How can we erase states inside a black hole?

We investigate an entangled system, which is analogous to a composite system of a black hole and Hawking radiation. If Hawking radiation is well approximated by an outgoing particle generated from pair creation around the black hole, such a pair creation increases the total number of states. There should be a unitary mechanism to reduce the number of states inside the horizon for black hole evaporation. Because the infalling antiparticle has negative energy, as long as the infalling antiparticle finds its partner such that the two particles form a separable state, one can trace out such a zero energy system by maintaining unitarity. In this paper, based on some toy model calculations, we show that such a unitary tracing-out process is only possible before the Page time while it is impossible after the Page time. Hence, after the Page time, if we assume that the process is unitary and the Hawking pair forms a separable state, the internal number of states will monotonically increase, which is supported by the Almheiri-Marolf-Polchinski-Sully (AMPS) argument. In addition, the Hawking particles cannot generate randomness of the entire system; hence, the entanglement entropy cannot reach its maximum. Based on these results, we modify the correct form of the Page curve for the remnant picture. The most important conclusion is this: if we assume unitarity, semi-classical quantum field theory, and general relativity, then the black hole should violate the Bekenstein-Hawking entropy bound around the Page time at the latest; hence, the infinite production arguments for remnants might be applied for semi-classical black holes, which seems very problematic.Comment: 18 pages, 7 figure

Plasmodesmal receptor-like kinases identified through analysis of rice cell wall extracted proteins

In plants, plasmodesmata (PD) are intercellular channels that function in both metabolite exchange and the transport of proteins and RNAs. Currently, many of the PD structural and regulatory components remain to be elucidated. Receptor-like kinases (RLKs) belonging to a notably expanded protein family in plants compared to the animal kingdom have been shown to play important roles in plant growth, development, pathogen resistance, and cell death. In this study, cell biological approaches were used to identify potential PD-associated RLK proteins among proteins contained within cell walls isolated from rice callus cultured cells. A total of 15 rice RLKs were investigated to determine their subcellular localization, using an Agrobacterium-mediated transient expression system. Of these six PD-associated RLKs were identified based on their co-localization with a viral movement protein that served as a PD marker, plasmolysis experiments, and subcellular localization at points of wall contact between spongy mesophyll cells. These findings suggest potential PD functions in apoplasmic signaling in response to environmental stimuli and developmental inputs

Neuromatch Academy: a 3-week, online summer school in computational neuroscience

Neuromatch Academy (https://academy.neuromatch.io; (van Viegen et al., 2021)) was designed as an online summer school to cover the basics of computational neuroscience in three weeks. The materials cover dominant and emerging computational neuroscience tools, how they complement one another, and specifically focus on how they can help us to better understand how the brain functions. An original component of the materials is its focus on modeling choices, i.e. how do we choose the right approach, how do we build models, and how can we evaluate models to determine if they provide real (meaningful) insight. This meta-modeling component of the instructional materials asks what questions can be answered by different techniques, and how to apply them meaningfully to get insight about brain function

Universal time delays in the inelastic core level photoemission of metals

Proposing a theoretical model of the core level photoemission of metals, we investigate the plasmon-driven inelastic photoemission delays based on a nonperturbative treatment of many-electron responses due to the long-range Coulomb potential. Being irrelevant to the plasmon coupling strength as well as the plasmon frequency, the emission delays Δτn of the nth-order plasmon satellites (n=1,2,3,...) are found to be universal order by order among the metals in the core level photoemission where the recoil-less approximation would be valid. In particular, for a main line with its weight e-γ, where γ quantifies the plasmon coupling strength, the average inelastic photoemission delay (Δτ) is found to be γ(1-e-γ)-1Δτ1 and thus is simply scaled by a universal time delay Δτ1. This finding is sharply contrasted with the emission delays under the localized potential, which indicates a fundamental difference in the emission process between extended and localized screenings. © 2021 American Physical Society.1

Anisotropic photoelectron emission delay in two-dimensional atomic arrangements

In two-dimensional semiconductors, the density fluctuation potential created by a screening of the photohole is intrinsically anisotropic because of the infinitely periodic planar arrangements of atoms. Modeling the anisotropic-localized screening with the cylindrical geometry, we investigate the emission delay of the photoelectron from 2s and 2pz states of graphene in an angle-resolved mode of the attosecond streaking by solving the time-dependent Schrödinger equation. Strong angle dependencies in absolute emission delays of 2s and 2pz states are obtained, from which the effects of the infrared-induced continuum transition are ruled out and those of the anisotropic screening could be solely extracted. Consequently, the anisotropic scattering induces photoelectrons to be emitted with substantial negative delays within small angles (i.e., θ≲θc) from the normal direction to the atomic arrangement, that is, a conical electron emission in a very early stage of the photoemission. © 2021 American Physical Society.1

Page curves for tripartite systems

We investigate information flow and Page curves for tripartite systems. We prepare a tripartite system (say, A, B, and C) of a given number of states and calculate information and entropy contents by assuming random states. Initially, every particle was in A (this means a black hole), and as time goes on, particles move to either B (this means Hawking radiation) or C (this means a broadly defined remnant, including a non-local transport of information, the last burst, an interior large volume, or a bubble universe, etc). If the final number of states of the remnant is smaller than that of Hawking radiation, then information will be stored by both the radiation and the mutual information between the radiation and the remnant, while the remnant itself does not contain information. On the other hand, if the final number of states of the remnant is greater than that of Hawking radiation, then the radiation contains negligible information, while the remnant and the mutual information between the radiation and the remnant contain information. Unless the number of states of the remnant is large enough compared to the entropy of the black hole, Hawking radiation must contain information; and we meet the menace of black hole complementarity again. Therefore, this contrasts the tension between various assumptions and candidates of the resolution of the information loss problem. © 2017 IOP Publishing Ltd.FALS