Probe Limit Research Articles

Pole-skipping and chaos in D3-D7 brane systems

In this paper, we analyze the pole-skipping phenomena of finite temperature Yang-Mills theory with quark flavors, which is dual to D3-D7 brane systems in bulk. We also consider the external electric field in the boundary field theory, which is dual to the world volume electric field on the D7 brane. We will work in the probe limit where the D7 branes do not backreact to the D3 brane background. In this scenario, we decode the characteristic parameters of the chaos, namely, Lyapunov exponent λL and butterfly velocity vb from the pole-skipping points by performing the near effective horizon analysis of the linearized Einstein equations. Unlike pure Yang-Mills, once charged quarks with a background electric field are added into the system, the characteristic parameters of the chaos show nontrivial dependence on the quark mass and external electric field. We have observed that λL and vb decreases with increasing electric field. We further perform the pole-skipping analysis for the gauge invariant sound, shear, and tensor modes of the perturbation in the bulk and discuss their physical importance in the holographic context. Published by the American Physical Society 2024

Post-Minkowskian theory meets the spinning effective-one-body approach for two-body scattering

Effective-one-body (EOB) waveforms employed by the LIGO-Virgo-KAGRA Collaboration have primarily been developed by resumming the post-Newtonian expansion of the relativistic two-body problem. Given the recent significant advancements in post-Minkowskian (PM) theory and gravitational self-force formalism, there is considerable interest in creating waveform models that integrate information from various perturbative methods in innovative ways. This becomes particularly crucial when tackling the accuracy challenge posed by upcoming ground-based detectors (such as the Einstein Telescope and Cosmic Explorer) and space-based detectors (such as LISA, TianQin, or Taiji) expected to operate in the next decade. In this context, we present the derivation of the first spinning EOB (SEOB) Hamiltonian that incorporates PM results up to three-loop order: the SEOB-PM model. The model accounts for the complete hyperbolic motion, encompassing nonlocal-in-time tails. To evaluate its accuracy, we compare its predictions for the conservative scattering angle, augmented with dissipative contributions, against numerical-relativity data of nonspinning and spinning equal-mass black holes. We observe very good agreement, comparable, and in some cases slightly better to the recently proposed wEOB-potential model, of which the SEOB-PM model is a resummation around the probe limit. Indeed, in the probe limit, the SEOB-PM Hamiltonian and scattering angles reduce to the one of a test mass in Kerr spacetime. Once complemented with nonlocal-in-time contributions for bound orbits, the SEOB-PM Hamiltonian can be utilized to generate waveform models for spinning black holes on quasicircular orbits. Published by the American Physical Society 2024

Correlation function of thin-shell operators

In this study, we explore the correlation functions of thin-shell operators, represented semiclassically by a homogeneous, thin interface of dust particles. Employing the monodromy method, we successfully compute the contribution from the Virasoro vacuum block and present the monodromy equation in a closed form without assuming the probe limit. Although an analytical solution to the monodromy equation remains difficult, we demonstrate that it is perturbatively solvable within specific limits, including the probe limit, the heavy-shell limit, and the early-time limit. Moreover, we compare our results with gravitational calculations and find precise agreement. We strengthen our findings by proving that the thermal correlation functions in gravity, after an inverse Laplace transformation, satisfy the field theory’s monodromy equation. Additionally, we identify an infinite series of unphysical solutions to the monodromy equation and discuss their potential geometrical duals.

Holographic entanglement entropy of disk in insulator/superconductor transition with logarithmic nonlinear electrodynamics

We explore the holographic phase transition with logarithmic nonlinear electrodynamics in the backgrounds of the AdS soliton away from the probe limit. We disclose the properties of phases by the holographic entanglement entropy of disk for the scalar operators. We find that the holographic entanglement entropy is a useful tool to probe the critical chemical potential and the order of the phase transition in the system. In the superconductor phase, the holographic entanglement entropy for scalar operator <O+> has a non-monotonic behavior as the chemical potential increases, while the entanglement entropy for operator <O−> decreases monotonously. With the increase of the logarithmic nonlinear factor b, the holographic entanglement entropy becomes bigger for both scalar operators <O±>. Furthermore, the insulator/superconductor phase transition probed by the entanglement entropy in the holographic system is characterized only by the chemical potential and is independent of the logarithmic nonlinear electrodynamics.

Extremal black hole decay in de Sitter space

The decay of extremal charged black holes has been a useful guidance to derive consistency conditions in quantum gravity. In de Sitter space it has been argued that requiring (extremal) charged Nariai black holes to decay without forming a big crunch singularity yields the Festina Lente (FL) bound: particles with mass ms and charge q should satisfy ms2≫MpHq\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {m}_s^2\\gg {M}_p Hq $$\\end{document}, where Mp is the Planck mass and H the Hubble parameter. Using a tunneling approach we show that the decay probability of charged black holes in de Sitter space in the s-wave sector is P ∼ exp(∆Sb), where ∆Sb is the change in the black hole entropy. We find that the FL bound corresponds to ∆Sb ≤ – 1 in the Nariai and probe limit. However, taking into account backreaction we identify unsuppressed decay channels, which might be subdominant, that violate this bound but nonetheless do not result in a big crunch for every observer.

Fidelity of wormhole teleportation in finite-qubit systems

The rapid development of quantum science and technology is leading us into an era where quantum many-body systems can be comprehended through quantum simulations. Holographic duality, which states gravity and spacetime can emerge from strongly interacting systems, then offers a natural avenue for the experimental study of gravity physics without delving into experimentally infeasible high energies. A prominent example is the simulation of traversable wormholes through the wormhole teleportation protocol, attracting both theoretical and experimental attention. In this work, we develop the theoretical framework for computing the fidelity of wormhole teleportation in N-qubit systems with all-to-all interactions, quantified by mutual information and entanglement negativity. The main technique is the scramblon effective theory, which captures universal out-of-time-order correlations in generic chaotic systems. We clarify that strong couplings between the two systems are essential for simulating the probe limit of semi-classical traversable wormholes using strongly interacting systems with near-maximal chaos. However, the teleportation signal diminishes rapidly when reducing the system size N, requiring a large number of qubits to observe a sharp signature of emergent geometry by simulating the Sachdev-Ye-Kitaev model. This includes both the causal time-order of signals and the asymmetry of the teleportation signal for coupling with different signs. As a comparison, the teleportation signal increases when reducing N in weakly interacting systems. We also analyze the fidelity of the generalized encoding scheme in fermionic string operators.

Mean field theory for strongly coupled systems: Holographic approach

In this paper, we develop the holographic mean field theory for strongly interacting fermion systems. We investigate various types of the symmetry-breakings and their effect on the spectral function. We found analytic expressions of fermion Green’s functions in the probe-limit for all types of tensor order parameter fields. We classified the spectral shapes and singularity types from the analytic Green’s function. We calculated the fermions spectral function in the full backreacted background and then compared it with the analytic results to show the reliability of analytic results in the probe limit. The fact that all the main features of the spectral features in the current condensed matter physics including gaps of s-,p- waves, nodal rings and nodal shells, the flat band of dimension 1,2,3, can be obtained in the absence of the lattice as consequences of the order and symmetry breaking pattern, is a pleaseant surprise.

Hunting for sterile neutrino with future collider signatures

We study the feasibility to observe sterile neutrino at the high energy colliders with direct production channels through e+e−, ep collision, and indirect production channels through decays of heavy meson, baryon and Higgs. For e+e− collision, the e+e−→ν¯eN channel is explored with new signal selection method which tends to be efficient for light mN, the constraints of active-sterile mixing |UeN|2 at the SuperKEKB, CEPC and ILC are expected to reach better lower limits than current experiments. For ep collision, We investigate the heavy sterile neutrino production through a new channel via photon PDF, i.e., e−γ→NW−, hundreds of GeV heavy sterile neutrino can be probe and new limit on mixing is given. For heavy hadrons decay, the lepton-number-violating decays of Λc,Ξc,Ξcc and Λb are explored via an intermediate on-shell Majorana neutrino in GeV scale. The branching fractions and the constraints for |UℓN|2 are given, and hence may put new limits on this mass region. The Higgs→Wμμπ channel is also considered to test massive neutrino within Higgs sector.

More holographic M5 branes in AdS7 × S4

We study classical M5 brane solutions in the probe limit in the AdS7×S4 spacetime geometry with worldvolume 3-form flux. These solutions describe the holography of codimension-4 defects in the 6d boundary dual N=(0,2) supersymmetric gauge theories. Starting from some half-BPS solutions which follow stricter BPS conditions, we find a general 116-BPS solution. We show how some of the giant-like M5 brane solutions here may be related to the codimension-2 surface operators in the 4d gauge theory.

Generalized extremal branes in AdS/CMT and holographic superconductors

AdS4 generalized extremal branes are scrutinized in the context of AdS/CFT. Holographic superconductors are studied as dual objects to AdS4 generalized extremal branes, whose coefficients of response and transport in the dual condensed matter theory are calculated and discussed. The holographic Weyl anomaly is also addressed. The holographic superconductor bound current is shown to be enhanced by the parameter controlling the family of AdS4 generalized extremal branes, when compared to the standard AdS4-Reissner–Nordström black brane results. In the probe limit, the electrical DC conductivity for holographic superconductors with AdS4 generalized extremal branedual background is also reported.

Dynamical evolution of spinodal decomposition in holographic superfluids

We study the nonlinear dynamical evolution of spinodal decomposition in a first-order superfluid phase transition using a simple holographic model in the probe limit. We first confirm the linear stability analysis based on quasinormal modes and verify the existence of a critical length scale related to a gradient instability — negative speed of sound squared — of the superfluid sound mode, which is a consequence of a negative thermodynamic charge susceptibility. We present a comparison between our case and the standard Cahn-Hilliard equation for spinodal instability, in which a critical length scale can be also derived based on a diffusive instability. We then perform several numerical tests which include the nonlinear time evolution directly from an unstable state and fast quenches from a stable to an unstable state in the spinodal region. Our numerical results provide a real time description of spinodal decomposition and phase separation in one and two spatial dimensions. We reveal the existence of four different stages in the dynamical evolution, and characterize their main properties. Finally, we investigate the strength of dynamical heterogeneity using the spatial variance of the local chemical potential and we correlate the latter to other features of the dynamical evolution.

Holographic quantum distances and replica trick

This paper gives concrete examples to exhibit how to use the replica trick to calculate the quantum (quasi-)distances holographically. First, we consider the fidelity and relative entropy between thermal states that are dual to the Schwarzschild-AdS black holes. Then we generalize our method into the RN-AdS black holes by adding a U(1) gauge field. We also investigate the fidelity between states excited by scalar operator in probe limit. In this case, it is surprising that the fidelity in standard quantization will suffer from new UV divergence though the usual holographic renormalization has been applied. We call for deep understanding for such divergence in the future. We also discover a holographic method to check whether the density matrices of two holographic states are commutative.

Thymidine Kinase-Independent Click Chemistry DNADetect Probes for DNA Proliferation Assessment in Malaria Parasites.

Metabolic chemical probes are small-molecule reagents that utilize naturally occurring biosynthetic enzymes for in situ incorporation into biomolecules of interest. These reagents can be used to label, detect, and track important biological processes within living cells including protein synthesis, protein glycosylation, and nucleic acid proliferation. A limitation of current chemical probes, which have largely focused on mammalian cells, is that they often cannot be applied to other organisms due to metabolic differences. For example, the thymidine derivative 5-ethynyl-2'-deoxyuridine (EdU) is a gold standard metabolic chemical probe for assessing DNA proliferation in mammalian cells; however, it is unsuitable for the study of malaria parasites due to Plasmodium species lacking the thymidine kinase enzyme that is essential for metabolism of EdU. Herein, we report the design and synthesis of new thymidine-based probes that sidestep the requirement for a thymidine kinase enzyme in Plasmodium. Two of these DNADetect probes exhibit robust labeling of replicating asexual intraerythrocytic Plasmodium falciparum parasites, as determined by flow cytometry and fluorescence microscopy using copper-catalyzed azide-alkyne cycloaddition to a fluorescent azide. The DNADetect chemical probes are synthetically accessible and thus can be made widely available to researchers as tools to further understand the biology of different Plasmodium species, including laboratory lines and clinical isolates.

Experiments in micro-patterned model membranes support the narrow escape theory

The narrow escape theory (NET) predicts the escape time distribution of Brownian particles confined to a domain with reflecting borders except for one small window. Applications include molecular activation events in cell biology and biophysics. Specifically, the mean first passage time bar{tau } can be analytically calculated from the size of the domain, the escape window, and the diffusion coefficient of the particles. In this study, we systematically tested the NET in a disc by variation of the escape opening. Our model system consisted of micro-patterned lipid bilayers. For the measurement of bar{tau }, we imaged diffusing fluorescently-labeled lipids using single-molecule fluorescence microscopy. We overcame the lifetime limitation of fluorescent probes by re-scaling the measured time with the fraction of escaped particles. Experiments were complemented by matching stochastic numerical simulations. To conclude, we confirmed the NET prediction in vitro and in silico for the disc geometry in the limit of small escape openings, and we provide a straightforward solution to determine bar{tau } from incomplete experimental traces.

Force-free higher derivative Einstein-Maxwell theory and multi-centered black holes

We investigate which 4-derivative extensions of Einstein-Maxwell theory admit multi-extremal black hole solutions with gravitational force balanced by Coulomb force. We obtain a set of constraints on the 4-derivative couplings by exploring various probe limits in multi-black hole systems. It turns out that these constraints are tighter than those needed to protect the mass-charge ratio of extremal black holes from higher derivative corrections. In fact, they are so strong that the Majumdar-Papapetrou multi-black solutions are unmodified by the force-free combinations of the 4-derivative couplings. Explicit examples of such 4-derivative couplings are given in 4-and 5-spacetime dimensions. Interestingly these include curvature-squared supergravity actions and the quasi-topological F4 term.

Free Energy, Stability, and Particle Source in Dynamical Holography

We study dynamical holographic systems and the relation between thermodynamical and dynamical stability of such systems, using the conserved currents in the bulk spacetime. In particular, in the probe limit a generalized free energy is defined with the property of monotonic decreasing in dynamic processes. It is then shown that the (absolute) thermodynamical stability implies the dynamical stability, while the linear dynamical stability implies the thermodynamical (meta-)stability. The holographic superfluid is taken as an example to illustrate our general formalism, where the dynamic evolution of the system in contact with a particle source is clarified by theoretical investigation and numerical verification. The case going beyond the probe limit is also discussed.

Holographic entanglement entropy with Power-Maxwell electrodynamics in higher dimensional AdS black hole spacetime* *Supported by the National Natural Science Foundation of China (11665015), the Guizhou Provincial Science and Technology Planning Project of China (qiankehejichu-ZK[2021]yiban026), and the Guizhou Province ordinary institutions of higher learning top science and technology talents Support plan of China (qianjiaoheKY[2019]062).

We investigate the behaviors of the scalar operator and holographic entanglement entropy in the metal/superconductor phase transition with Power-Maxwell electrodynamics in a higher dimensional background away from the probe limit. We observe that the larger parameters b and q make the condensation of the scalar operator more difficult, and the critical temperature decreases more slowly as the factors increase. In the belt geometry, the value of the entanglement entropy in the metal and superconductor phases is not only related to the the strength of the Power-Maxwell field but also to the width of the strip geometry. At the phase transition point, the discontinuous slope of entanglement entropy is universal for different model factors. It turns out that holographic entanglement entropy is a powerful tool to probe the properties of the phase transition in this holographic superconductor model.

Holographic superfluid with excited states

We construct a novel family of solutions of the holographic superfluid model with the excited states in the probe limit. We observe that the higher excited state or larger superfluid velocity will make the scalar hair more difficult to be developed, and the higher excited state or smaller mass of the scalar field makes it easier for the emergence of translating point from the second-order transition to the first-order one. We note that the difference of the critical chemical potential between the consecutive states increases as the superfluid velocity increases. Interestingly, the “Cave of Winds” phase structure will disappear but the first-order phase transition occurs for the excited states, which is completely different from the holographic superfluid model with the ground state. This means that the excited state will hinder the appearance of the Cave of Winds. Moreover, we find that there exist additional poles in Im[σ(ω)] and delta functions in Re[σ(ω)] arising at low temperature for the excited states, and the higher excited state or larger superfluid velocity results in the larger deviation from the expected relation in the gap frequency.

Inspection for non-planar shaped welded joints of pipes using FMC ultrasonic technique

In applying ultrasonic testing (UT) to pipes with welded joints, one of the challenges is about the access limitation of UT probes caused by non-planar weld reinforcement profiles. One way to avoid this problem is to remove weld reinforcement for ensuring the contactability of a probe on welded parts. However, the removing process for flatten weld reinforcement needs extra day per joint and might damage pipes surface. To overcome this issue, we have been developing a proprietary UT method that enables inspection of non-planar welded joints using the Full Matrix Capture (FMC) and the Total Focusing Method (TFM). A specially designed wedge is used between a probe and a welded part in order to extract the weld surface shape from the recorded data. In the TFM, multilayer propagation paths are analyzed with considering refractions at interfaces between the layer and the weld surface. The analysis is based on the Fermat's principle of least time, whereas this is generally known to be a time-consuming process. With the aim of performing real-time scanning in inspection to pipes on weld reinforcement, the shape of the wedge is optimized for welded joints to reduce the calculation time of the multilayer analysis. In this presentation, we will report the developed FMC/TFM technique and, furthermore, the validation results using pipe specimens with weld reinforcement.

Ultrasound Imaging with Flexible Array Transducer for Pancreatic Cancer Radiation Therapy

Pancreatic cancer with less than 10% 3-year survival rate is one of deadliest cancer types and greatly benefits from enhanced radiotherapy. Organ motion monitoring helps spare the normal tissue from high radiation and, in turn, enables the dose escalation to the target that has been shown to improve the effectiveness of RT by doubling and tripling post-RT survival rate. The flexible array transducer is a novel and promising solution to address the limitation of conventional US probes. We proposed a novel shape estimation for flexible array transducer using two sequential algorithms: (i) an optical tracking-based system that uses the optical markers coordinates attached to the probe at specific positions to estimate the array shape in real-time and (ii) a fully automatic shape optimization algorithm that automatically searches for the optimal array shape that results in the highest quality reconstructed image. We conducted phantom and in vivo experiments to evaluate the estimated array shapes and the accuracy of reconstructed US images. The proposed method reconstructed US images with low full-width-at-half-maximum (FWHM) of the point scatters, correct aspect ratio of the cyst, and high-matching score with the ground truth. Our results demonstrated that the proposed methods reconstruct high-quality ultrasound images with significantly less defocusing and distortion compared with those without any correction. Specifically, the automatic optimization method reduced the array shape estimation error to less than half-wavelength of transmitted wave, resulting in a high-quality reconstructed image.