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AdS/BCFT from conformal bootstrap: construction of gravity with branes and particles
No full textWe initiate a conformal bootstrap program to study AdS₃/BCFT₂ with heavy excitations. We start by solving the bootstrap equations associated with two-point functions of scalar/non-scalar primaries under the assumption that one-point functions vanish. These correspond to gravity with a brane and a non-spinning/spinning particle where the brane and the particle do not intersect with each other. From the bootstrap equations, we obtain the energy spectrum and the modified black hole threshold. We then carefully analyze the gravity duals and find the results perfectly match the BCFT analysis. In particular, brane self-intersections, which are usually considered to be problematic, are nicely avoided by the black hole formation. Despite the assumption to solve the bootstrap equations, one-point functions of scalar primaries can be non-zero in general. We construct the holographic dual for a non-vanishing one-point function, in which the heavy particle can end on the brane, by holographically computing the Rényi entropy in AdS/BCFT. As a bonus, we find a refined formula for the holographic Rényi entropy, which appears to be crucial to correctly reproduce the boundary entropy term. On the other hand, we explain why one-point functions of non-scalar primaries always vanish from the gravity dual. The non-sensitivity of the solution for the bootstrap equation to the boundary entropy helps us to construct gravity duals with negative tension branes. We also find a holographic dual of boundary primaries
Prototropically Controlled Dynamics of Cytosine Photodecay
No full textThe effect of the existence of several prototropic tautomers of cytosine on its UV/vis spectra and the excited state decay dynamics is studied by spectral and nonadiabatic molecular dynamics (NAMD) simulations in connection with the mixed-reference spin-flip time-dependent density functional theory (MRSF-TDDFT) method. Simulated UV/vis spectra provide a strong indication that the H₃N keto–amino cytosine tautomer (the least anticipated species) may be present under experimental conditions. The NAMD simulations yield a wide range of excited state decay constants for various tautomers of cytosine, ranging from ∼1.3 ps for the biologically relevant H1N keto–amino tautomer to ∼0.1 ps for the keto–imino tautomer. The slowness of the H1N decay dynamics follows from the presence of a barrier on the excited state energy surface separating the Franck–Condon structure from the major decay funnel, the conical intersection seam. It is suggested that the experimentally observed photodecay dynamics may result from a combination of the decay processes of various tautomers (H₃N in particular) present simultaneously under the experimental conditions
Testing relativistic accretion disk models with GRO J1655-40
No full textBlack hole X-ray binaries are ideal environments to test the accretion phenomena in the presence of strong gravitational potentials. KERRBB held an important place in the X-ray spectral continuum method for measuring the black hole spin modeling the emission from the innermost regions of the accretion disk. In this work, we present the results of X-ray spectral analysis using publicly available RXTE data of GRO J1655-40 obtained during the 2005 outburst with the two relativistic accretion disk models, KERRBB and KYNBB. Our analysis showed that both models provide identical results with black hole spin measurements, disk temperature, and disk luminosity when the inner edge of the accretion disk is set at the innermost stable circular orbit (ISCO) for the same accretion rates. We could not obtain reasonable fits for ∼89% of the observations with a fixed black hole spin value at a_* = 0.7 using both models. Allowing the spin parameter to vary improved the fit statistic significantly with reduced χ² values being reduced from ∼10 to 100 to below 2. Both models revealed black hole spin values varying between 0.52 < a_* < 0.94, which can be interpreted as a variable inner edge of the disk throughout different accretion states
Long-lived Andreev states as evidence for protected hinge modes in a bismuth nanoring Josephson junction
No full textSecond-order topological insulators are characterized by helical, non-spin-degenerate one-dimensional states running along opposite crystal hinges with no backscattering. Injecting superconducting pairs therefore entails splitting Cooper pairs into two families of helical Andreev states of opposite helicity, one at each hinge. Here we provide evidence for such separation via the measurement and analysis of the switching supercurrent statistics of a crystalline nanoring of bismuth. Using a phenomenological model of two helical Andreev hinge modes, we find that pairs relax at a rate comparable to individual quasiparticles, in contrast to the much faster pair relaxation of non-topological systems. This constitutes a unique telltale sign of the spatial separation of topological helical hinges
Three Ultra-short-period Contact Eclipsing Binary Systems Mined from Massive Astronomical Surveys
No full textWe present the photometric analysis of three ultra-short-period total eclipsing binaries in contact configuration, CRTS_J172718.0+431624, OGLE-BLG-ECL-000104, and OGLE-BLG-ECL-000012, mined from massive astronomical surveys. Using the available archival light curves (LCs) from Vista Variables in the Vía Láctea (VVV), Optical Gravitational Lensing Experiment (OGLE), Zwicky Transient Facility, and Catalina Sky Survey in different passbands and new multiband photometric observations with the 2.3 m Aristarchos telescope at Helmos Observatory, their relative physical parameters were derived. We explored the parameter space by using the PIKAIA genetic algorithm optimizer. The best photometric solution and error budget estimation were adopted for each system through Markov Chain Monte Carlo sampling of the global optimum. The approximate absolute parameters were derived for each contact system adopting an empirical mass–luminosity relation. All three systems have a mass ratio lower than 0.5. The exchange between the primary and secondary depths of CRTS_J172718.0+431624 during 2016–2022 may be due to spot activity. In addition, we present a detailed analysis of the first well-characterized shortest-period contact eclipsing binary with total eclipses known so far (OGLE-BLG-ECL-000104). Thanks to VVV and OGLE LCs, new distances were derived for OGLE-BLG-ECL-000104 and OGLE-BLG-ECL-000012 using empirical period–luminosity relations. The origin and evolutionary status of all three ultra-short-period contact binaries are thoroughly discussed in the context of the detached binary formation channel
Global receptivity analysis: physically realizable input-output analysis
No full textIn the context of transition analysis, linear input–output analysis determines the worst-case disturbances to a laminar base flow based on a generic right-hand-side volumetric/boundary forcing term. The worst-case forcing is not physically realizable, and, to our knowledge, a generic framework for posing physically realizable worst-case disturbance problems is lacking. In natural receptivity analysis, disturbances are forced by matching (typically local) solutions within the boundary layer to outer solutions consisting of free-stream vortical, entropic and acoustic disturbances. We pose a scattering formalism to restrict the input forcing to a set of realizable disturbances associated with plane-wave solutions of the outer problem. The formulation is validated by comparing with direct numerical simulations of a Mach 4.5 flat-plate boundary layer. We show that the method provides insight into transition mechanisms by identifying those linear combinations of plane-wave disturbances that maximize energy amplification over a range of frequencies. We also discuss how the framework can be extended to accommodate scattering from shocks and in shock layers for supersonic flow
Low energy fold paths in multistable origami structures
No full textOrigami design concepts are finding pervasive utility in engineering applications due to their ability to map complex shape transformations into a series of folding actions. The interplay between stretching, folding, and facet bending modes in origami structures also generates a complex energy landscape of multistable states to leverage for engineering applications. However, identifying rigid and deformable folding paths in this high-dimensional and non-convex energy landscape remains a challenge. To help address this challenge, we first introduce a global, constraint-based approach to modeling origami that uses a redundant kinematic description of the facets and nodes, and treats the kinematic compatibility between these redundant descriptors as a constraint. This approach allows for complex facet shapes without increasing the dimensionality of the system, as would be necessary in truss-based and other node-based formulations in order to stiffen the facet. Secondly, we adopt the nudged elastic band method, that is widely used in computational chemistry, to identify minimum energy folding paths. This strategy addresses, from a global perspective, the difficulty of piecing together sequences of local folding steps in order to connect two different points in configuration space. We implement this path finding approach on both the kinematic constraint formulation and a truss-based model, and compare their behaviors on a series of folding and multistable origami examples
A refined continuity correction for the negative binomial distribution and asymptotics of the median
No full textIn this paper, we prove a local limit theorem and a refined continuity correction for the negative binomial distribution. We present two applications of the results. First, we find the asymptotics of the median for a NegativeBinomial(r,p) random variable jittered by a Uniform(0,1), which answers a problem left open in Coeurjolly and Trépanier (Metrika 83(7):837–851, 2020). This is used to construct a simple, robust and consistent estimator of the parameter p, when r > 0 is known. The case where r is unknown is also briefly covered. Second, we find an upper bound on the Le Cam distance between negative binomial and normal experiments
Competing constraints shape the nonequilibrium limits of cellular decision-making
No full textGene regulation is central to cellular function. Yet, despite decades of work, we lack quantitative models that can predict how transcriptional control emerges from molecular interactions at the gene locus. Thermodynamic models of transcription, which assume that gene circuits operate at equilibrium, have previously been employed with considerable success in the context of bacterial systems. However, the presence of ATP-dependent processes within the eukaryotic transcriptional cycle suggests that equilibrium models may be insufficient to capture how eukaryotic gene circuits sense and respond to input transcription factor concentrations. Here, we employ simple kinetic models of transcription to investigate how energy dissipation within the transcriptional cycle impacts the rate at which genes transmit information and drive cellular decisions. We find that biologically plausible levels of energy input can lead to significant gains in how rapidly gene loci transmit information but discover that the regulatory mechanisms underlying these gains change depending on the level of interference from noncognate activator binding. When interference is low, information is maximized by harnessing energy to push the sensitivity of the transcriptional response to input transcription factors beyond its equilibrium limits. Conversely, when interference is high, conditions favor genes that harness energy to increase transcriptional specificity by proofreading activator identity. Our analysis further reveals that equilibrium gene regulatory mechanisms break down as transcriptional interference increases, suggesting that energy dissipation may be indispensable in systems where noncognate factor interference is sufficiently large
Real-time observation of optical rogue waves in spatiotemporally mode-locked fiber lasers
No full textFiber lasers offer tabletop nonlinear environments to mimic and study the complex dynamics of nature. Optical rogue waves, rarely occurring extreme intensity fluctuations, are one of the many subjects that can be investigated with a fiber laser cavity. Although oceanic rogue waves are a result of spatiotemporal dynamics, the single-mode nature of the fiber laser and the commonly used measurement techniques limit the optical rogue wave studies to only temporal dynamics. In this study, we overcome such limit to observe rogue wave real-time dynamics in spatiotemporally mode-locked fiber lasers by utilizing state-of-the-art compressed ultrafast photography technique. The multimode laser cavity exhibits long-tailed non-Gaussian distributions under relaxed cavity constraints. Single-shot spatiotemporal measurements of rogue events showed that, instead of noise bursts, the cavity produces clean pulses with high-quality beam profiles. Our results indicate that rogue events in spatiotemporally mode-locked fiber lasers undergo nonlinear spatial transformation due to a power-dependent consistent attractor