Generalisations of holographic hydrodynamics

In der vorliegenden Dissertation werden Eigenschaften stark gekoppelter hydrodynamischer Theorien untersucht, die mittels einer dualen Beschreibung als höherdimensionale gravitative Systeme aufgefasst werden können. Besonderes Augenmerk liegt hierbei auf der Berechnung physikalischer Größen wie Viskositäten oder Diffusionskonstanten. Diese werden hinsichtlich der Frage betrachtet, ob sie allgemeingültigen, universellen Gesetzmäßigkeiten folgen, die man aus der Beschreibung mittels einer Gravitationstheorie ableiten kann. Die theoretische Grundlage bildet hierbei die Dualität konformer Quantenfeldtheorien im Minkowski Raum und höherdimensionaler Stringtheorien im Anti-de Sitter Raum, die AdS/CFT Korrespondenz. Einen besonders interessanten Grenzfall stellt der Limes starker Kopplung und hoher Anzahl von Freiheitsgraden der konformen Feldtheorie dar, in dem sich die duale Beschreibung zu klassischer Gravitationstheorie im AdS Raum vereinfacht. Mittels störungstheoretischer Betrachtung der Fluktuationen von Schwarzen Loch Lösungen der Gravitationstheorie lassen sich universelle hydrodynamische Eigenschaften der stark gekoppelten Feldtheorie beschreiben. Eines der Hauptergebnisse dieses Forschungsgebietes ist der Nachweis, dass Fluide, die durch eine einfache duale Gravitationstheorie mit ungebrochener Rotationsinvarianz beschrieben werden können, ein universelles Verhältnis aus Scherviskosität und Entropiedichte besitzen. Erstaunlicherweise stimmt dieses Verhältnis parametrisch mit dem gemessenen Wert des stark gekoppelten Quark-Gluonen-Plasmas überein, ohne dass eine direkte Beschreibung dieser QCD Phase momentan möglich ist. In der vorliegenden Arbeit wird die Konstruktion eines ähnlichen, universellen Zusammenhangs beschrieben. In der hydrodynamischen Beschreibung supersymmetrischen Feldtheorien existiert eine Diffusionskonstante, die, ähnlich der Scherviskosität, den spurfreien Teil der Konstitutivgleichung des Supersymmetriestroms beschreibt. Wir berechnen diese Konstante in supersymmetrischen Theorien allgemeiner Dimension mittels verschiedener unabhängiger Rechnungen. Dazu betrachten wir als duale Gravitationstheorie eine generische Supergravitationstheorie. Die Bewegungsgleichung des zum Supersymmetriestrom dualen Gravitinos in Schwarzen Loch Hintergründen wird gelöst und erlaubt die Berechnung der retardierten Greenschen Funktion des Supersymmetriestroms der Feldtheorie. Diese besitzt einen Pol, der die charakteristische Schalldispersionsrelation des Phoninos beschreibt, des Goldstonefermions spontan gebrochener Supersymmetrie aufgrund endlicher Temperatur. In dieser Dispersionsrelation findet sich die besagte Diffusionskonstante, die sich auch mittels einer neuartigen Kubo-Formel direkt aus der Greenschen Funktion berechnen lässt. Das Hauptergebnis der Arbeit bildet hierbei die Etablierung eines Zusammenhangs dieser Diffusionskonstante und eines universell gültigen Absorptionsquerschnitts auf der dualen Seite der Gravitationstheorie, der die Absorption von Spinoren von einem Schwarzen Loch Hintergrund beschreibt. Eine weitere bedeutende Entwicklung besteht in der Entdeckung eines neuartigen Transportkoeffizienten, der einen beobachtbaren induzierten Strom aufgrund der Vortizität eines Fluids beschreibt. Dieser stellt die klassische Manifestation eines quantenmechanischen Effektes dar, der entsteht, wenn die zugrunde liegende mikroskopische Theorie eine quantenmechanische chirale Anomalie aufweist. Wir untersuchen diesen Effekt mithilfe eines theoretischen Ansatzes, der verschiedene Zugänge zum Verhältnis von Hydrodynamik und Gravitation miteinander vereint. Dazu werden rotierende D3-Branen effektiv als asymptotisch flache Verallgemeinerungen von fünf-dimensionalen AdS Reissner-Nordström Schwarzen Löchern beschrieben. Die Fluktuationen dieses Hintergrundes beschreiben nun eine effektive hydrodynamische Theorie auf einer Fläche in festem Abstand zur Singularität des Schwarzen Lochs, auf der die Fluktuationen Dirichlet Randbedingungen annehmen. Diese Herangehensweise erlaubt es uns den erwähnten Quanteneffekt nicht nur am Rand des AdS Raums zu betrachten, sondern auch am Horizont des Schwarzen Lochs, auf jeder Fläche mit konstantem Radius dazwischen oder sogar im asymptotisch flachen Raum.In the present thesis we study properties of strongly coupled hydrodynamic theories which may be described in terms of a dual higher dimensional gravitational system. Particular attention is given to the computation of physical quantities like the theories' viscosities and diffusion constants. These are analysed with regard to the question of whether they follow generally applicable, universal laws which may be derived from the description in terms of a gravitational theory. The theoretical foundation for this is laid by the duality between conformal quantum field theories in Minkowski space and higher-dimensional string theories on Anti-de Sitter space, the AdS/CFT correspondence. A particularly interesting simplification is given by the limit of strong coupling and large number of degrees of freedom of the conformal field theory in which the dual description reduces to a classical theory of gravity on AdS space. By using a perturbative treatment of fluctuations of the gravitational theory's black hole solutions one may describe universal hydrodynamic properties of the strongly coupled field theory. One of the main results within this area of research is the proof that fluids which may be described by a simple dual gravitational theory with unbroken rotational invariance possess a universal ratio of shear viscosity and entropy density. Astonishingly, this ratio parametrically agrees with the value measured for the strongly-coupled quark gluon plasma, although a direct treatment of this QCD phase is at present not available. In the following work we describe the construction of a similar, universal relation. In the hydrodynamic description of supersymmetric field theories there exists a further diffusion constant which, similarly to the shear viscosity, appears in the traceless part of the constitutive relation of the supersymmetry current. We compute this constant in supersymmetric theories of arbitrary dimension via different independent calculations. For doing so we look at a generic supergravity theory as the gravitational dual. The equation of motion of a gravitino, which is the dual field to the supersymmetry current, is solved in a black hole background and allows for the computation of retarded Green's functions of the field theory's supersymmetry current. This has a pole which describes the characteristic sound dispersion relation of the phonino, the Goldstone fermion of spontaneously broken supersymmetry due to finite temperature. In this dispersion relation we find the aforementioned diffusion constant which we also obtain directly from the correlator via a new Kubo formula. The main result of this project is the establishment of a relation of the supersound diffusion constant and a universally applicable absorption cross section on the dual gravitational side which describes the absorption of spinors by a black hole. A further important development is the discovery of a new transport coefficient which describes the observable current that is induced by the vorticity of a fluid. This illustrates the classical manifestation of a quantum mechanical effect which appears when the underlying microscopic theory possesses a quantum mechanical chiral anomaly. We investigate this effect within a theoretical framework which unifies several different approaches at the interplay of hydrodynamics and gravitational physics. We effectively describe rotating D3-branes as asymptotically flat generalisations of five-dimensional AdS Reissner-Nordström black holes. The fluctuations of this background describe an effective hydrodynamical theory on a surface at a finite distance from the black hole's singularity, on which the fluctuations satisfy Dirichlet boundary conditions. This approach allows us to study the mentioned quantum effect not only at the boundary of AdS space, but also at the black hole's horizon, at a surface in between at finite radius, or even in asymptotically flat space

Generalisations of holographic hydrodynamics

In der vorliegenden Dissertation werden Eigenschaften stark gekoppelter hydrodynamischer Theorien untersucht, die mittels einer dualen Beschreibung als höherdimensionale gravitative Systeme aufgefasst werden können. Besonderes Augenmerk liegt hierbei auf der Berechnung physikalischer Größen wie Viskositäten oder Diffusionskonstanten. Diese werden hinsichtlich der Frage betrachtet, ob sie allgemeingültigen, universellen Gesetzmäßigkeiten folgen, die man aus der Beschreibung mittels einer Gravitationstheorie ableiten kann. Die theoretische Grundlage bildet hierbei die Dualität konformer Quantenfeldtheorien im Minkowski Raum und höherdimensionaler Stringtheorien im Anti-de Sitter Raum, die AdS/CFT Korrespondenz. Einen besonders interessanten Grenzfall stellt der Limes starker Kopplung und hoher Anzahl von Freiheitsgraden der konformen Feldtheorie dar, in dem sich die duale Beschreibung zu klassischer Gravitationstheorie im AdS Raum vereinfacht. Mittels störungstheoretischer Betrachtung der Fluktuationen von Schwarzen Loch Lösungen der Gravitationstheorie lassen sich universelle hydrodynamische Eigenschaften der stark gekoppelten Feldtheorie beschreiben. Eines der Hauptergebnisse dieses Forschungsgebietes ist der Nachweis, dass Fluide, die durch eine einfache duale Gravitationstheorie mit ungebrochener Rotationsinvarianz beschrieben werden können, ein universelles Verhältnis aus Scherviskosität und Entropiedichte besitzen. Erstaunlicherweise stimmt dieses Verhältnis parametrisch mit dem gemessenen Wert des stark gekoppelten Quark-Gluonen-Plasmas überein, ohne dass eine direkte Beschreibung dieser QCD Phase momentan möglich ist. In der vorliegenden Arbeit wird die Konstruktion eines ähnlichen, universellen Zusammenhangs beschrieben. In der hydrodynamischen Beschreibung supersymmetrischen Feldtheorien existiert eine Diffusionskonstante, die, ähnlich der Scherviskosität, den spurfreien Teil der Konstitutivgleichung des Supersymmetriestroms beschreibt. Wir berechnen diese Konstante in supersymmetrischen Theorien allgemeiner Dimension mittels verschiedener unabhängiger Rechnungen. Dazu betrachten wir als duale Gravitationstheorie eine generische Supergravitationstheorie. Die Bewegungsgleichung des zum Supersymmetriestrom dualen Gravitinos in Schwarzen Loch Hintergründen wird gelöst und erlaubt die Berechnung der retardierten Greenschen Funktion des Supersymmetriestroms der Feldtheorie. Diese besitzt einen Pol, der die charakteristische Schalldispersionsrelation des Phoninos beschreibt, des Goldstonefermions spontan gebrochener Supersymmetrie aufgrund endlicher Temperatur. In dieser Dispersionsrelation findet sich die besagte Diffusionskonstante, die sich auch mittels einer neuartigen Kubo-Formel direkt aus der Greenschen Funktion berechnen lässt. Das Hauptergebnis der Arbeit bildet hierbei die Etablierung eines Zusammenhangs dieser Diffusionskonstante und eines universell gültigen Absorptionsquerschnitts auf der dualen Seite der Gravitationstheorie, der die Absorption von Spinoren von einem Schwarzen Loch Hintergrund beschreibt. Eine weitere bedeutende Entwicklung besteht in der Entdeckung eines neuartigen Transportkoeffizienten, der einen beobachtbaren induzierten Strom aufgrund der Vortizität eines Fluids beschreibt. Dieser stellt die klassische Manifestation eines quantenmechanischen Effektes dar, der entsteht, wenn die zugrunde liegende mikroskopische Theorie eine quantenmechanische chirale Anomalie aufweist. Wir untersuchen diesen Effekt mithilfe eines theoretischen Ansatzes, der verschiedene Zugänge zum Verhältnis von Hydrodynamik und Gravitation miteinander vereint. Dazu werden rotierende D3-Branen effektiv als asymptotisch flache Verallgemeinerungen von fünf-dimensionalen AdS Reissner-Nordström Schwarzen Löchern beschrieben. Die Fluktuationen dieses Hintergrundes beschreiben nun eine effektive hydrodynamische Theorie auf einer Fläche in festem Abstand zur Singularität des Schwarzen Lochs, auf der die Fluktuationen Dirichlet Randbedingungen annehmen. Diese Herangehensweise erlaubt es uns den erwähnten Quanteneffekt nicht nur am Rand des AdS Raums zu betrachten, sondern auch am Horizont des Schwarzen Lochs, auf jeder Fläche mit konstantem Radius dazwischen oder sogar im asymptotisch flachen Raum.In the present thesis we study properties of strongly coupled hydrodynamic theories which may be described in terms of a dual higher dimensional gravitational system. Particular attention is given to the computation of physical quantities like the theories' viscosities and diffusion constants. These are analysed with regard to the question of whether they follow generally applicable, universal laws which may be derived from the description in terms of a gravitational theory. The theoretical foundation for this is laid by the duality between conformal quantum field theories in Minkowski space and higher-dimensional string theories on Anti-de Sitter space, the AdS/CFT correspondence. A particularly interesting simplification is given by the limit of strong coupling and large number of degrees of freedom of the conformal field theory in which the dual description reduces to a classical theory of gravity on AdS space. By using a perturbative treatment of fluctuations of the gravitational theory's black hole solutions one may describe universal hydrodynamic properties of the strongly coupled field theory. One of the main results within this area of research is the proof that fluids which may be described by a simple dual gravitational theory with unbroken rotational invariance possess a universal ratio of shear viscosity and entropy density. Astonishingly, this ratio parametrically agrees with the value measured for the strongly-coupled quark gluon plasma, although a direct treatment of this QCD phase is at present not available. In the following work we describe the construction of a similar, universal relation. In the hydrodynamic description of supersymmetric field theories there exists a further diffusion constant which, similarly to the shear viscosity, appears in the traceless part of the constitutive relation of the supersymmetry current. We compute this constant in supersymmetric theories of arbitrary dimension via different independent calculations. For doing so we look at a generic supergravity theory as the gravitational dual. The equation of motion of a gravitino, which is the dual field to the supersymmetry current, is solved in a black hole background and allows for the computation of retarded Green's functions of the field theory's supersymmetry current. This has a pole which describes the characteristic sound dispersion relation of the phonino, the Goldstone fermion of spontaneously broken supersymmetry due to finite temperature. In this dispersion relation we find the aforementioned diffusion constant which we also obtain directly from the correlator via a new Kubo formula. The main result of this project is the establishment of a relation of the supersound diffusion constant and a universally applicable absorption cross section on the dual gravitational side which describes the absorption of spinors by a black hole. A further important development is the discovery of a new transport coefficient which describes the observable current that is induced by the vorticity of a fluid. This illustrates the classical manifestation of a quantum mechanical effect which appears when the underlying microscopic theory possesses a quantum mechanical chiral anomaly. We investigate this effect within a theoretical framework which unifies several different approaches at the interplay of hydrodynamics and gravitational physics. We effectively describe rotating D3-branes as asymptotically flat generalisations of five-dimensional AdS Reissner-Nordström black holes. The fluctuations of this background describe an effective hydrodynamical theory on a surface at a finite distance from the black hole's singularity, on which the fluctuations satisfy Dirichlet boundary conditions. This approach allows us to study the mentioned quantum effect not only at the boundary of AdS space, but also at the black hole's horizon, at a surface in between at finite radius, or even in asymptotically flat space

Fluxbrane Inflation

As a first step towards inflation in genuinely F-theoretic setups, we propose a scenario where the inflaton is the relative position of two 7-branes on holomorphic 4-cycles. Non-supersymmetric gauge flux induces an attractive inter-brane potential. The latter is sufficiently flat in the supergravity regime of large volume moduli. Thus, in contrast to brane-antibrane inflation, fluxbrane inflation does not require warping. We calculate the inflaton potential both in the supergravity approximation and via an open-string one-loop computation on toroidal backgrounds. This leads us to propose a generalisation to genuine Calabi-Yau manifolds. We also comment on competing F-term effects. The end of inflation is marked by the condensation of tachyonic recombination fields between the 7-branes, triggering the formation of a bound state described as a stable extension along the 7-brane divisor. Hence our model fits in the framework of hybrid D-term inflation. We work out the main phenomenological properties of our D-term inflaton potential. In particular, our scenario of D7/D7 inflation avoids the familiar observational constraints associated with cosmic strings.Comment: 49 pages, 3 figures; v3: refs adde

Abnormal ECG Findings in Athletes: Clinical Evaluation and Considerations.

PURPOSE OF REVIEW: Pre-participation cardiovascular evaluation with electrocardiography is normal practice for most sporting bodies. Awareness about sudden cardiac death in athletes and recognizing how screening can help identify vulnerable athletes have empowered different sporting disciplines to invest in the wellbeing of their athletes. RECENT FINDINGS: Discerning physiological electrical alterations due to athletic training from those representing cardiac pathology may be challenging. The mode of investigation of affected athletes is dependent on the electrical anomaly and the disease(s) in question. This review will highlight specific pathological ECG patterns that warrant assessment and surveillance, together with an in-depth review of the recommended algorithm for evaluation

Autonomic modulation and antiarrhythmic therapy in a model of long QT syndrome type 3

AIMS: Clinical observations in patients with long QT syndrome carrying sodium channel mutations (LQT3) suggest that bradycardia caused by parasympathetic stimulation may provoke torsades de pointes (TdP). beta-Adrenoceptor blockers appear less effective in LQT3 than in other forms of the disease. METHODS AND RESULTS: We studied effects of autonomic modulation on arrhythmias in vivo and in vitro and quantified sympathetic innervation by autoradiography in heterozygous mice with a knock-in deletion (DeltaKPQ) in the Scn5a gene coding for the cardiac sodium channel and increased late sodium current (LQT3 mice). Cholinergic stimulation by carbachol provoked bigemini and TdP in freely roaming LQT3 mice. No arrhythmias were provoked by physical stress, mental stress, isoproterenol, or atropine. In isolated, beating hearts, carbachol did not prolong action potentials per se, but caused bradycardia and rate-dependent action potential prolongation. The muscarinic inhibitor AFDX116 prevented effects of carbachol on heart rate and arrhythmias. beta-Adrenoceptor stimulation suppressed arrhythmias, shortened rate-corrected action potential duration, increased rate, and minimized difference in late sodium current between genotypes. beta-Adrenoceptor density was reduced in LQT3 hearts. Acute beta-adrenoceptor blockade by esmolol, propranolol or chronic propranolol in vivo did not suppress arrhythmias. Chronic flecainide pre-treatment prevented arrhythmias (all P < 0.05). CONCLUSION: Cholinergic stimulation provokes arrhythmias in this model of LQT3 by triggering bradycardia. beta-Adrenoceptor density is reduced, and beta-adrenoceptor blockade does not prevent arrhythmias. Sodium channel blockade and beta-adrenoceptor stimulation suppress arrhythmias by shortening repolarization and minimizing difference in late sodium current.status: publishe

Genome-wide association analyses identify new Brugada syndrome risk loci and highlight a new mechanism of sodium channel regulation in disease susceptibility

Brugada syndrome (BrS) is a cardiac arrhythmia disorder associated with sudden death in young adults. With the exception of SCN5A, encoding the cardiac sodium channel NaV1.5, susceptibility genes remain largely unknown. Here we performed a genome-wide association meta-analysis comprising 2,820 unrelated cases with BrS and 10,001 controls, and identified 21 association signals at 12 loci (10 new). Single nucleotide polymorphism (SNP)-heritability estimates indicate a strong polygenic influence. Polygenic risk score analyses based on the 21 susceptibility variants demonstrate varying cumulative contribution of common risk alleles among different patient subgroups, as well as genetic associations with cardiac electrical traits and disorders in the general population. The predominance of cardiac transcription factor loci indicates that transcriptional regulation is a key feature of BrS pathogenesis. Furthermore, functional studies conducted on MAPRE2, encoding the microtubule plus-end binding protein EB2, point to microtubule-related trafficking effects on NaV1.5 expression as a new underlying molecular mechanism. Taken together, these findings broaden our understanding of the genetic architecture of BrS and provide new insights into its molecular underpinnings

Transethnic Genome-Wide Association Study Provides Insights in the Genetic Architecture and Heritability of Long QT Syndrome

BACKGROUND: Long QT syndrome (LQTS) is a rare genetic disorder and a major preventable cause of sudden cardiac death in the young. A causal rare genetic variant with large effect size is identified in up to 80% of probands (genotype positive) and cascade family screening shows incomplete penetrance of genetic variants. Furthermore, a proportion of cases meeting diagnostic criteria for LQTS remain genetically elusive despite genetic testing of established genes (genotype negative). These observations raise the possibility that common genetic variants with small effect size contribute to the clinical picture of LQTS. This study aimed to characterize and quantify the contribution of common genetic variation to LQTS disease susceptibility. METHODS: We conducted genome-wide association studies followed by transethnic meta-analysis in 1656 unrelated patients with LQTS of European or Japanese ancestry and 9890 controls to identify susceptibility single nucleotide polymorphisms. We estimated the common variant heritability of LQTS and tested the genetic correlation between LQTS susceptibility and other cardiac traits. Furthermore, we tested the aggregate effect of the 68 single nucleotide polymorphisms previously associated with the QT-interval in the general population using a polygenic risk score. RESULTS: Genome-wide association analysis identified 3 loci associated with LQTS at genome-wide statistical significance (P&lt;5×10-8) near NOS1AP, KCNQ1, and KLF12, and 1 missense variant in KCNE1(p.Asp85Asn) at the suggestive threshold (P&lt;10-6). Heritability analyses showed that ≈15% of variance in overall LQTS susceptibility was attributable to common genetic variation (h2SNP 0.148; standard error 0.019). LQTS susceptibility showed a strong genome-wide genetic correlation with the QT-interval in the general population (rg=0.40; P=3.2×10-3). The polygenic risk score comprising common variants previously associated with the QT-interval in the general population was greater in LQTS cases compared with controls (P&lt;10-13), and it is notable that, among patients with LQTS, this polygenic risk score was greater in patients who were genotype negative compared with those who were genotype positive (P&lt;0.005). CONCLUSIONS: This work establishes an important role for common genetic variation in susceptibility to LQTS. We demonstrate overlap between genetic control of the QT-interval in the general population and genetic factors contributing to LQTS susceptibility. Using polygenic risk score analyses aggregating common genetic variants that modulate the QT-interval in the general population, we provide evidence for a polygenic architecture in genotype negative LQTS.</p