Pith. sign in

REVIEW 1 major objections 6 minor 59 references

Instant Cosmology

T0 review · 1 major / 6 minor · reviewed 2026-08-11 · deepseek-v4-flash

Challenge this review Re-run · record.json Download PDF Read on arXiv ↗ Review JSON

Pith's one-line read A gas of Instant Folded Strings can be integrated out to yield an expanding universe whose dark energy comes from the slope of the dilaton potential.

desk verdict A coherent and honest speculative proposal whose new slow-roll machinery is internally consistent, but the load-bearing FRW pressure ansatz is unproven and everything downstream inherits that uncertainty. read the letter →

arxiv 2412.02630 v2 pith:2PRLGLID submitted 2024-12-03 hep-th

Nissan Itzhaki , Uri Peleg This is my paper · ORCID
classification hep-th
keywords InstantFoldedStringsnullenergyconditionviolationdilatoncosmologyslow-rollinflationDine-Seibergproblemcosmologicalconstantbouncingdark
topics Dark Energy
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

The paper argues that a homogeneous gas of Instant Folded Strings (IFSs) -- light, extended strings produced when the string coupling increases with time -- can be integrated out in an expanding universe whenever the string coupling is much larger than the Hubble rate, $g_s \gg H$. The gas exerts a negative pressure $p_{\rm IFS}=-\gamma/(3g_s^4)(\partial\phi)^2\Theta(\dot\phi)$, which violates the null energy condition but is suppressed by the Bianchi identity during expansion. The resulting friction drives the dilaton to a slow-roll attractor for generic potentials, so the expansion is governed by an effective potential $V_{\rm eff}=V-V'/\sqrt{8\kappa}$. If this holds, inflation needs no potential engineering, the Dine-Seiberg dilaton runaway is halted by IFS friction, a one-loop cosmological constant of the form $V^{(1)}=C\Lambda^4 e^{\sqrt{8\kappa}\phi}$ cancels exactly, and contraction naturally produces bounces.

What carries the argument

The central object is an Instant Folded String: a closed folded string created classically in a single instant when the dilaton rolls toward stronger coupling, whose bulk carries positive tension energy and whose folds carry compensating negative energy, making the gas violate the NEC while contributing no net energy in the linear-dilaton background. The load-bearing mechanism is the pressure formula $p_{\rm IFS}=-\gamma/(3g_s^4)(\partial\phi)^2\Theta(\dot\phi)$ combined with the Bianchi identity for the gas, which converts the negative pressure into an $H$-independent damping term in the dilaton equation. That friction generates the attractor of Appendix B: any state with $\dot\phi>0$ reaches $\dot\phi_{\rm SR}=g_s\sqrt{-[V'(\phi)+\rho_m]/(\sqrt{2}\kappa\gamma)}$ within a time of order $g_s^{-1}H^{-1}$, so $\dot\phi/H\sim g_s$ and the dilaton is effectively frozen on the Hubble time. The output is the effective potential $V_{\rm eff}=V-V'/\sqrt{8\kappa}$ and a shifted radiation term, with the unknown order-one coefficient $\gamma$ dropping out of the slow-roll attractor.

What would settle it

The decisive check is an exact or controlled numerical computation of the IFS contribution to the energy-momentum tensor in an FRW background with time-dependent dilaton in the regime $g_s\gg H$, comparing the coefficient of $(\partial\phi)^2$ in the pressure with $-\gamma/(3g_s^4)$ and its $H$-dependence with the Bianchi-identity result. Any deviation in the $\dot\phi$-dependence, $g_s$-dependence, or $H$-dependence would change Eq. (3.7), and with it $V_{\rm eff}$, the inflation, the one-loop cancellation, and the bounce.

Watch

Extended reading notes

Core claim

The central claim is that IFSs, though light and extended, can be integrated out in the regime $g_s \gg H$ to give closed effective equations for the scale factor $a(t)$ and dilaton $\phi(t)$, namely Eq. (3.7). The IFS pressure is $p_{\rm IFS}=-\frac{\gamma}{3g_s^4}(\partial\phi)^2\Theta(\dot\phi)$, with no energy density in the exactly time-translation-invariant linear-dilaton background; in FRW the Bianchi identity supplies the energy density and makes it grow during expansion, diluting the NEC violation. Equation (3.7b) acquires an $H$-independent friction term proportional to $\dot\phi^2/g_s^2$ that is largest at weak coupling, so generic potentials with $V'<0$ converge to the slow-roll relation $V'\simeq -(\kappa\gamma/\sqrt{2})\dot\phi^2/g_s^2$. At the attractor, the Friedmann equation becomes $3H^2\simeq \kappa^2(V_{\rm eff}+\rho_{\rm eff-rad})$ with $V_{\rm eff}=V-V'/\sqrt{8\kappa}$, the extra term being positive when $V'<0$. The paper then uses this effective potential to argue that inflation is generic, that a negative $V$ can appear as positive $V_{\rm eff}$ (an AdS-to-dS uplift), that the dilaton is pseudo-stabilized, that a one-loop cosmological constant of exponential dilaton dependence is exactly cancelled, and that bouncing solutions $a(t)\propto\cosh^{1/4}(t)$ exist in contraction.

Load-bearing premise

The load-bearing premise is that the IFS pressure law measured in the time-like linear dilaton background, $p_{\rm IFS}=-\gamma/(3g_s^4)(\partial\phi)^2\Theta(\dot\phi)$, continues to hold in a general FRW background with a time-dependent dilaton, since the paper lacks the exact IFS solution and exact CFT description there and extends the production rate by analogy.

Editorial extensions

If this is right

  • For generic potentials with $V'<0$ and weak coupling, the equation of state of the effective dark energy is $w=-1+\mathcal{O}(g_s)$, automatically near $-1$, and can cross below $-1$ because of the NEC-violating IFS contribution.
  • Inflation in this setup requires no tuning of the potential and no special initial conditions: any $\dot\phi>0$ is dragged onto the attractor, and there is no graceful-exit problem because the slow-roll conditions fail near the minimum of $V$.
  • The dilaton is pseudo-stabilized at weak coupling: IFS friction is independent of $H$ and strongest when $g_s$ is small, so a rolling dilaton barely moves over a Hubble time, offering a resolution of the Dine-Seiberg problem in the $\dot\phi>0$ branch.
  • A one-loop cosmological constant $V^{(1)}=C\Lambda^4 e^{\sqrt{8\kappa}\phi}$ with $C<0$ is exactly cancelled by the $V'$ piece, leaving dark energy of order $g_s^2\Lambda^4_{\rm SUSY}$; matching observation would require $g_s\sim10^{-30}$, too small unless combined with large extra dimensions or warped geometries.
  • In a contracting universe the effective radiation density can be negative while $V_{\rm eff}>0$, producing the exact bouncing solution $a(t)\propto[\cosh(\kappa\sqrt{12V_{\rm eff}}(t-t_b))]^{1/4}$.

Reading between the lines

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

  • If an exact IFS solution in FRW confirms Eq. (3.5), the structure $V_{\rm eff}=V-V'/\sqrt{8\kappa}$ is essentially a Legendre transform of the potential; such transforms typically signal an underlying constraint or duality, so one might expect the effective theory to have a hidden shift symmetry that also protects the residual dark energy at higher loops.
  • The $\beta$-dependent screening of matter, where the gravitational matter density is rescaled by $(1-\beta)$, suggests a testable extension: in inhomogeneous settings this should generate a scale-dependent effective gravitational coupling or equivalence-principle violations, potentially distinguishing the scenario from cold dark matter.
  • The paper's one-loop cancellation is strongly reminiscent of conformal-symmetry-based proposals for the cosmological constant; if IFSs are the microscopic realization, the same mechanism may apply to other light instant objects such as folded D-branes that couple to other moduli, connecting moduli stabilization to the swampland program.
  • A concrete next step the paper leaves implicit is to compute the primordial spectrum generated during instant inflation, since the decay products include null modes with $E\sim-1/g_s$; such modes could leave distinguishable non-Gaussian or isocurvature signatures not present in slow-roll inflation.
Share X Bluesky LinkedIn Reddit HN

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

1 major / 6 minor

Summary. The paper proposes a new cosmological scenario driven by Instant Folded Strings (IFSs), which appear when the string coupling increases with time. The authors extrapolate the linear-dilaton IFS pressure (2.7) to a general FRW background as p_IFS = -γ/(3 g_s^4) (∂φ)^2 Θ(φ̇) (Eq. 3.5), and, using the Bianchi identity, derive the effective equations of motion (3.7). In the slow-roll regime (Appendix B) they obtain an effective dark energy V_eff = V - (1/√(8κ)) V' (Eq. 4.8), leading to claims of generic inflation without potential tuning, a resolution of the Dine–Seiberg problem via IFS friction, an exact one-loop cancellation of the cosmological constant (Eq. 5.12), and generic bounces in contraction (Eq. 6.8). The paper also discusses matter screening (Eq. 5.9) and potential observational imprints.

Significance. If the assumed pressure form (3.5) is correct, the paper opens a genuinely new avenue in string cosmology: it provides a concrete, weakly coupled mechanism whereby the dilaton's slope rather than its value sources dark energy, and it gives specific predictions—such as w < -1 with corrections of order g_s, gravitational rescaling of matter by (1-β), and the generic occurrence of bounces—that could be tested against future cosmological observations. The paper is also commendably transparent: it explicitly states in Sec. 3 that the exact IFS solution and CFT description in FRW are unknown, that the production rate (3.4) is an analogy, and in Sec. 4.1 that fluctuation calculations require a better understanding of IFS decay. However, the significance is conditional: all subsequent results are algebraic consequences of (3.5) plus the Bianchi identity, so the extrapolation is the entire load-bearing premise. The paper does not yet provide a derivation of (3.5) or a quantitative bound on its corrections, and several headline claims (CC cancellation, Dine–Seiberg resolution, bouncing naturalness) are proofs of principle rather than established mechanisms.

major comments (1)
  1. [Sec. 6, Eq. (6.8)] The bouncing solution (6.8) requires negative effective radiation density ρ* < 0. While the V' contribution to ρ* can be negative when V' < 0, the paper does not discuss whether the initial condition ρ_r(t=0) + V'/√(8κ) < 0 is natural or how it is set by the IFS gas production. Since the authors themselves note in Sec. 3 that ρ_IFS need not vanish in FRW, a more careful treatment of the initial energy budget is needed before one can claim that bounces are 'a natural and prevalent outcome.'
minor comments (6)
  1. [Throughout] There are several typographical inconsistencies in the notation for κ: in Eqs. (4.5)–(4.9), (5.6), (5.9), (6.3), and (6.6), the symbol 'k' appears where 'κ' is clearly intended (e.g., 'ρr(t) = -1/√(8κ) V' but then '1/√(8k) V''). Please correct these.
  2. [Sec. 2, first paragraph] The phrase 'time-like linear dialton' contains a typo; it should read 'time-like linear dilaton.'
  3. [Sec. 3, after Eq. (3.7)] The text states 'we also rescaled γ → 2γ/κ² for convenience,' but the subsequent equations use γ without explicitly reminding the reader of this rescaling. Please add a note in the text to avoid confusion when comparing (3.5) with (3.7b) and later equations.
  4. [Appendix A, around Eq. (A.8)] The acronym 'FLRW' is written as 'FLR W' twice; this is a typographical error.
  5. [Sec. 4.1, Eq. (4.10)] The null mode energy is written as E ∼ -1/g_s with P = ±E. As written, the sign of P relative to E is ambiguous; please specify that the two modes have P = -E and P = +E, respectively, or clarify the convention.
  6. [Sec. 5.1] The phrase 'an approximated dS' should be 'an approximate dS' or 'an approximated dS space' (grammar).

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the paper's results are conditional consequences of a stated pressure ansatz, with no fitted parameter renamed as a prediction.

full rationale

The derivation chain begins with an explicit extrapolation, Eq. (3.5), for the IFS pressure in an FRW background: p_IFS = -(gamma/(3 g_s^4)) (partial phi)^2 Theta(phi-dot). The authors openly state that they lack an exact IFS solution and an exact CFT description in the FRW background, and that the production rate (3.4) is 'expected by analogy.' Everything downstream -- the Bianchi-identity closure (3.6), the effective equations (3.7), the slow-roll attractor (4.2), the effective potential V_eff = V - V'/sqrt(8 kappa) (4.8), the one-loop cancellation (5.12), the matter rescaling (5.9), and the bounce (6.8) -- is a direct algebraic consequence of this assumed pressure form. That makes the results conditional on the ansatz, but not circular: no parameter is fitted to the quantities being 'predicted,' the undetermined constant gamma drops out of the slow-roll results, and the one-loop cancellation is a concrete exponential identity rather than a tautology imposed by tuning V_eff. The self-citations to [1,3-6] supply the input IFS properties from prior published work, but those properties are not defined in terms of the present paper's conclusions, nor is any uniqueness theorem from the authors invoked to forbid alternatives. The main concern is the legitimacy of the extrapolation (3.5), which is a scientific-risk issue about an unproven assumption, not a circularity.

Assumptions & free parameters 4 free parameters · 6 assumptions · 2 invented entities

The central derivation rests on an assumed pressure formula for IFSs in FRW, an estimated production rate, a quick-decay hypothesis, and an unusual validity condition g_s >> H. One order-one constant gamma appears in the microscopic pressure and does not drop out of the full equations; two separate constants gamma_2, gamma_4 appear in simpler backgrounds. The dilaton-matter coupling beta is a free parameter controlling gravitational screening. No code or numerical experiment is provided.

free parameters (4)
  • gamma = order 1, undetermined
    Introduced in Eq (2.5)/(3.5) as an order-one constant encoding the unknown IFS lifetime tau_IFS ~ 1/g_s and production rate; all microscopic pressures are proportional to it, and it does not drop out of the full equations (3.7).
  • gamma_2 = order 1, undetermined
    Constant in the 1+1d pressure formula (2.5).
  • gamma_4 = order 1, undetermined
    Constant in the 4d pressure formula (2.7).
  • beta = free parameter
    Dilaton coupling to matter mass in Eq (5.8), controls gravitational rescaling G_N -> G_N(1-beta); the paper discusses beta = 0, 1, -4.
assumptions (6)
  • domain assumption IFS pressure in FRW takes the form (3.5), p_IFS = -gamma/(3 g_s^4) (partial phi)^2 Theta(phi-dot), extrapolated from the linear-dilaton result (2.7).
    Sec 3: authors state they lack an exact IFS solution and CFT in FRW and approximate the lifetime as tau_IFS ~ 1/g_s.
  • domain assumption IFS production rate is Gamma = (partial phi)^2 / g_s^2 Theta(phi-dot), local in time.
    Eq (3.4), assumed by analogy with (2.3); no exact CFT in FRW.
  • domain assumption IFSs decay quickly into radiation (gravitons), with the Bianchi identity (3.6) governing rho_IFS.
    Appendix A, equations (A.10).
  • domain assumption The validity condition g_s >> H (3.2) holds, so the IFS lifetime is shorter than the Hubble time.
    Eq (3.3), required for the effective equations.
  • domain assumption Slow-roll conditions (4.1) hold: -V' >> kappa g_s^2 V and -V' >> g_s^2 V''/kappa.
    Sec 4, ensures the attractor (4.2).
  • standard math Standard string-frame action (A.1) and conformal transformation to Einstein frame.
    Appendix A.
invented entities (2)
  • IFS gas (cosmological gas of Instant Folded Strings)
    purpose: Provides negative pressure that drives slow-roll universe and bounces; its backreaction yields effective equations (3.7).
    IFSs were introduced in earlier papers by the same authors; their cosmological gas form (3.5) is assumed here with no independent observational handle. Predicted null modes with E ~ -1/g_s are testable in principle, but not yet observed.
  • Null mode with large negative energy E ~ -1/g_s, P = +/-E
    purpose: Predicted decay channel of IFSs that could imprint on LSS/CMB.
    Discussed in Sec 4.1, Eq (4.10), based on [6]; no detection.

how reviews work

0 comments
Cite this review

Pith. "Pith review of Instant Cosmology." pith.science (2026). https://pith.science/paper/2PRLGLID

@misc{pith2026241202630,
  author       = {Pith},
  title        = {Pith review of: Instant Cosmology},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/2PRLGLID}},
  note         = {Machine review of arXiv:2412.02630}
}
read the original abstract

Instant Folded Strings (IFSs) are unconventional light strings that emerge when the string coupling increases with time. A particularly intriguing property of IFSs, especially relevant to cosmology, is that they violate the Null Energy Condition (NEC). In this paper, we begin to explore their cosmological effects. We find that NEC violation by IFSs is significantly suppressed in an expanding universe, leading to a universe that resembles our own, comprising matter, radiation, and dark energy. Upon closer examination, these components exhibit subtle, nonstandard traits that could be experimentally tested in the future. Notably, the origin of dark energy stems not only from the potential, as is usually the case, but also from the derivative of the potential with respect to the dilaton. This paves the way for a new approach to realizing inflation within string theory, addressing the Dine-Seiberg problem associated with dilaton stabilization, and perhaps even hinting at a novel mechanism to tackle the cosmological constant problem. Conversely, in a contracting universe, the effects of IFSs are amplified, making bouncing cosmologies a natural and prevalent outcome.

Figures

Figures reproduced from arXiv: 2412.02630 by the authors.

Figure 1
Figure 1. The IFS solution. A closed folded string is classically created at a specific moment [PITH_FULL_IMAGE:figures/full_fig_p005_1.png] view at source ↗
Figure 2
Figure 2. The Dine-Seiberg problem and IFSs. The runaway case (a) is not affected by [PITH_FULL_IMAGE:figures/full_fig_p014_2.png] view at source ↗
Figure 3
Figure 3. KKLT and instant cosmology. The blue line represents a typical KKLT potential [PITH_FULL_IMAGE:figures/full_fig_p015_3.png] view at source ↗
Figures from the paper (1 more)
Figure 4
Figure 4. Figure 4: An example for a bouncing solution obtained numerically, initially [PITH_FULL_IMAGE:figures/full_fig_p019_4.png]

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

59 extracted references · 19 canonical work pages

  1. [1]

    Stringy instability inside the black hole,

    N. Itzhaki, “Stringy instability inside the black hole,” JHEP 1810, 145 (2018) doi:10.1007/JHEP10(2018)145 [arXiv:1808.02259 [hep-th]]

    arXiv 2018

  2. [2]

    Is the Superstring Weakly Coupled?,

    M. Dine and N. Seiberg, “Is the Superstring Weakly Coupled?,” Phys. Lett. B 162, 299-302 (1985) doi:10.1016/0370-2693(85)90927-X

    work page doi:10.1016/0370-2693(85)90927-x 1985

  3. [3]

    The Averaged Null Energy Condition and the Black Hole Interior in String Theory,

    K. Attali and N. Itzhaki, “The Averaged Null Energy Condition and the Black Hole Interior in String Theory,” Nucl. Phys. B 943, 114631 (2019) doi:10.1016/j.nuclphysb.2019.114631 [arXiv:1811.12117 [hep-th]]. 28

    work page arXiv 2019

  4. [4]

    A Worldsheet Description of Instant Folded Strings

    A. Hashimoto, N. Itzhaki and U. Peleg, “A Worldsheet Description of Instant Folded Strings,” . J. High Energ. Phys. 2023, 88 (2023). doi:10.1007/JHEP02(2023)088 [arXiv:2209.04988 [hep-th]]

    work page Pith review arXiv 2023

  5. [5]

    String Theory and The Arrow of Time

    N. Itzhaki, “String Theory and The Arrow of Time,” JHEP 03, 192 (2021) doi:10.1007/JHEP03(2021)192 [arXiv:2101.10142 [hep-th]]

    work page Pith review arXiv 2021

  6. [6]

    When Strings Surprise

    N. Itzhaki, U. Peleg, “When strings surprise,”. J. High Energ. Phys. 2024, 172 (2024). https://doi.org/10.1007/JHEP08(2024)172 [arXiv:2404.03215 [hep-th]]

    work page Pith review arXiv 2024

  7. [7]

    Space-Time Supersymmetry in Compactified String Theory and Supercon- formal Models,

    D. Gepner, “Space-Time Supersymmetry in Compactified String Theory and Supercon- formal Models,” Nucl. Phys. B 296, 757 (1988) doi:10.1016/0550-3213(88)90397-5

    doi:10.1016/0550-3213(88)90397-5 1988

  8. [8]

    On the timelike Liouville three-point function,

    G. Giribet, “On the timelike Liouville three-point function,” Phys. Rev. D 85, 086009 (2012) doi:10.1103/PhysRevD.85.086009 [arXiv:1110.6118 [hep-th]]

    arXiv 2012

Show all 59 references
  1. [9]

    Pair Production at Strong Coupling in Weak External Fields,

    I. K. Affleck, O. Alvarez and N. S. Manton, “Pair Production at Strong Coupling in Weak External Fields,” Nucl. Phys. B 197, 509-519 (1982) doi:10.1016/0550-3213(82)90455-2

    1982 doi

  2. [10]

    World-line instantons and the Schwinger effect as a Wentzel–Kramers–Brillouin exact path integral,

    J. Gordon and G. W. Semenoff, “World-line instantons and the Schwinger effect as a Wentzel–Kramers–Brillouin exact path integral,” J. Math. Phys. 56, 022111 (2015) [er- ratum: J. Math. Phys. 59, no.1, 019901 (2018)] doi:10.1063/1.4908556 [arXiv:1407.0987 [hep-th]]

    2015 arXiv

  3. [11]

    Schwinger pair production: Explicit Localization of the world-line instanton,

    J. Gordon and G. W. Semenoff, “Schwinger pair production: Explicit Localization of the world-line instanton,” [arXiv:1612.05909 [hep-th]]

    arXiv

  4. [12]

    Boundary Liouville field theory. 1. Boundary state and boundary two point function,

    V. Fateev, A. B. Zamolodchikov and A. B. Zamolodchikov, “Boundary Liouville field theory. 1. Boundary state and boundary two point function,” [arXiv:hep-th/0001012 [hep-th]]

    arXiv

  5. [13]

    Remarks on Liouville theory with boundary,

    J. Teschner, “Remarks on Liouville theory with boundary,” PoS tmr2000, 041 (2000) doi:10.22323/1.006.0041 [arXiv:hep-th/0009138 [hep-th]]

    2000 arXiv

  6. [14]

    Bouncing Cosmology in 1+1 Dimensions,

    H. A. Meir, “Bouncing Cosmology in 1+1 Dimensions,” [arXiv:2409.09671 [hep-th]]

    arXiv

  7. [15]

    A puncture in the Euclidean black hole,

    R. Brustein, A. Giveon, N. Itzhaki and Y. Zigdon, “A puncture in the Euclidean black hole,” JHEP 04, 021 (2022) doi:10.1007/JHEP04(2022)021 [arXiv:2112.03048 [hep-th]]

    2022 arXiv

  8. [16]

    Private discussion with D. Kutasov

  9. [17]

    A Vestige of FZZ Duality in Higher Dimensions,

    C. Krishnan and S. Talukdar, “A Vestige of FZZ Duality in Higher Dimensions,” [arXiv:2411.16669 [hep-th]]. 29

    arXiv

  10. [18]

    A Semiclassical limit of the gauge / string correspondence,

    S. S. Gubser, I. R. Klebanov and A. M. Polyakov, “A Semiclassical limit of the gauge / string correspondence,” Nucl. Phys. B 636, 99-114 (2002) doi:10.1016/S0550- 3213(02)00373-5 [arXiv:hep-th/0204051 [hep-th]]

    2002 arXiv

  11. [19]

    Strings as soli- tons and black holes as strings,

    A. Dabholkar, J. P. Gauntlett, J. A. Harvey and D. Waldram, “Strings as soli- tons and black holes as strings,” Nucl. Phys. B 474 (1996), 85-121 doi:10.1016/0550- 3213(96)00266-0 [arXiv:hep-th/9511053 [hep-th]]

    1996 arXiv

  12. [20]

    Superstrings and solitons,

    A. Dabholkar, J. P. Gauntlett, J. A. Harvey and F. R. Ruiz, “Superstrings and solitons,” Nucl. Phys. B 340 (1990), doi.org/10.1016/0550-3213(90)90157-9

    1990 doi

  13. [21]

    Cosmology with a Time Variable Cosmological Con- stant,

    P. J. E. Peebles and B. Ratra, “Cosmology with a Time Variable Cosmological Con- stant,” Astrophys. J. Lett. 325, L17 (1988) doi:10.1086/185100

    1988 doi

  14. [22]

    Cosmology and the Fate of Dilatation Symmetry,

    C. Wetterich, “Cosmology and the Fate of Dilatation Symmetry,” Nucl. Phys. B 302, 668-696 (1988) doi:10.1016/0550-3213(88)90193-9 [arXiv:1711.03844 [hep-th]]

    1988 arXiv

  15. [23]

    Cosmological imprint of an energy component with general equation of state,

    R. R. Caldwell, R. Dave and P. J. Steinhardt, “Cosmological imprint of an energy component with general equation of state,” Phys. Rev. Lett. 80, 1582-1585 (1998) doi:10.1103/PhysRevLett.80.1582 [arXiv:astro-ph/9708069 [astro-ph]]

    1998 arXiv

  16. [24]

    The Hubble Tension and Early Dark Energy,

    M. Kamionkowski and A. G. Riess, “The Hubble Tension and Early Dark Energy,” Ann. Rev. Nucl. Part. Sci. 73, 153-180 (2023) doi:10.1146/annurev-nucl-111422-024107 [arXiv:2211.04492 [astro-ph.CO]]

    2023 arXiv

  17. [25]

    A Del- icate universe,

    D. Baumann, A. Dymarsky, I. R. Klebanov, L. McAllister and P. J. Steinhardt, “A Del- icate universe,” Phys. Rev. Lett. 99, 141601 (2007) doi:10.1103/PhysRevLett.99.141601 [arXiv:0705.3837 [hep-th]]

    2007 arXiv

  18. [26]

    Challenges for superstring cosmology,

    R. Brustein and P. J. Steinhardt, “Challenges for superstring cosmology,” Phys. Lett. B 302, 196-201 (1993) doi:10.1016/0370-2693(93)90384-T [arXiv:hep-th/9212049 [hep-th]]

    1993 arXiv

  19. [27]

    Inflection Point Inflation and Time Dependent Po- tentials in String Theory,

    N. Itzhaki and E. D. Kovetz, “Inflection Point Inflation and Time Dependent Po- tentials in String Theory,” JHEP 10, 054 (2007) doi:10.1088/1126-6708/2007/10/054 [arXiv:0708.2798 [hep-th]]

    2007 arXiv

  20. [28]

    Monodromy in the CMB: Gravity Waves and String Inflation,

    E. Silverstein and A. Westphal, “Monodromy in the CMB: Gravity Waves and String Inflation,” Phys. Rev. D 78, 106003 (2008) doi:10.1103/PhysRevD.78.106003 [arXiv:0803.3085 [hep-th]]

    2008 arXiv

  21. [29]

    Initial conditions for inflation,

    D. S. Goldwirth and T. Piran, “Initial conditions for inflation,” Phys. Rept. 214, 223- 291 (1992) doi:10.1016/0370-1573(92)90073-9 30

    1992 doi

  22. [30]

    Inflationary schism,

    A. Ijjas, P. J. Steinhardt and A. Loeb, “Inflationary schism,” Phys. Lett. B736, 142-146 (2014) doi:10.1016/j.physletb.2014.07.012 [arXiv:1402.6980 [astro-ph.CO]]

    2014 arXiv

  23. [31]

    Initial conditions for inflation — A short review,

    R. Brandenberger, “Initial conditions for inflation — A short review,” Int. J. Mod. Phys. D 26, no.01, 1740002 (2016) doi:10.1142/S0218271817400028 [arXiv:1601.01918 [hep-th]]

    2016 arXiv

  24. [32]

    On the problem of initial conditions for inflation,

    A. Linde, “On the problem of initial conditions for inflation,” Found. Phys. 48, no.10, 1246-1260 (2018) doi:10.1007/s10701-018-0177-9 [arXiv:1710.04278 [hep-th]]

    2018

  25. [33]

    Cosmology for Grand Unified Theories with Radiatively Induced Symmetry Breaking,

    A. Albrecht and P. J. Steinhardt, “Cosmology for Grand Unified Theories with Radiatively Induced Symmetry Breaking,” Phys. Rev. Lett. 48, 1220-1223 (1982) doi:10.1103/PhysRevLett.48.1220

    1982 doi

  26. [34]

    The Overshoot Problem and Giant Structures,

    N. Itzhaki, “The Overshoot Problem and Giant Structures,” JHEP 10, 061 (2008) doi:10.1088/1126-6708/2008/10/061 [arXiv:0807.3216 [hep-th]]

    2008 arXiv

  27. [35]

    Cosmological Imprints of Pre-Inflationary Particles,

    A. Fialkov, N. Itzhaki and E. D. Kovetz, “Cosmological Imprints of Pre-Inflationary Particles,” JCAP 02, 004 (2010) doi:10.1088/1475-7516/2010/02/004 [arXiv:0911.2100 [astro-ph.CO]]

    2010 arXiv

  28. [36]

    A model with cosmological Bell inequalities,

    J. Maldacena, “A model with cosmological Bell inequalities,” Fortsch. Phys. 64, 10-23 (2016) doi:10.1002/prop.201500097 [arXiv:1508.01082 [hep-th]]

    2016 arXiv

  29. [37]

    Moduli Stabilization in String Theory,

    L. McAllister and F. Quevedo, “Moduli Stabilization in String Theory,” [arXiv:2310.20559 [hep-th]]

    arXiv

  30. [38]

    De Sitter vacua in string theory,

    S. Kachru, R. Kallosh, A. D. Linde and S. P. Trivedi, “De Sitter vacua in string theory,” Phys. Rev. D 68, 046005 (2003) doi:10.1103/PhysRevD.68.046005 [arXiv:hep-th/0301240 [hep-th]]

    2003 arXiv

  31. [39]

    Supersymmetry Breaking by Fluxes,

    S. Sethi, “Supersymmetry Breaking by Fluxes,” JHEP 10, 022 (2018) doi:10.1007/JHEP10(2018)022 [arXiv:1709.03554 [hep-th]]

    2018 arXiv

  32. [40]

    Uplifting Runaways,

    I. Bena, E. Dudas, M. Gra˜ na and S. L¨ ust, “Uplifting Runaways,” Fortsch. Phys. 67, no.1-2, 1800100 (2019) doi:10.1002/prop.201800100 [arXiv:1809.06861 [hep-th]]

    2019 arXiv

  33. [41]

    Is the horizon of an eternal black hole really smooth?,

    N. Itzhaki, “Is the horizon of an eternal black hole really smooth?,” JHEP 05, 157 (2023) doi:10.1007/JHEP05(2023)157 [arXiv:2302.03556 [hep-th]]

    2023 arXiv

  34. [42]

    The Swampland: Introduction and Review,

    E. Palti, “The Swampland: Introduction and Review,” Fortsch. Phys. 67, no.6, 1900037 (2019) doi:10.1002/prop.201900037 [arXiv:1903.06239 [hep-th]]. 31

    2019 arXiv

  35. [43]

    Lectures on the string landscape and the Swampland,

    N. B. Agmon, A. Bedroya, M. J. Kang and C. Vafa, “Lectures on the string landscape and the Swampland,” [arXiv:2212.06187 [hep-th]]

    arXiv

  36. [44]

    The Hierarchy problem and new dimensions at a millimeter,

    N. Arkani-Hamed, S. Dimopoulos and G. R. Dvali, “The Hierarchy problem and new dimensions at a millimeter,” Phys. Lett. B 429, 263-272 (1998) doi:10.1016/S0370- 2693(98)00466-3 [arXiv:hep-ph/9803315 [hep-ph]]

    1998 arXiv

  37. [45]

    New dimensions at a millimeter to a Fermi and superstrings at a TeV,

    I. Antoniadis, N. Arkani-Hamed, S. Dimopoulos and G. R. Dvali, “New dimensions at a millimeter to a Fermi and superstrings at a TeV,” Phys. Lett. B 436, 257-263 (1998) doi:10.1016/S0370-2693(98)00860-0 [arXiv:hep-ph/9804398 [hep-ph]]

    1998 arXiv

  38. [46]

    A Large mass hierarchy from a small extra dimension,

    L. Randall and R. Sundrum, “A Large mass hierarchy from a small extra dimension,” Phys. Rev. Lett. 83, 3370-3373 (1999) doi:10.1103/PhysRevLett.83.3370 [arXiv:hep- ph/9905221 [hep-ph]]

    1999

  39. [47]

    An Alternative to compactification,

    L. Randall and R. Sundrum, “An Alternative to compactification,” Phys. Rev. Lett. 83, 4690-4693 (1999) doi:10.1103/PhysRevLett.83.4690 [arXiv:hep-th/9906064 [hep-th]]

    1999 arXiv

  40. [48]

    Supersymmetric gauge theories,

    D. S. Berman and E. Rabinovici, “Supersymmetric gauge theories,” [arXiv:hep- th/0210044 [hep-th]]

  41. [49]

    Invariance under complex transformations, and its relevance to the cosmological constant problem,

    G. ’t Hooft and S. Nobbenhuis, “Invariance under complex transformations, and its relevance to the cosmological constant problem,” Class. Quant. Grav. 23, 3819-3832 (2006) doi:10.1088/0264-9381/23/11/009 [arXiv:gr-qc/0602076 [gr-qc]]

    2006 arXiv

  42. [50]

    Scale factor duality for classical and quantum strings,

    G. Veneziano, “Scale factor duality for classical and quantum strings,” Phys. Lett. B 265, 287-294 (1991) doi:10.1016/0370-2693(91)90055-U

    1991 doi

  43. [51]

    The Graceful exit problem in string cosmology,

    R. Brustein and G. Veneziano, “The Graceful exit problem in string cosmology,” Phys. Lett. B 329, 429-434 (1994) doi:10.1016/0370-2693(94)91086-3 [arXiv:hep-th/9403060 [hep-th]]

    1994 arXiv

  44. [52]

    Towards a singularity - free inflation- ary universe?,

    N. Kaloper, R. Madden and K. A. Olive, “Towards a singularity - free inflation- ary universe?,” Nucl. Phys. B 452, 677-704 (1995) doi:10.1016/0550-3213(95)00398-C [arXiv:hep-th/9506027 [hep-th]]

    1995 arXiv

  45. [53]

    Tree level string cosmology,

    R. Easther, K. i. Maeda and D. Wands, “Tree level string cosmology,” Phys. Rev. D 53, 4247-4256 (1996) doi:10.1103/PhysRevD.53.4247 [arXiv:hep-th/9509074 [hep-th]]

    1996 arXiv

  46. [54]

    The Ekpyrotic universe: Colliding branes and the origin of the hot big bang,

    J. Khoury, B. A. Ovrut, P. J. Steinhardt and N. Turok, “The Ekpyrotic universe: Colliding branes and the origin of the hot big bang,” Phys. Rev. D 64, 123522 (2001) doi:10.1103/PhysRevD.64.123522 [arXiv:hep-th/0103239 [hep-th]]. 32

    2001 arXiv

  47. [55]

    From big crunch to big bang,

    J. Khoury, B. A. Ovrut, N. Seiberg, P. J. Steinhardt and N. Turok, “From big crunch to big bang,” Phys. Rev. D 65, 086007 (2002) doi:10.1103/PhysRevD.65.086007 [arXiv:hep- th/0108187 [hep-th]]

    2002

  48. [56]

    From big bang to big crunch and beyond,

    S. Elitzur, A. Giveon, D. Kutasov and E. Rabinovici, “From big bang to big crunch and beyond,” JHEP 06, 017 (2002) doi:10.1088/1126-6708/2002/06/017 [arXiv:hep- th/0204189 [hep-th]]

    2002

  49. [57]

    Bouncing Cosmologies: Progress and Problems,

    R. Brandenberger and P. Peter, “Bouncing Cosmologies: Progress and Problems,” Found. Phys. 47, no.6, 797-850 (2017) doi:10.1007/s10701-016-0057-0 [arXiv:1603.05834 [hep-th]]

    2017 arXiv

  50. [58]

    Nonsingular Ekpyrotic Cosmology with a Nearly Scale- Invariant Spectrum of Cosmological Perturbations and Gravitational Waves,

    R. Brandenberger and Z. Wang, “Nonsingular Ekpyrotic Cosmology with a Nearly Scale- Invariant Spectrum of Cosmological Perturbations and Gravitational Waves,” Phys. Rev. D 101, no.6, 063522 (2020) doi:10.1103/PhysRevD.101.063522 [arXiv:2001.00638 [hep- th]]

    2020 arXiv

  51. [59]

    Smoothing and flatten- ing the universe through slow contraction versus inflation,

    A. Ijjas, P. J. Steinhardt, D. Garfinkle and W. G. Cook, “Smoothing and flatten- ing the universe through slow contraction versus inflation,” JCAP 07, 077 (2024) doi:10.1088/1475-7516/2024/07/077 [arXiv:2404.00867 [gr-qc]]. 33

    2024 arXiv

Pith tools

Reviewed August 11, 2026 · model on record in the stance chip above.