Non-relativistic metrics from back-reacting fermions

It has recently been pointed out that under certain circumstances the back-reaction of charged, massive Dirac fermions causes important modifications to AdS_2 spacetimes arising as the near horizon geometry of extremal black holes. In a WKB approximation, the modified geometry becomes a non-relativistic Lifshitz spacetime. In three dimensions, it is known that integrating out charged, massive fermions gives rise to gravitational and Maxwell Chern-Simons terms. We show that Schrodinger (warped AdS_3) spacetimes exist as solutions to a gravitational and Maxwell Chern-Simons theory with a cosmological constant. Motivated by this, we look for warped AdS_3 or Schrodinger metrics as exact solutions to a fully back-reacted theory containing Dirac fermions in three and four dimensions. We work out the dynamical exponent in terms of the fermion mass and generalize this result to arbitrary dimensions.Comment: 26 pages, v2: typos corrected, references added, minor change

Cooperation between SSTC NRS and the EU in the Area of Nuclear Safety

The paper first briefly outlines the main characteristics of the EU assistance programs aimed to enhance nuclear safety in the Beneficiary countries. Then EU assistance provided to the Ukrainian regulator (SNRIU) is detailed, with specific emphasis on projects enhancing the capabilities of SSTC NRS as technical support organisation (TSO) to SNRIU, including training and tutoring (T&T) activities. The changing role of SSTC NRS in the cooperation activities is described as well. The broad range of cooperation is then illustrated by some selected projects focusing on various technical areas (e.g. severe accident management and mitigation, radioactive waste and spent fuel management, NPP service time extension, plant performance monitoring and operating experience feedback). Finally, the paper briefly discusses the future perspectives of the nuclear safety cooperation between the EU and UkraineНа початку статті коротко викладені основні характеристики програм підтримки ЄС, спрямованих на підвищення ядерної безпеки в країнах-бенефіціарах. Далі детально описується підтримка ЄС, що надається українському регулюючому органу (ДІЯРУ) з акцентом на проекти, спрямовані на розширення можливостей ДНТЦ ЯРБ як організації технічної підтримки (ОТП) ДІЯРУ, охоплюючи навчання і наставництво. Описується зміна ролі ДНТЦ ЯРБ у заходах зі співробітництва, широкий спектр співпраці в рамках деяких вибраних проектів з акцентом на різні технічні області (наприклад, управління важкими аваріями і пом’якшення наслідків, поводження з радіоактивними відходами та відпрацьованим паливом, продовження терміну експлуатації АЕС, контроль робочих характеристик станції та обмін досвідом експлуатації). Стисло обговорюються майбутні перспективи співпраці ЄС та України у сфері ядерної безпеки.В начале статьи кратко изложены основные характеристики программ поддержки ЕС, направленных на повышение ядерной безопасности в странах-бенефициарах. Далее подробно описывается поддержка ЕС, предоставляется украинском регулирующему органу (ГИЯРУ) с акцентом на проекты, направленные на расширение возможностей ГНТЦ ЯРБ как организации технической поддержки (ОТП) ГИЯРУ, включая обучение и наставничество. Описывается изменение роли ГНТЦ ЯРБ в мероприятиях по сотрудничеству, широкий спектр сотрудничества в рамках некоторых выбранных проектов с акцентом на различные технические области (например, управление тяжелыми авариями и смягчения последствий, обращение с радиоактивными отходами и отработанным топливом, продление срока эксплуатации АЭС, контроль рабочих характеристик станции и обмен опытом эксплуатации). Кратко обсуждаются будущие перспективы сотрудничества ЕС и Украины в сфере ядерной безопасности

Magnetic Field Induced Quantum Criticality via new Asymptotically AdS_5 Solutions

Using analytical methods, we derive and extend previously obtained numerical results on the low temperature properties of holographic duals to four-dimensional gauge theories at finite density in a nonzero magnetic field. We find a new asymptotically AdS_5 solution representing the system at zero temperature. This solution has vanishing entropy density, and the charge density in the bulk is carried entirely by fluxes. The dimensionless magnetic field to charge density ratio for these solutions is bounded from below, with a quantum critical point appearing at the lower bound. Using matched asymptotic expansions, we extract the low temperature thermodynamics of the system. Above the critical magnetic field, the low temperature entropy density takes a simple form, linear in the temperature, and with a specific heat coefficient diverging at the critical point. At the critical magnetic field, we derive the scaling law s ~ T^{1/3} inferred previously from numerical analysis. We also compute the full scaling function describing the region near the critical point, and identify the dynamical critical exponent: z=3. These solutions are expected to holographically represent boundary theories in which strongly interacting fermions are filling up a Fermi sea. They are fully top-down constructions in which both the bulk and boundary theories have well known embeddings in string theory.Comment: 50 page

Landau Levels, Magnetic Fields and Holographic Fermi Liquids

We further consider a probe fermion in a dyonic black hole background in anti-de Sitter spacetime, at zero temperature, comparing and contrasting two distinct classes of solution that have previously appeared in the literature. Each class has members labeled by an integer n, corresponding to the n-th Landau level for the fermion. Our interest is the study of the spectral function of the fermion, interpreting poles in it as indicative of quasiparticles associated with the edge of a Fermi surface in the holographically dual strongly coupled theory in a background magnetic field H at finite chemical potential. Using both analytical and numerical methods, we explicitly show how one class of solutions naturally leads to an infinite family of quasiparticle peaks, signaling the presence of a Fermi surface for each level n. We present some of the properties of these peaks, which fall into a well behaved pattern at large n, extracting the scaling of Fermi energy with n and H, as well as the dispersion of the quasiparticles.Comment: 23 pages, 4 figures. Changed some of the terminology: non-separable -> infinite-sum. Clarified the relationship between our ansatz and the separable ansat

Evolution of Holographic Entanglement Entropy after Thermal and Electromagnetic Quenches

We study the evolution and scaling of the entanglement entropy after two types of quenches for a 2+1 field theory, using holographic techniques. We study a thermal quench, dual to the addition of a shell of uncharged matter to four dimensional Anti-de Sitter (AdS_4) spacetime, and study the subsequent formation of a Schwarzschild black hole. We also study an electromagnetic quench, dual to the addition of a shell of charged sources to AdS_4, following the subsequent formation of an extremal dyonic black hole. In these backgrounds we consider the entanglement entropy of two types of geometries, the infinite strip and the round disc, and find distinct behavior for each. Some of our findings naturally supply results analogous to observations made in the literature for lower dimensions, but we also uncover several new phenomena, such as (in some cases) a discontinuity in the time derivative of the entanglement entropy as it nears saturation, and for the electromagnetic quench, a logarithmic growth in the entanglement entropy with time for both the disc and strip, before settling to saturation.Comment: 30 pages, 19 figures. Corrected typos and added some discussion. To appear in New J. Phy

Deconstructing holographic liquids

We argue that there exist simple effective field theories describing the long-distance dynamics of holographic liquids. The degrees of freedom responsible for the transport of charge and energy-momentum are Goldstone modes. These modes are coupled to a strongly coupled infrared sector through emergent gauge and gravitational fields. The IR degrees of freedom are described holographically by the near-horizon part of the metric, while the Goldstone bosons are described by a field-theoretical Lagrangian. In the cases where the holographic dual involves a black hole, this picture allows for a direct connection between the holographic prescription where currents live on the boundary, and the membrane paradigm where currents live on the horizon. The zero-temperature sound mode in the D3-D7 system is also re-analyzed and re-interpreted within this formalism.Comment: 21 pages, 2 figure

A conical deficit in the AdS4/CFT3 correspondence

Inspired by the AdS/CFT correspondence we propose a new duality that allow the study of strongly coupled field theories living in a 2+1 conical space-time. Solving the 4-d Einstein equations in the presence of an infinite static string and negative cosmological constant we obtain a conical AdS4 space-time whose boundary is identified with the 2+1 cone found by Deser, Jackiw and 't Hooft. Using the AdS4/CFT3 correspondence we calculate retarded Green's functions of scalar operators living in the cone.Comment: v3, 14 pages. We reinterpret our results for the Green's functions in the con

Molecular and cognitive signatures of ageing partially restored through synthetic delivery of IL2 to the brain

Cognitive decline is a common pathological outcome during aging, with an ill-defined molecular and cellular basis. In recent years, the concept of inflammaging, defined as a low-grade inflammation increasing with age, has emerged. Infiltrating T cells accumulate in the brain with age and may contribute to the amplification of inflammatory cascades and disruptions to the neurogenic niche observed with age. Recently, a small resident population of regulatory T cells has been identified in the brain, and the capacity of IL2-mediated expansion of this population to counter neuroinflammatory disease has been demonstrated. Here, we test a brain-specific IL2 delivery system for the prevention of neurological decline in aging mice. We identify the molecular hallmarks of aging in the brain glial compartments and identify partial restoration of this signature through IL2 treatment. At a behavioral level, brain IL2 delivery prevented the age-induced defect in spatial learning, without improving the general decline in motor skill or arousal. These results identify immune modulation as a potential path to preserving cognitive function for healthy aging.The work was supported by the Wellcome Trust (222442/Z/21/Z to AL), anERC Consolidator Grant TissueTreg (to A.L.), an ERC Proof of Concept GrantTreatBrainDamage (to A.L.), FWO Research Grant1503420N (to E.P.), anSAO-FRA pilot grant (20190032, to E.P.), an ERC Starting Grant AstroFunc(to M.G.H.), ERC Proof of Concept Grant AD-VIP (to M.G.H.), ERA ChairNCBio (to M.G.H.), and the Biotechnology and Biological Sciences ResearchCouncil through Institute Strategic Program Grant funding BBS/E/B/000C0427and BBS/E/B/000C0428, and the Biotechnology and BiologicalSciences Research Council Core Capability Grant to the BabrahamInstitute. E.P. was supported by a fellowship from the FWO. The authorsacknowledge the important contributions of Jeason Haughton (VIB) formouse husbandry, Pier-Andr ee Penttila and the KUL FACS Core, and theVIB Single Cell Sequencing Core. The visual abstract was created with BioRender.com

Strange metals and the AdS/CFT correspondence

I begin with a review of quantum impurity models in condensed matter physics, in which a localized spin degree of freedom is coupled to an interacting conformal field theory in d = 2 spatial dimensions. Their properties are similar to those of supersymmetric generalizations which can be solved by the AdS/CFT correspondence; the low energy limit of the latter models is described by a AdS2 geometry. Then I turn to Kondo lattice models, which can be described by a mean- field theory obtained by a mapping to a quantum impurity coupled to a self-consistent environment. Such a theory yields a 'fractionalized Fermi liquid' phase of conduction electrons coupled to a critical spin liquid state, and is an attractive mean-field theory of strange metals. The recent holographic description of strange metals with a AdS2 x R2 geometry is argued to be related to such mean-field solutions of Kondo lattice models.Comment: 19 pages, 4 figures; Plenary talk at Statphys24, Cairns, Australia, July 2010; (v2) added refs; (v3) more ref

The Conjugation of Antibodies for the Simultaneous Detection of Surface Proteins and Transcriptome Analysis at a Single-Cell Level

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