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A String-Inspired Model for the Low-$\ell$ CMB
High Energy Physics - Theory · Submitted 15 Mar 2015
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim For the first 32 multipoles, combining the hard exponential with a milder one leading to $n_s\simeq 0.96$ and with a small gaussian bump we have attained a reduction of $\chi^{\,2}$ to about 46% of the standard $\Lambda$CDM setting, with both WMAP9 and PLANCK 2013 data.
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The abstract, sentence by sentence
We present a semi--analytic exploration of some low--$\ell$ angular power spectra inspired by "Brane Supersymmetry Breaking". This mechanism splits Bose and Fermi excitations in String Theory, leaving behind an exponential potential that is just too steep for the inflaton to emerge from the initial singularity while descending it. As a result, the scalar generically bounces against the exponential wall, which typically introduces an infrared depression and a pre--inflationary peak in the power spectrum of scalar perturbations. We elaborate on a possible link between this phenomenon and the low--$\ell$ CMB. For the first 32 multipoles, combining the hard exponential with a milder one leading to $n_s\simeq 0.96$ and with a small gaussian bump we have attained a reduction of $\chi^{\,2}$ to about 46% of the standard $\Lambda$CDM setting, with both WMAP9 and PLANCK 2013 data. This result corresponds to a $\chi^{\,2}/DOF$ of about 0.45, to be compared with a $\Lambda$CDM value of about 0.85. The preferred choices combine naturally quadrupole depression, a first peak around $\ell=5$ and a wide minimum around $\ell=20$. We have also gathered some evidence that similar spectra emerge if the hard exponential is combined with more realistic models of inflation. A problem of the preferred examples is their slow convergence to an almost scale--invariant profile.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We present a semi--analytic exploration of some low--$\ell$ angular power spectra inspired by "Brane Supersymmetry Breaking". | contribution 1.00 | 0.93 | 0.06 | asserted 0.98 |
| s1 | This mechanism splits Bose and Fermi excitations in String Theory, leaving behind an exponential potential that is just too steep for the inflaton to emerge from the initial singularity while descending it. | background 0.88 | 0.10 | 0.05 | asserted 1.00 |
| s2 | As a result, the scalar generically bounces against the exponential wall, which typically introduces an infrared depression and a pre--inflationary peak in the power spectrum of scalar perturbations. | result 0.72 | 0.36 | 0.13 | asserted 0.59 |
| s3 | We elaborate on a possible link between this phenomenon and the low--$\ell$ CMB. | interpretation 0.56 | 0.59 | 0.11 | hedged possibility 0.93 |
| s4 | For the first 32 multipoles, combining the hard exponential with a milder one leading to $n_s\simeq 0.96$ and with a small gaussian bump we have attained a reduction of $\chi^{\,2}$ to about 46% of the standard $\Lambda$CDM setting, with both WMAP9 and PLANCK 2013 data. | result 0.99 | 0.96 | 0.55 | asserted 1.00 |
| s5 | This result corresponds to a $\chi^{\,2}/DOF$ of about 0.45, to be compared with a $\Lambda$CDM value of about 0.85. | result 0.99 | 0.90 | 0.18 | asserted 0.99 |
| s6 | The preferred choices combine naturally quadrupole depression, a first peak around $\ell=5$ and a wide minimum around $\ell=20$. | result 0.91 | 0.87 | 0.17 | asserted 0.98 |
| s7 | We have also gathered some evidence that similar spectra emerge if the hard exponential is combined with more realistic models of inflation. | result 0.93 | 0.87 | 0.07 | hedged possibility 0.72 |
| s8 | A problem of the preferred examples is their slow convergence to an almost scale--invariant profile. | limitation 1.00 | 0.77 | 0.04 | asserted 1.00 |
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The paper
Original abstract
We present a semi--analytic exploration of some low--$\ell$ angular power spectra inspired by "Brane Supersymmetry Breaking". This mechanism splits Bose and Fermi excitations in String Theory, leaving behind an exponential potential that is just too steep for the inflaton to emerge from the initial singularity while descending it. As a result, the scalar generically bounces against the exponential wall, which typically introduces an infrared depression and a pre--inflationary peak in the power spectrum of scalar perturbations. We elaborate on a possible link between this phenomenon and the low--$\ell$ CMB. For the first 32 multipoles, combining the hard exponential with a milder one leading to $n_s\simeq 0.96$ and with a small gaussian bump we have attained a reduction of $\chi^{\,2}$ to about 46% of the standard $\Lambda$CDM setting, with both WMAP9 and PLANCK 2013 data. This result corresponds to a $\chi^{\,2}/DOF$ of about 0.45, to be compared with a $\Lambda$CDM value of about 0.85. The preferred choices combine naturally quadrupole depression, a first peak around $\ell=5$ and a wide minimum around $\ell=20$. We have also gathered some evidence that similar spectra emerge if the hard exponential is combined with more realistic models of inflation. A problem of the preferred examples is their slow convergence to an almost scale--invariant profile.
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References
How the literature uses it
7 arXiv papers cite this in 7 sentences
Papers citing it · 2 sentences without a confident label
Cites it as background 5 papers
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Lack of power at low CMB multipoles can be attributed to spatial curvature [ref] , non-trivial topology [ref] , violation of statistical anisotropies [ref] , hemispherical anisotropy and non-gaussianity [ref] , bouncing inflation [ref] , dark energy during the inflation [ref] , primordial micro black holes [ref] , loop quantum cosmology [ref] , string theory [ref] , non-attractor initial conditions [ref] and so on.
Low-$\ell$ power suppression in punctuated inflation · Introduction · 0.90
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Some supersymmetry-breaking mechanisms appear to yield naturally other types of cosmologies [ref] , whose implications for Cosmic Microwave Background anomalies have been explored in [ref] , while the associated instabilities suggest the possibility of dS braneworlds [ref] .
String Tension between de Sitter vacua and Curvature Corrections · Introduction · 0.86
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For example, many scenarios involving other kinds of modifications of the cosmological history prior to inflation — among them fast-roll inflation , inflection-point inflation [ref] , “climbing-scalar” scenarios in braneworld cosmologies [ref] , other inflationary scenarios in string theory [ref] , and scenarios involving an early epoch of radiation-domination prior to inflation — have been invoked as explanations for the suppression of power at low multipole number in the CMB.
Enlarging the Space of Viable Inflation Models: A Slingshot Mechanism · Conclusions and discussion · 0.93
What it cites · 59 sentences without a confident label
Builds on 2 papers
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The present work is meant to complement the analysis in [ref] with a scrutiny of new effects introduced by the gaussian bump.
Pre - Inflationary Clues from String Theory ? · Introduction · 0.95
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The present work is meant to complement the analysis in [ref] with a scrutiny of new effects introduced by the gaussian bump.
String Theory clues for the low-$\ell$ CMB ? · Introduction · 0.95
Uses data or values from 5 papers
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The temperature anisotropies observed by WMAP [ref] and PLANCK [ref] - [ref] are confronting us with inflaton scalar perturbations consistent with primordial power spectra that are almost scale invariant over about three orders of magnitude, with $P(k) ∼k^ n_s-1$ and $n_s ≃0.96$.
Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Final Maps and Results · Introduction · 0.92
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The temperature anisotropies observed by WMAP [ref] and PLANCK [ref] - [ref] are confronting us with inflaton scalar perturbations consistent with primordial power spectra that are almost scale invariant over about three orders of magnitude, with $P(k) ∼k^ n_s-1$ and $n_s ≃0.96$.
Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Parameter Results · Introduction · 0.92
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The temperature anisotropies observed by WMAP [ref] and PLANCK [ref] - [ref] are confronting us with inflaton scalar perturbations consistent with primordial power spectra that are almost scale invariant over about three orders of magnitude, with $P(k) ∼k^ n_s-1$ and $n_s ≃0.96$.
Planck 2013 results. I. Overview of products and scientific results · Introduction · 0.92
Compares with 3 papers
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The end result is similar to what occurred close to the exponential wall in [ref] and in [ref] .
CMB Imprints of a Pre-Inflationary Climbing Phase · Comparison with the low–$ℓ$ CMB · 0.97
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The end result is similar to what occurred close to the exponential wall in [ref] and in [ref] .
Pre - Inflationary Clues from String Theory ? · Comparison with the low–$ℓ$ CMB · 0.97
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The end result is similar to what occurred close to the exponential wall in [ref] and in [ref] .
String Theory clues for the low-$\ell$ CMB ? · Comparison with the low–$ℓ$ CMB · 0.97
Cites as background 4 papers
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This phenomenon occurs in classically stable vacua of String Theory [ref] - [ref] (for reviews see [ref] ) where branes and orientifolds are individually BPS and yet are collectively incompatible with Supersymmetry.
Theory and Phenomenology of Type I strings and M-theory · Introduction · 0.84
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This phenomenon occurs in classically stable vacua of String Theory [ref] - [ref] (for reviews see [ref] ) where branes and orientifolds are individually BPS and yet are collectively incompatible with Supersymmetry.
Open Strings · Introduction · 0.84
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This phenomenon occurs in classically stable vacua of String Theory [ref] - [ref] (for reviews see [ref] ) where branes and orientifolds are individually BPS and yet are collectively incompatible with Supersymmetry.
Open strings and their symmetry groups · Introduction · 0.84
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