon' (§I, for 'causal').

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The paper

The paper claims

Light moduli fields, not the inflaton, could be the source of cosmic density ripples: their superhorizon fluctuations would make the coupling constants vary from place to place, and those variations would imprint themselves on particleabund

The reading

Kofman asks whether the fields that set the strength of every interaction — the dilaton, moduli, radion — could leave a visible mark on the largest scales of the universe. If some of these fields are lighter than the Hubble scale during inflation, they acquire the same scale-free, superhorizon fluctuations as any other light scalar. Because coupling constants are the vacuum expectation values of these fields, the couplings themselves become spatially varying, $|da/a|$ of order $H/M_P$. Before the moduli settle into their minima, those variations shift the freeze-out time of relic species and the reheat temperature from patch to patch, so regions of the universe that are otherwise identical end up with slightly different energy densities. The interesting limit is that this can happen even if the inflaton's own fluctuations are switched off, in which case the entire observed curvature perturbation would be a secondary effect of varying couplings rather than a direct imprint of the inflaton potential.

What carries the argument

The mechanism is 'modulated fluctuations': a light scalar that is not the inflaton imprints its superhorizon spatial pattern onto the coupling constants, and the couplings then modulate local physics. The two channels the paper develops are (i) modulated isocurvature perturbations, where a spatially varying $alpha$ shifts the freeze-out time of CDM, baryons, or radiation and so gives $drho/rho ~ da/a$, and (ii) modulated curvature perturbations, where the same variation shifts the reheat temperature through the inflaton decay or preheating rate, $dT_r/T_r ~ da/a$, converting an entropy perturbation into an adiabatic one. In the second channel the inflaton's own quantum fluctuations can be made negligible, leaving curvature perturbations whose amplitude is controlled by the moduli sector and by $partial log a / partial chi$.

Extended reading notes

Core claim

The paper's central claim is that the spatial variation of coupling constants, inherited from light moduli during inflation, can generate scale-free curvature fluctuations on its own. The chain is: moduli lighter than $H$ freeze out at amplitude $dchi_k ~ H/sqrt{2k^3}$; the couplings inherit $da/a ~ (partial log a / partial chi) dchi ~ H/M_P$; species that freeze out or are produced by (p)reheating do so at slightly different times in different Hubble patches, giving $drho/rho ~ da/a$. Radiation isocurvature perturbations of this kind become curvature perturbations once radiation dominates, so the amplitude of the resulting scalar mode is tied to $H/M_P$ and to how the reheat temperature responds to the coupling, not to $V_{,phi}$ or the shape of the inflaton potential. Kofman presents this as a mechanism that is more economical than the curvaton, since the inflaton decays anyway and no extra decay channel has to be postulated.

Load-bearing premise

The whole curvature amplitude rests on the untested assertion that the reheat temperature responds linearly, with an order-one coefficient, to a spatial variation in the coupling constants, even though the paper itself notes that preheating is non-linear and that the dependence of $T_r$ on couplings is 'rather complicated'.

Editorial extensions

If this is right

The amplitude of the primordial scalar perturbation could be set by $H/M_P$ and by how couplings depend on moduli, with no sensitivity to the inflaton potential — a route to scale-free curvature perturbations that bypasses the usual slow-roll tuning.
Because the same moduli fluctuations feed both the curvature and the isocurvature channels, the two can be correlated, which is a distinctive signature rather than a generic prediction of single-field inflation.
Spatial variations of the coupling constants would be erased once the moduli are pinned to their minima, so the effect is confined to the early universe and shows up only through its imprint on relic abundances and reheating, not through present-day varying constants.
The mechanism also generates modulated isobaryonic and CDM isocurvature perturbations independently of curvature, giving a second observable channel if the relevant species freeze out early enough after inflation.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

The proposal makes a sharp, checkable statement about non-Gaussianity: if the curvature perturbation comes from a quadratic response to moduli fluctuations rather than from inflaton fluctuations, the bispectrum shape should differ from the single-field consistency-relation form, which is in principle separable with large-scale structure and CMB data.
The linear-response assumption could be tested directly by lattice simulations of preheating with a spatially modulated coupling, which would turn the order-one coefficient the paper assumes into a computed number and settle the amplitude question.
Because the moduli must be lighter than $H$ while the inflaton remains light too, the scenario sits in tension with minimal supergravity, where inflation generically gives all moduli masses of order $H$; the paper's escape is tuning the Kähler potential, so the mechanism's naturalness is tied to how that tuning is justified.
If the moduli decay late and gravitationally, the same spatial variations would also modulate the moduli decay rate, potentially leaving a correlated signature in the damping tail of the CMB that is not present in standard adiabatic inflation.

Original abstract

Superstring theory, models with extra dimensions and other SUSY models generically predict that the coupling constants are in fact vacuum expectation values of fields like the dilaton, moduli etc. Assuming some of these fields are light during inflation, we get generation of small classical inhomogeneities in these fields from inflation. Consequently, coupling constants inherit small inhomogeneities at scales much larger than the causal horizon in the early universe. After the moduli get pinned down to their minima, the spatial variations of coupling constants in the late time universe will be erased. However, inhomogeneities in coupling constants in the very early universe would generate modulated large scale fluctuations in all relic species that are produced due to interactions and freezing out. Moreover (p)reheating of the inflaton field results in modulated curvature fluctuations. Even if the standard inflaton fluctuations are suppressed, in this picture we may have pure curvature cosmological fluctuations entirely generated by the modulated spatial variations of the coupling constants during preheating.

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.

Compiled by classifier-1.13.0 via TypeSafe API, question bank abstract-p1-20260923, 2026-09-23: 1 request, 5,582 input tokens.

What the abstract itself states, as probabilities: claims first 0.03 · states limitation 0.25 · human participants 0.01 · controlled comparison 0.05 · randomized assignment 0.01 · states quantitative result 0.03 · compares with prior results 0.18 · mentions code or data availability 0.01.

The abstract, sentence by sentence

arXiv listing abstract v2. Results and the main claim are underlined; show every role.

Superstring theory, models with extra dimensions and other SUSY models generically predict that the coupling constants are in fact vacuum expectation values of fields like the dilaton, moduli etc. Assuming some of these fields are light during inflation, we get generation of small classical inhomogeneities in these fields from inflation. Consequently, coupling constants inherit small inhomogeneities at scales much larger than the causal horizon in the early universe. After the moduli get pinned down to their minima, the spatial variations of coupling constants in the late time universe will be erased. However, inhomogeneities in coupling constants in the very early universe would generate modulated large scale fluctuations in all relic species that are produced due to interactions and freezing out. Moreover (p)reheating of the inflaton field results in modulated curvature fluctuations. Even if the standard inflaton fluctuations are suppressed, in this picture we may have pure curvature cosmological fluctuations entirely generated by the modulated spatial variations of the coupling constants during preheating.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#	sentence	role	the authors' own work	states the main conclusion	strength
s0	Superstring theory, models with extra dimensions and other SUSY models generically predict that the coupling constants are in fact vacuum expectation values of fields like the dilaton, moduli etc.	background 1.00	0.04	0.03	asserted 0.80
s1	Assuming some of these fields are light during inflation, we get generation of small classical inhomogeneities in these fields from inflation.	result 0.37	0.16	0.04	asserted 0.74
s2	Consequently, coupling constants inherit small inhomogeneities at scales much larger than the causal horizon in the early universe.	result 0.65	0.21	0.08	asserted 1.00
s3	After the moduli get pinned down to their minima, the spatial variations of coupling constants in the late time universe will be erased.	background 0.42	0.12	0.05	asserted 0.99
s4	However, inhomogeneities in coupling constants in the very early universe would generate modulated large scale fluctuations in all relic species that are produced due to interactions and freezing out.	result 0.61	0.33	0.30	asserted 0.92
s5	Moreover (p)reheating of the inflaton field results in modulated curvature fluctuations.	result 0.76	0.27	0.11	asserted 0.99
s6	Even if the standard inflaton fluctuations are suppressed, in this picture we may have pure curvature cosmological fluctuations entirely generated by the modulated spatial variations of the coupling constants during preheating.	result 0.51	0.36	0.60	hedged possibility 1.00

What kind of paper the classifier reports this is: theoretical result 0.98 · evidence from argument 0.98.

What was examined, and what was not

sources read

arXiv listing abstract v2

not examined

full text
figures and tables
references and citing sentences
relations to other papers

levels run

P abstract

not run

S sections
T body sentences
C citations
R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

References

Works cited (17)

[17]

G. Dvali, A. Gruzinov, M. Zaldarriaga, “A new mechanism for gene rating density per- turbations from inﬂation”, [arXiv:astro-ph/0303591]. 8

View on Pith Pith review arXiv
[14]

G. N. Felder and L. Kofman, “The development of equilibrium afte r preheating,” Phys. Rev. D 63, 103503 (2001) [arXiv:hep-ph/0011160]; R. Micha and I. I. Tkache v, “Rela- tivistic turbulence: A long way from preheating to equilibrium,” arXiv:he p-ph/0210202

View on Pith Pith review arXiv 2001
[1]

V. F. Mukhanov and G. V. Chibisov, “Quantum Fluctuation And ’Non singular’ Uni- verse,” JETP Lett. 33, 532 (1981) [Pisma Zh. Eksp. Teor. Fiz. 33, 549 (1981)]; S. W. Hawking, “The Development Of Irregularities In A Single Bubble I nﬂationary Universe,” Phys. Lett. B 115, 295 (1982); A. A. Starobinsky, “Dynamics Of Phase Tran- sition In The New Inﬂationary ...

View on Pith 1981
[2]

A. Starobinsky, “Relic gravitational radiation spectrum and initia l state of the universe”, JETP Lett 30 (1979) 682

View on Pith 1979
[3]

ﬁrst reported in my plenary talk at Cosmo03, Chicago, Septembe r 2002; available at http://pancake.uchicago.edu/∼cosmo02/

View on Pith 2002
[4]

M. Dine, “Towards solution of the moduli problems of string cosmo logy”, [arXiv:hep- ph/0002047]

View on Pith
[5]

C. Csaki, M. L. Graesser and G. D. Kribs, “Radion dynamics and ele ctroweak physics,” Phys. Rev. D 63, 065002 (2001) [arXiv:hep-th/0008151]

View on Pith Pith review arXiv 2001
[6]

J. Polchinski, String Theory , vol.1, Cambridge University Press 1998

View on Pith 1998
[7]

G. N. Felder, L. Kofman and A. D. Linde, “Gravitational particle p roduction and the moduli problem,” JHEP 0002, 027 (2000) [arXiv:hep-ph/9909508]

View on Pith Pith review arXiv 2000
[8]

M. Dine, L. Randall and S. Thomas, “Supersymmetry breaking in t he early universe,” Phys. Rev. Lett. 75, 398 (1995) [arXiv:hep-ph/9503303]

View on Pith Pith review arXiv 1995
[9]

P. Langacker, G. Segre and M. J. Strassler, “Implications of ga uge uniﬁcation for time variation of the ﬁne structure constant,” Phys. Lett. B 528, 121 (2002) [arXiv:hep- ph/0112233]

View on Pith 2002
[10]

C. Gordon, D. Wands, B. A. Bassett and R. Maartens, “Adiaba tic and entropy pertur- bations from inﬂation,” Phys. Rev. D 63, 023506 (2001) [arXiv:astro-ph/0009131]

View on Pith Pith review arXiv 2001
[11]

C. L. Bennett et al. , “First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Preliminary Maps and Basic Results,” arXiv:astro-ph/ 0302207

View on Pith
[12]

L. Kofman, A. D. Linde and A. A. Starobinsky, Phys. Rev. Lett . 73, 3195 (1994) [arXiv:hep-th/9405187]

View on Pith Pith review arXiv 1994
[13]

L. Kofman, A. D. Linde and A. A. Starobinsky, “Towards the th eory of reheating after inﬂation,” Phys. Rev. D 56, 3258 (1997) [arXiv:hep-ph/9704452]

View on Pith Pith review arXiv 1997
[15]

D. H. Lyth and D. Wands, “Generating the curvature perturb ation without an inﬂaton,” Phys. Lett. B 524, 5 (2002) [arXiv:hep-ph/0110002]

View on Pith Pith review arXiv 2002
[16]

J. Garcia-Bellido, A. D. Linde and D. A. Linde, “Fluctuations of th e gravitational constant in the inﬂationary Brans-Dicke cosmology,” Phys. Rev. D 50, 730 (1994) [arXiv:astro-ph/9312039]

View on Pith Pith review arXiv 1994

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Non-Gaussianities in models with a varying inflaton decay rate
astro-ph 2003-05 accept novelty 6.0 of 10

Spatial variation in the inflaton decay rate generates local-type primordial non-Gaussianity with f_NL of order a few, far above the 10^-2 expected from single-field slow-roll inflation.
Suppressing the lower Multipoles in the CMB Anisotropies
astro-ph 2003-03 conditional novelty 6.0 of 10

A short kinetic-dominated stage at the onset of the last 65 e-folds of inflation can cut off primordial power at horizon scales, and WMAP temperature data prefer such a cutoff at roughly two sigma, not decisively.
Scale-dependent non-Gaussianity probes inflationary physics
astro-ph.CO 2010-07 accept novelty 5.5 of 10

The scale dependence of local-type bispectrum and trispectrum parameters is derived in the delta-N formalism, yielding new observables and consistency relations that separate single-field from multi-field inflation.
Exploring the Primordial Power Spectrum with Dark-Age 21 cm fluctuations
astro-ph.CO 2026-09 conditional novelty 5.0 of 10

Dark Ages 21 cm power-spectrum forecasts could constrain the spectral index runnings α_s and β_s roughly an order of magnitude tighter than Planck, enabling discrimination among inflation models degenerate in n_s and r.
Tachyonic Encore: A universal shift of inflationary observables
hep-th 2026-06 unverdicted novelty 5.0 of 10

A light axion spectator induces post-inflation tachyonic phases that produce a nearly scale-invariant boost to the curvature power spectrum and alter key inflationary observables in a largely potential-independent manner.
Stochastic Gravitational Waves from Modulated Reheating
astro-ph.CO 2025-10 unverdicted novelty 5.0 of 10

A spectator scalar in modulated reheating with large Higgs-like couplings generates detectable scalar-induced stochastic gravitational waves for BBO and DECIGO, but only outside perturbative low-energy extrapolations.
Type-III Seesaw in Non-Holomorphic Modular Symmetry and Leptogenesis
hep-ph 2025-08 unverdicted novelty 5.0 of 10

A Type-III seesaw model based on non-holomorphic modular symmetry fits NuFIT 6.0 neutrino data and produces baryogenesis via leptogenesis with Y_B-L about 1e-9.
Curvaton distribution from stochastic inflation
astro-ph.CO 2024-11 conditional novelty 5.0 of 10

Closed-form probability distributions for the curvature perturbation are derived for four exactly solvable curvaton potentials, and the mass-decay-rate parameter space is split into regions by the probability of produ...
Planck 2018 results. IX. Constraints on primordial non-Gaussianity
astro-ph.CO 2019-05 accept novelty 5.0 of 10

Planck 2018 temperature and polarization data constrain primordial non-Gaussianity to f_NL^local = -0.9 ± 5.1 and find no significant deviation from Gaussian initial conditions.
Primordial seeds of supermassive black holes
astro-ph.CO 2012-02 conditional novelty 5.0 of 10

Double inflation with a parametric-resonance feature generates a narrow peak in the density power spectrum that yields primordial black holes near 10^5 solar masses, proposed as seeds for supermassive black holes.
Formation of primordial black holes from non-Gaussian perturbations produced in a waterfall transition
astro-ph.CO 2011-12 conditional novelty 5.0 of 10

Requiring that the strongly non-Gaussian curvature perturbations from a hybrid-inflation waterfall not overproduce primordial black holes bounds the waterfall mass parameter to beta > 2.3, or beta > 1.65 for a higher ...
Non-Gaussianity, Spectral Index and Tensor Modes in Mixed Inflaton and Curvaton Models
astro-ph 2008-02 accept novelty 5.0 of 10

In mixed inflaton-curvaton models, large non-Gaussianity can coexist with an acceptable spectral index and tensor-to-scalar ratio, and a consistency relation links the bispectrum and trispectrum when the curvaton stay...
A note on Inflation and the Swampland
hep-th 2018-07 conditional novelty 4.0 of 10

The Swampland criteria do not conflict with inflation because the curvature perturbation may be generated by a spectator field rather than the inflaton, breaking the standard relation between the tensor-to-scalar rati...
Primordial black hole constraints for curvaton models with predicted large non-Gaussianity
astro-ph.CO 2013-03 conditional novelty 4.0 of 10

For a curvaton model whose curvature perturbation is the square of a Gaussian field, primordial black hole abundance limits push the power spectrum amplitude down to 10^-4 to 10^-2.5, up to two orders of magnitude bel...
CMBPol Mission Concept Study: Probing Inflation with CMB Polarization
astro-ph 2008-11 conditional novelty 4.0 of 10

A satellite measuring CMB B-mode polarization could detect primordial gravitational waves down to r about 0.002 and, if r exceeds 0.01, establish that inflation occurred near 10^16 GeV with a super-Planckian inflaton ...
Tilt and Tensor-to-Scalar Ratio in Multi-Scalar Field Inflation: Non-Sum-Separable Case
gr-qc 2024-12 reject novelty 3.0 of 10

A two-field chaotic inflation model with a kinetic-potential coupling can in principle lower ns and r, but the paper's analytic formulas miscompute the correction and its quoted parameter ranges are fitted rather than...
Inflation: Theory and Observations
astro-ph.CO 2022-03 accept novelty 3.0 of 10

The paper argues that three inflationary observables (tensor modes, non-Gaussianity, and primordial features) are the highest-value targets for the next decade, and quantifies the thresholds upcoming CMB, large-scale ...
Testing Inflation with Large Scale Structure: Connecting Hopes with Reality
astro-ph.CO 2014-12 conditional novelty 3.0 of 10

A workshop summary argues that future large-scale structure surveys can reach order-unity sensitivity to local and equilateral primordial non-Gaussianity, a level that would sharply test inflation models.
Introduction to Early Universe Cosmology
astro-ph.CO 2011-03 accept novelty 3.0 of 10

Cosmological perturbation theory applied to inflation, a matter bounce, and string gas cosmology shows all three can produce a scale-invariant spectrum, with distinguishable predictions in tensor tilt and non-Gaussianity.
Brane-World Gravity
hep-th 2010-04 accept novelty 3.0 of 10

Brane-world models recover four-dimensional gravity at low energies while predicting calculable, testable corrections at high energies, and this review consolidates their geometry, cosmology, and observational status.
Particle physics models of inflation and curvaton scenarios
hep-ph 2010-01 accept novelty 3.0 of 10

The review argues that inflatons and curvatons built from MSSM flat directions are the class most tightly tied to known particle physics, and therefore the class most likely to be falsified by CMB and collider data.
Cosmological perturbations
astro-ph 2008-09 accept novelty 3.0 of 10

A comprehensive review that organizes cosmological perturbation theory around gauge-invariant variables defined by physical coordinate choices, with explicit first- and second-order transformation rules and evolution ...
Nonperturbative Dynamics Of Reheating After Inflation: A Review
hep-ph 2014-10 accept novelty 2.0 of 10

The review synthesizes the nonperturbative physics of post-inflation reheating, from parametric preheating through nonlinear fragmentation and thermalization, and surveys models and observables.
Varying constants, Gravitation and Cosmology
astro-ph.CO 2010-09 accept novelty 2.0 of 10

The review argues that testing the constancy of the fundamental constants is a direct test of local position invariance and the universality of free fall, and catalogues every current observational constraint on such drift.
Local non-Gaussianity from inflation
astro-ph.CO 2010-04 accept novelty 2.0 of 10

Local primordial non-Gaussianity can be computed with the delta-N formalism and is predicted at potentially observable levels by curvaton, modulated reheating, and ekpyrotic models.
Review of local non-Gaussianity from multi-field inflation
astro-ph.CO 2010-02 accept novelty 2.0 of 10

Multi-field inflation can generate observable local non-Gaussianity, and the review states the analytic conditions for separable potentials, a slow-roll-free formalism, and an exact two-field solution.
Primordial Non-Gaussianities from Inflation Models
astro-ph.CO 2010-02 accept novelty 2.0 of 10

Different inflation mechanisms leave distinguishable shapes and runnings on the primordial bispectrum, making non-Gaussianity a probe of inflation dynamics.
TASI Lectures on Inflation
hep-th 2009-07 accept novelty 2.0 of 10

A complete, self-contained exposition of how a brief period of accelerated expansion solves the Big Bang's initial-condition problems and converts quantum vacuum fluctuations into the nearly scale-invariant scalar and...
Inflation Dynamics and Reheating
astro-ph 2005-07 accept novelty 2.0 of 10

A comprehensive review of multi-field inflation, reheating and preheating, and the curvaton and modulated-reheating alternatives for generating cosmic density perturbations, organized around a two-by-two transfer matr...
Inflation and String Theory
hep-th 2014-04 accept novelty 1.0 of 10

A survey arguing that inflation is ultraviolet-sensitive and therefore requires a quantum gravity completion, then cataloguing the string theory constructions that attempt to provide one.
Inflation, Cosmic Perturbations and Non-Gaussianities
hep-th 2013-03 accept novelty 1.0 of 10

A review that assembles the standard calculation of inflationary perturbations at linear and nonlinear order and surveys the model space with emphasis on non-Gaussian signatures.
Lectures on Reheating after Inflation
astro-ph.CO 2019-07 unverdicted

Lecture notes providing a generic introduction to reheating after inflation, covering its theoretical, phenomenological, and observational aspects.

How the literature uses it

137 arXiv papers cite this in 181 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 98 sentences without a confident label

Builds on it 1 paper

That way we can provide a new realization of modulated perturbations from reheating [ref] ; the decay rate of $χ$-particles depends on this coupling and the radion field value via $Γ∝h^2 ϕ$ [ref] .

Modulated Perturbations from Instant Preheating after new Ekpyrosis · Modulated Perturbations from Instant Preheating after Ekpyrosis · 0.80

Compares with it 2 papers

The contribution to the curvature perturbation through the modulation of the decay rate of the Q-balls is similar to the modulated reheating scenario [ref] .

Cosmic perturbations, baryon asymmetry and dark matter from the minimal supersymmetric standard model · Introduction · 0.92
Readers familiar with the literature may recognize that some ingredients of our scenario also appear in scenarios of modulated reheating [ref] and modulated preheating [ref] .

A Cosmic Microscope for the Preheating Era · Introduction · 0.82

Cites it as background 70 papers

For example, in the case of modulated reheating scenario [ref] , the inflaton decay width is determined by some light field $σ$ (called the modulon).

Cosmon as the Modulon: Non-Gaussianity from Dark Energy · Introduction · 0.90
This is the basic idea of the modulated reheating scenario [ref] to produce the curvature fluctuations in a way that is alternative to the standard mechanism.

Modulated Reheating and Large Non-Gaussianity in String Cosmology · Non-gaussianity · 0.95
Here, we give a brief review of the modulated reheating scenario [ref] .

Affleck-Dine baryogenesis with modulated reheating · Modulated reheating scenario · 1.00

Discussion

Disagree with the review, or know something it missed? Leave a comment, highlight any passage above to comment on it, or challenge this review formally.

[1] [17]

G. Dvali, A. Gruzinov, M. Zaldarriaga, “A new mechanism for gene rating density per- turbations from inﬂation”, [arXiv:astro-ph/0303591]. 8

View on Pith Pith review arXiv

[2] [14]

G. N. Felder and L. Kofman, “The development of equilibrium afte r preheating,” Phys. Rev. D 63, 103503 (2001) [arXiv:hep-ph/0011160]; R. Micha and I. I. Tkache v, “Rela- tivistic turbulence: A long way from preheating to equilibrium,” arXiv:he p-ph/0210202

View on Pith Pith review arXiv 2001

[3] [1]

V. F. Mukhanov and G. V. Chibisov, “Quantum Fluctuation And ’Non singular’ Uni- verse,” JETP Lett. 33, 532 (1981) [Pisma Zh. Eksp. Teor. Fiz. 33, 549 (1981)]; S. W. Hawking, “The Development Of Irregularities In A Single Bubble I nﬂationary Universe,” Phys. Lett. B 115, 295 (1982); A. A. Starobinsky, “Dynamics Of Phase Tran- sition In The New Inﬂationary ...

View on Pith 1981

[4] [2]

A. Starobinsky, “Relic gravitational radiation spectrum and initia l state of the universe”, JETP Lett 30 (1979) 682

View on Pith 1979

[5] [3]

ﬁrst reported in my plenary talk at Cosmo03, Chicago, Septembe r 2002; available at http://pancake.uchicago.edu/∼cosmo02/

View on Pith 2002

[6] [4]

M. Dine, “Towards solution of the moduli problems of string cosmo logy”, [arXiv:hep- ph/0002047]

View on Pith

[7] [5]

C. Csaki, M. L. Graesser and G. D. Kribs, “Radion dynamics and ele ctroweak physics,” Phys. Rev. D 63, 065002 (2001) [arXiv:hep-th/0008151]

View on Pith Pith review arXiv 2001

[8] [6]

J. Polchinski, String Theory , vol.1, Cambridge University Press 1998

View on Pith 1998

[9] [7]

G. N. Felder, L. Kofman and A. D. Linde, “Gravitational particle p roduction and the moduli problem,” JHEP 0002, 027 (2000) [arXiv:hep-ph/9909508]

View on Pith Pith review arXiv 2000

[10] [8]

M. Dine, L. Randall and S. Thomas, “Supersymmetry breaking in t he early universe,” Phys. Rev. Lett. 75, 398 (1995) [arXiv:hep-ph/9503303]

View on Pith Pith review arXiv 1995

[11] [9]

P. Langacker, G. Segre and M. J. Strassler, “Implications of ga uge uniﬁcation for time variation of the ﬁne structure constant,” Phys. Lett. B 528, 121 (2002) [arXiv:hep- ph/0112233]

View on Pith 2002

[12] [10]

C. Gordon, D. Wands, B. A. Bassett and R. Maartens, “Adiaba tic and entropy pertur- bations from inﬂation,” Phys. Rev. D 63, 023506 (2001) [arXiv:astro-ph/0009131]

View on Pith Pith review arXiv 2001

[13] [11]

C. L. Bennett et al. , “First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Preliminary Maps and Basic Results,” arXiv:astro-ph/ 0302207

View on Pith

[14] [12]

L. Kofman, A. D. Linde and A. A. Starobinsky, Phys. Rev. Lett . 73, 3195 (1994) [arXiv:hep-th/9405187]

View on Pith Pith review arXiv 1994

[15] [13]

L. Kofman, A. D. Linde and A. A. Starobinsky, “Towards the th eory of reheating after inﬂation,” Phys. Rev. D 56, 3258 (1997) [arXiv:hep-ph/9704452]

View on Pith Pith review arXiv 1997

[16] [15]

D. H. Lyth and D. Wands, “Generating the curvature perturb ation without an inﬂaton,” Phys. Lett. B 524, 5 (2002) [arXiv:hep-ph/0110002]

View on Pith Pith review arXiv 2002

[17] [16]

J. Garcia-Bellido, A. D. Linde and D. A. Linde, “Fluctuations of th e gravitational constant in the inﬂationary Brans-Dicke cosmology,” Phys. Rev. D 50, 730 (1994) [arXiv:astro-ph/9312039]

View on Pith Pith review arXiv 1994