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View article: Multimodal fNIRS–EEG sensor fusion: Review of data-driven methods and perspective for naturalistic brain imaging
Multimodal fNIRS–EEG sensor fusion: Review of data-driven methods and perspective for naturalistic brain imaging Open
Functional near-infrared spectroscopy (fNIRS), high-density diffuse optical tomography (HD-DOT), and electroencephalography (EEG) are established, cost-effective, and non-invasive neuroimaging techniques, whose integration represents a pro…
View article: On black hole singularity resolution in $D=2$ via duality-invariant $α'$ corrections
On black hole singularity resolution in $D=2$ via duality-invariant $α'$ corrections Open
Starting with the two-derivative limit of $D=2$ string theory, we explore the space of T-duality invariant $α'$ corrections, a space that contains a point representing the fully $α'$-corrected classical string theory. Using a parametrizati…
View article: 2D Black Holes, Bianchi I Cosmologies, and $α'$
2D Black Holes, Bianchi I Cosmologies, and $α'$ Open
We report two surprising results on $α'$ corrections in string theory restricted to massless fields. First, for critical dimension Bianchi type I cosmologies with $q$ scale factors only $q-1$ of them have non-trivial $α'$ corrections. In p…
View article: An $α'$-complete theory of cosmology and its tensionless limit
An $α'$-complete theory of cosmology and its tensionless limit Open
We explore the exactly duality invariant higher-derivative extension of double field theory due to Hohm, Siegel and Zwiebach (HSZ) specialized to cosmological backgrounds. Despite featuring a finite number of derivatives in its original fo…
View article: Duality invariant string beta functions at two loops
Duality invariant string beta functions at two loops Open
A bstract We compute, for cosmological backgrounds, the O ( d, d ; ℝ) invariant beta functions for the sigma model of the bosonic string at two loops. This yields an independent first-principle derivation of the order α ′ corrections to th…
View article: General String Cosmologies at Order $\alpha'{}^{\,3}$
General String Cosmologies at Order $\alpha'{}^{\,3}$ Open
We compute the cosmological reduction of general string theories, including bosonic, heterotic and type II string theory to order $\alpha'^{3}$, i.e., with up to eight derivatives. To this end we refine recently introduced methods that all…
View article: A Puzzle Concerning String Dualities at Order $\alpha'^{\,3}$
A Puzzle Concerning String Dualities at Order $\alpha'^{\,3}$ Open
We show that the cosmological reduction of the fourth powers of the Riemann tensor claimed to arise in string theory at order $\alpha'^{\,3}$, with overall coefficient proportional to $\zeta(3)$, is not invariant under standard $O(9,9)$ tr…