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"Ramirez, M."
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Chaos and pole skipping in CFT2
A
bstract
Recent work has suggested an intriguing relation between quantum chaos and energy density correlations, known as pole skipping. We investigate this relationship in two dimensional conformal field theories on a finite size spatial circle by studying the thermal energy density retarded two-point function on a torus. We find that the location
ω
*
= i
λ
of pole skipping in the complex frequency plane is determined by the central charge and the stress energy one-point function 〈
T
〉 on the torus. In addition, we find a bound on
λ
in
c
> 1 compact, unitary CFT
2
s identical to the chaos bound,
λ
≤ 2
πT
. This bound is saturated in large
c
CFT
2
s with a sparse light spectrum, as quantified by [
1
], for all temperatures above the dual Hawking-Page transition temperature.
Journal Article
Black hole shadow of a rotating polytropic black hole by the Newman–Janis algorithm without complexification
In this work, starting from a spherically symmetric polytropic black hole, a rotating solution is obtained by following the Newman–Janis algorithm without complexification. Besides studying the horizon, the static conditions and causality issues of the rotating solution, we obtain and discuss the shape of its shadow. Some other physical features as the Hawking temperature and emission rate of the rotating polytropic black hole solution are also discussed.
Journal Article
Surfactants: physicochemical interactions with biological macromolecules
Macromolecules are essential cellular components in biological systems responsible for performing a large number of functions that are necessary for growth and perseverance of living organisms. Proteins, lipids and carbohydrates are three major classes of biological macromolecules. To predict the structure, function, and behaviour of any cluster of macromolecules, it is necessary to understand the interaction between them and other components through basic principles of chemistry and physics. An important number of macromolecules are present in mixtures with surfactants, where a combination of hydrophobic and electrostatic interactions is responsible for the specific properties of any solution. It has been demonstrated that surfactants can help the formation of helices in some proteins thereby promoting protein structure formation. On the other hand, there is extensive research towards the use of surfactants to solubilize drugs and pharmaceuticals; therefore, it is evident that the interaction between surfactants with macromolecules is important for many applications which includes environmental processes and the pharmaceutical industry. In this review, we describe the properties of different types of surfactants that are relevant for their physicochemical interactions with biological macromolecules, from macromolecules–surfactant complexes to hydrophobic and electrostatic interactions.
Journal Article
A More Comprehensive Habitable Zone for Finding Life on Other Planets
The habitable zone (HZ) is the circular region around a star(s) where standing bodies of water could exist on the surface of a rocky planet. Space missions employ the HZ to select promising targets for follow-up habitability assessment. The classical HZ definition assumes that the most important greenhouse gases for habitable planets orbiting main-sequence stars are CO2 and H2O. Although the classical HZ is an effective navigational tool, recent HZ formulations demonstrate that it cannot thoroughly capture the diversity of habitable exoplanets. Here, I review the planetary and stellar processes considered in both classical and newer HZ formulations. Supplementing the classical HZ with additional considerations from these newer formulations improves our capability to filter out worlds that are unlikely to host life. Such improved HZ tools will be necessary for current and upcoming missions aiming to detect and characterize potentially habitable exoplanets.
Journal Article
A Complex Life Habitable Zone Based On Lipid Solubility Theory
To find potentially habitable exoplanets, space missions employ the habitable zone (HZ), which is the region around a star (or multiple stars) where standing bodies of water could exist on the surface of a rocky planet. Follow-up atmospheric characterization could yield biosignatures signifying life. Although most iterations of the HZ are agnostic regarding the nature of such life, a recent study argues that a complex life HZ would be considerably smaller than that used in classical definitions. Here, I use an advanced energy balance model to show that such an HZ would be considerably wider than originally predicted given revised CO
2
limits and (for the first time) N
2
respiration limits for complex life. The width of this complex life HZ (CLHZ) increases by ~35% from ~0.95–1.2 AU to 0.95–1.31 AU in our solar system. Similar extensions are shown for stars with stellar effective temperatures between 2,600–9,000 K. I define this CLHZ using lipid solubility theory, diving data, and results from animal laboratory experiments. I also discuss implications for biosignatures and technosignatures. Finally, I discuss the applicability of the CLHZ and other HZ variants to the search for both simple and complex life.
Journal Article
An evidence review of face masks against COVID-19
The science around the use of masks by the public to impede COVID-19 transmission is advancing rapidly. In this narrative review, we develop an analytical framework to examine mask usage, synthesizing the relevant literature to inform multiple areas: population impact, transmission characteristics, source control, wearer protection, sociological considerations, and implementation considerations. A primary route of transmission of COVID-19 is via respiratory particles, and it is known to be transmissible from presymptomatic, paucisymptomatic, and asymptomatic individuals. Reducing disease spread requires two things: limiting contacts of infected individuals via physical distancing and other measures and reducing the transmission probability per contact. The preponderance of evidence indicates that mask wearing reduces transmissibility per contact by reducing transmission of infected respiratory particles in both laboratory and clinical contexts. Public mask wearing is most effective at reducing spread of the virus when compliance is high. Given the current shortages of medical masks, we recommend the adoption of public cloth mask wearing, as an effective form of source control, in conjunction with existing hygiene, distancing, and contact tracing strategies. Because many respiratory particles become smaller due to evaporation, we recommend increasing focus on a previously overlooked aspect of mask usage: mask wearing by infectious people (“source control”) with benefits at the population level, rather than only mask wearing by susceptible people, such as health care workers, with focus on individual outcomes. We recommend that public officials and governments strongly encourage the use of widespread face masks in public, including the use of appropriate regulation.
Journal Article
Patch type nucleotide sequence identities between genomes from many different species facilitate illegitimate recombination
Comparative analyses of nucleotide sequences across diverse taxa, including viruses, bacteria, plants, and mammals, consistently reveal patch-type sequence identities of around 45%. These identities consist of short stretches interspersed by mismatches. Similarly, identity patterns emerge in alignments of randomized shuffled or scrambled sequences. These findings suggest patch-type identities reflect intrinsic statistical properties of the four-letter genetic alphabet. Such patterns likely function as recognition signals for illegitimate recombination, a mechanism that promotes sequence insertions, exchanges, and rearrangements without extensive homology. Patch-type identities have been observed at integration sites of foreign DNA and may play a role in evolutionary innovation and rapid diversification (e. g.
SARS-CoV-2)
. Simulation data support the ideas that the frequency and length distribution of matching segments can be predicted by statistical models based on base composition, yet may also create local environments conducive to recombination. Further, the statistical architecture of the genetic alphabet encodes not only biological information, but also the potential for genome remodeling and adaptation during evolution. By bridging fundamental sequence properties with biological outcomes, this study provides a framework for exploring how randomness at the nucleotide sequence level can give rise to order and complexity across the tree of life.
Journal Article
Association of European Border Regions (AEBR)
AEBR is one of the oldest regional associations in Europe (founded in 1971), with a hundred members (border and cross-border regions) in more than thirty European countries. AEBR works for the interest of border regions towards EU and national authorities, developing capacities, increasing awareness, organizing events and implementing projects. AEBR currently implements IVY (Interreg Volunteer Youth) on behalf of the European Commission's DG Regio, within the framework of the European Solidarity Corps, which has deployed more than 700 young Europeans in Interreg programmes and projects during the last four years. It also manages b-solutions to tackle cross-border legal and administrative obstacles and test possible solutions, and takes part in other projects in Europe and other continents. It has recently finished a study for DG SANTE on cross-border patients’ flows in various EU cross-border areas. The association will be presented by it's Secretary General, Martin Guillermo-Ramírez.
Journal Article
Closure of the operator product expansion in the non-unitary bootstrap
A
bstract
We use the numerical conformal bootstrap in two dimensions to search for finite, closed sub-algebras of the operator product expansion (OPE), without assuming unitarity. We find the minimal models as special cases, as well as additional lines of solutions that can be understood in the Coulomb gas formalism. All the solutions we find that contain the vacuum in the operator algebra are cases where the external operators of the bootstrap equation are degenerate operators, and we argue that this follows analytically from the expressions in
arXiv:1202.4698
for the crossing matrices of Virasoro conformal blocks. Our numerical analysis is a special case of the “Gliozzi” bootstrap method, and provides a simpler setting in which to study technical challenges with the method.
In the supplementary material, we provide a Mathematica notebook that automates the calculation of the crossing matrices and OPE coefficients for degenerate operators using the formulae of Dotsenko and Fateev.
Journal Article