Classical Solutions in Two-Dimensional String Theory and Gravitational Collapse

A general solution to the $D=2$ 1-loop beta functions equations including tachyonic back reaction on the metric is presented. Dynamical black hole (classical) solutions representing gravitational collapse of tachyons are constructed. A discussion on the correspondence with the matrix-model approach is given.Comment: 7 pages, UTTG-31-9

General Omega Deformations from Closed String Backgrounds

In this note, an important extension to the recent construction of the fluxtrap background is presented. The fluxtrap is a closed string background based on the Melvin solution corresponding to the Omega deformation of flat space. In this note, we introduce the mechanisms to extend it from epsilon_1=-epsilon_2 in R to more general values of epsilon_1 and epsilon_2 in C.Comment: 12 pages. Typos corrected, some clarifications in text. Version accepted for publication in JHE

The Omega Deformation From String and M-Theory

We present a string theory construction of Omega-deformed four-dimensional gauge theories with generic values of \epsilon_1 and \epsilon_2. Our solution gives an explicit description of the geometry in the core of Nekrasov and Witten's realization of the instanton partition function, far from the asymptotic region of their background. This construction lifts naturally to M-theory and corresponds to an M5-brane wrapped on a Riemann surface with a selfdual flux. Via a 9-11 flip, we finally reinterpret the Omega deformation in terms of non-commutative geometry. Our solution generates all modified couplings of the \Omega-deformed gauge theory, and also yields a geometric origin for the quantum spectral curve of the associated quantum integrable system.Comment: LaTeX, 35 pages, 1 figure. Appendix on couplings of hypermultiplets in N=4 SYM adde

Blocking Zika virus vertical transmission.

The outbreak of the Zika virus (ZIKV) has been associated with increased incidence of congenital malformations. Although recent efforts have focused on vaccine development, treatments for infected individuals are needed urgently. Sofosbuvir (SOF), an FDA-approved nucleotide analog inhibitor of the Hepatitis C (HCV) RNA-dependent RNA polymerase (RdRp) was recently shown to be protective against ZIKV both in vitro and in vivo. Here, we show that SOF protected human neural progenitor cells (NPC) and 3D neurospheres from ZIKV infection-mediated cell death and importantly restored the antiviral immune response in NPCs. In vivo, SOF treatment post-infection (p.i.) decreased viral burden in an immunodeficient mouse model. Finally, we show for the first time that acute SOF treatment of pregnant dams p.i. was well-tolerated and prevented vertical transmission of the virus to the fetus. Taken together, our data confirmed SOF-mediated sparing of human neural cell types from ZIKV-mediated cell death in vitro and reduced viral burden in vivo in animal models of chronic infection and vertical transmission, strengthening the growing body of evidence for SOF anti-ZIKV activity

Avoiding catastrophic failure in correlated networks of networks

Networks in nature do not act in isolation but instead exchange information, and depend on each other to function properly. An incipient theory of Networks of Networks have shown that connected random networks may very easily result in abrupt failures. This theoretical finding bares an intrinsic paradox: If natural systems organize in interconnected networks, how can they be so stable? Here we provide a solution to this conundrum, showing that the stability of a system of networks relies on the relation between the internal structure of a network and its pattern of connections to other networks. Specifically, we demonstrate that if network inter-connections are provided by hubs of the network and if there is a moderate degree of convergence of inter-network connection the systems of network are stable and robust to failure. We test this theoretical prediction in two independent experiments of functional brain networks (in task- and resting states) which show that brain networks are connected with a topology that maximizes stability according to the theory.Comment: 40 pages, 7 figure

Quantum Cosmology of Generalized Two--Dimensional Dilaton Gravity Models

The quantum cosmology of two-dimensional dilaton-gravity models is investigated. A class of models is mapped onto the constrained oscillator-ghost-oscillator model. A number of exact and approximate solutions to the corresponding Wheeler-DeWitt equation are presented. A wider class of minisuperspace models that can be solved in this fashion is identified. Supersymmetric extensions to the induced gravity theory and the bosonic string theory are then considered and closed-form solutions to the associated quantum constraints are derived. The possibility of applying the third-quantization procedure to two-dimensional dilaton-gravity is briefly discussed.Comment: 28 pages, late

The Frequency Following Response (FFR) May Reflect Pitch-Bearing Information But is Not a Direct Representation of Pitch

The frequency following response (FFR), a scalp-recorded measure of phase-locked brainstem activity, is often assumed to reflect the pitch of sounds as perceived by humans. In two experiments, we investigated the characteristics of the FFR evoked by complex tones. FFR waveforms to alternating-polarity stimuli were averaged for each polarity and added, to enhance envelope, or subtracted, to enhance temporal fine structure information. In experiment 1, frequency-shifted complex tones, with all harmonics shifted by the same amount in Hertz, were presented diotically. Only the autocorrelation functions (ACFs) of the subtraction-FFR waveforms showed a peak at a delay shifted in the direction of the expected pitch shifts. This expected pitch shift was also present in the ACFs of the output of an auditory nerve model. In experiment 2, the components of a harmonic complex with harmonic numbers 2, 3, and 4 were presented either to the same ear (“mono”) or the third harmonic was presented contralaterally to the ear receiving the even harmonics (“dichotic”). In the latter case, a pitch corresponding to the missing fundamental was still perceived. Monaural control conditions presenting only the even harmonics (“2 + 4”) or only the third harmonic (“3”) were also tested. Both the subtraction and the addition waveforms showed that (1) the FFR magnitude spectra for “dichotic” were similar to the sum of the spectra for the two monaural control conditions and lacked peaks at the fundamental frequency and other distortion products visible for “mono” and (2) ACFs for “dichotic” were similar to those for “2 + 4” and dissimilar to those for “mono.” The results indicate that the neural responses reflected in the FFR preserve monaural temporal information that may be important for pitch, but provide no evidence for any additional processing over and above that already present in the auditory periphery, and do not directly represent the pitch of dichotic stimuli

Author Correction: Blocking Zika virus vertical transmission.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper

String theory of the Omega deformation

In this article, we construct a supersymmetric real mass deformation for the adjoint chiral multiplets in the gauge theory describing the dynamics of a stack of D2-branes in type II string theory. We do so by placing the D2-branes into the T-dual of a supersymmetric NS fluxbrane background. We furthermore note that this background is the string theoretic realization of an Omega-deformation of flat space in the directions transverse to the branes where the deformation parameters satisfy \epsilon_1 = - \epsilon_2. This \Omega-deformation therefore serves to give supersymmetric real masses to the chiral multiplets of the 3D gauge theory. To illustrate the physical effect of the real mass term, we derive BPS-saturated classical solutions for the branes rotating in this background. Finally, we reproduce all the same structure in the presence of NS fivebranes and comment on the relationship to the gauge theory/spin-chain correspondence of Nekrasov and Shatashvili.Comment: 36 pages. References added, brane construction clarified, edited for styl