From black hole spectral instability to stable observables

The quasi-normal mode (QNM) spectrum of black holes is unstable under small perturbation of the potential and has observational consequences in time signals. Such signals might be experimentally difficult to observe and probing this instability will be a technical challenge. Here we investigate the spectral instability of time-independent data. This leads us to study the Regge Poles (RP), the counterparts to the QNMs in the complex angular momentum plane. We present evidence that the RP spectrum is unstable but that not all overtones are affected equally by this instability. In addition, we reveal that behind this spectral instability lies an underlying structure. The RP spectrum is perturbed in such a way that one can still recover stable scattering quantities using the complex angular momentum approach. Overall, the study proposes a novel and complementary approach on the black hole spectral instability phenomena which allows us to reveal a surprising and unexpected mechanism at play which protects scattering quantities from the instability.Comment: 5 + 3 pages, 4 + 2 figures, 1 table. Title changed. Matches the accepted version in Phys. Rev. Let

Black hole information recovery from gravitational waves

We study the classical and quantum black hole information in gravitational waves from a black hole's history. We review the necessary concepts regarding quantum information in many-body systems to motivate information retrieval and content in gravitational waves. We then show the first step in an optimal information retrieval strategy is to search for information in gravitational waves, compared to searching for correlations in Hawking radiation. We argue a large portion of the information of the initial collapsing state may be in the gravitational waves. Using the Zerilli equation for particles falling radially into Schwarzschild black holes, we then describe a method to retrieve full classical information about infalling sources, including masses, infall times and angles.Comment: 25 pages, 4 figures, 1 table, 1 appendi

Hydrodynamic simulations of rotating black holes

Wave scattering phenomena are ubiquitous in almost all Sciences, from Biology to Physics. Interestingly, it has been shown many times that different physical systems are the stage to the same processes. The discoveries of such analogies have resulted in a better understanding of Physics and are indications of the universality of Nature. One stunning example is the observation that waves propagating on a flowing fluid effectively experience the presence of a curved space-time. In this thesis we will use this analogy to investigate, both theoretically and experimentally, fundamental effects occurring around vortex flows and rotating black holes. In particular, we will focus on light-bending, superradiance scattering, and quasi-normal modes emission. The experimental nature of this work will lead us to study these processes in the presence of dispersive effects. After a general and historical discussion of the field of analogue gravity, we will first present a well-established technique, the gradient expansion method, to obtain approximate solutions of dynamical equations. This method will be used to generalise the notion of light-rings around black holes to vortex flows. Secondly, we will present a wave-vortex scattering experiment in which the superradiance process was observed. Finally, we will relate the properties of the light-rings to the characteristic modes emitted during the relaxation phase of a perturbed vortex flow. We will show that these characteristic modes can be used to develop a flow measurement technique that we call ‘Analogue Black Hole Spectroscopy’. We will then report on an experiment in which these characteristic modes were observed and the analogue black hole spectroscopy technique was applied successfully. Our results strengthen the link between vortices and rotating black holes and open up new challenges to be addressed in the future

Imperfect draining vortex as analogue extreme compact object

Motivated by recent experimental progress, we study scalar wave propagation over an imperfect draining vortex, which can serve as an analogue for rotating and non-rotating extreme compact objects (ECOs). We encapsulate the absorbing properties of the analogue ECO by means of an effective boundary located around the analogue horizon. The presence of reflection at the effective boundary, characterised by a single parameter $\mathcal{K}$, allows for the existence of bound states located between the effective vortex core and the angular momentum barrier. The existence of these bound states leads to an enhanced absorption when the frequency of the incoming wave matches bound state frequencies, which result in Breit-Wigner type spectral lines in the absorption spectra. We also investigate the case of rotating analogue ECOs. In this scenario, some of the bound states undergo superradiant amplification and become unstable. In both the rotating and non-rotating case, we calculate numerically transmission/reflection spectra exhibiting the enhanced absorption/amplification. We complement our numerical study with WKB estimates as well as an extension of the P\"oschl-Teller toy model which we solve analytically. Our simple model exhibits distinctive properties which could be observed in future analogue gravity experiments. We further argue that the observation of the spectral lines could be a way to characterise the effective field theory at play in the vicinity of the vortex core.Comment: 12 pages, 10 figure

From subduction to collision. a combined metamorphic, structural and geochronological study of polymetamorphic metasediments at the NE edge of the Lepontine dome (Swiss Central Alps)

This study analyses the tectono-metamorphic evolution of metasedimentary units belonging to the Valaisan and adjacent European domains at the north-eastern border of the Lepontine dome (Central Alps). The investigated area is characterized by a remarkable metamorphic gradient ranging from subduction-related HP/LT metamorphism in the NE to collision-related Barrovian overprint in the SW. Detailed structural fieldwork and petrological investigations including Raman spectroscopy of carbonaceous matter were carried out in order to reconstruct the tectono-metamorphic evolution on a larger scale. Furthermore, new 40Ar/39Ar dating of white mica and biotite reveal the timing of both subductionrelated high-pressure metamorphism and collision-related Barrovian overprint. The combination of all these investigations allows for deciphering a complete P-T-d-t path (pressure, temperature, deformation and time) of an area that occupies a key position in the Alpine orogenic belt for understanding the transition from subduction to collision. This study documents for the first time that relics of Fe-Mg carpholite indicating blueschist facies conditions occur also within metasedimentary units that are part of the north-eastern Lepontine dome where, so far, exclusively Barrovian assemblages were found. They occur in metasediments from both the Valaisan domain (Grava and Tomül nappes) and parts of the adjacent European domain (Peiden slices and Piz Terri-Lunschania unit). These high-pressure units were subsequently overprinted by a thermal event, as is documented by the growth of new minerals typical for Barrovian metamorphism. The investigated metasediments provide clear evidence for a bimodal P-T path in the north-eastern Lepontine dome characterized by the following polyphase metamorphic evolution: (1) Subductionrelated syn-D1 (Safien phase) HP/LT metamorphism under blueschist facies conditions (350-400 °C and 1.2-1.4 GPa) was established at 42-40 Ma, as revealed by 40Ar/39Ar dating of white mica associated with Fe-Mg carpholite; the early high-pressure event was followed by “cold” isothermal (or cooling) decompression during D2 nappe-stacking (Ferrera phase) for which an age of 36-33 Ma is inferred based on 40 Ar/39Ar dating of white mica replacing Fe-Mg carpholite. (2) Early collision-related greenschist facies overprint (350-425 °C) post-dating substantial decompression and associated D2 deformation was established at 32-29 Ma and affected both HP and LP metasediments. This metamorphic event clearly predates D3 deformation (Domleschg phase, ~25 Ma) as is evidenced by folded isotemperature contours. (3) Collision-related Barrovian overprint (500-590 °C and 0.5-0.8 GPa) represents a second and considerably younger (post 20 Ma) “isobaric” heating pulse only preserved in the SW part of the investigated area. Hence amphibolite facies metamorphism representing the mature stage of a colliding orogen is clearly separated by D2 and D3 deformations, as well as by an intervening greenschist facies event, from the D1 high-pressure stage. Amphibolite facies overprint occurred before and/or during the initial stages of D4 (Chièra phase), representing a second nappe-refolding event. This investigation revealed a significant time gap in the order of some 20 Ma between subductionrelated HP/LT metamorphism and collision-related MP/MT Barrovian overprint. This supports the notion of a polymetamorphic evolution associated with a bimodal P-T path. The results of this study argue that heat release from radioactive decay of vast amounts of accreted continental-derived basement nappes may play an important role in contributing much to heat production needed for amphibolite facies Barrow-type overprint. Based on field evidence, we conclude that heat transfer in the north-eastern Lepontine was essentially conductive during the latest stages of the thermal evolution

Quasinormal Mode Oscillations in an Analogue Black Hole Experiment

The late stages of the relaxation process of a black hole are expected to depend only on its mass and angular momentum and not on the details of its formation process. Inspired by recent analogue gravity experiments, which demonstrate that certain black hole processes take place in gravitational and hydrodynamical systems alike, we conduct an experiment to search for quasinormal mode oscillations of the free surface of a hydrodynamical vortex flow. Our results demonstrate the occurrence and hint at the ubiquity of quasinormal ringing in nonequilibrium analog black hole experiments

Quasinormal Modes of Optical Solitons

Quasinormal modes (QNMs) are essential for understanding the stability and resonances of open systems, with increasing prominence in black hole physics. We present here the first study of QNMs of optical potentials. We show that solitons can support QNMs, deriving a soliton perturbation equation and giving exact analytical expressions for the QNMs of fiber solitons. We discuss the boundary conditions in this intrinsically dispersive system and identify novel signatures of dispersion. From here, we discover a new analogy with astrophysical black holes and describe a regime in which the soliton is a robust black hole simulator for light-ring phenomena. Our results invite a range of applications, from the description of optical pulse propagation with QNMs to the use of state-of-the-art technology from fiber optics to address questions in black hole physics, such as QNM spectral instabilities and the role of nonlinearities in ringdown.Comment: 5 pages, 3 figure

Estrategia para usar racionalmente el agua: experiencia de una entidad de educación técnica industrial, certificada bajo la norma ISO 14001:2004

On the coast of Peru, a region that concentrates 60% of the population and where a very high pressure on water resources exist, is beneficial to the National Service for Industrial Training (SENATI), have a strategy to use the water. To do this, set for its headquarters, located in the district of Independence, three axes to improve water use: Define control mechanisms, using appropriate technologies and maintain an environmental awareness among users. These axes allowed it to reduce wastes at the rate of 20% in the first year of implementation. From then until now, has been instrumental work in raising awareness among users about the importance of rational use of water, in order to continue to maintain average rates of 0,35 m3/person/year.En la costa del Perú, región que concentra al 60% de la población y en donde se ejerce una alta presión sobre el recurso hídrico, resulta beneficioso para el Servicio Nacional de Adiestramiento en Trabajo Industrial (SENATI), contar con una estrategia para usar racionalmente el agua. Para ello, estableció para su sede principal, ubicada en el distrito de Independencia, tres ejes para mejorar el uso del agua: Definir mecanismos de control, usar tecnologías adecuadas y mantener una conciencia ambiental en los usuarios. Estos ejes le permitieron reducir malas prácticas a razón del 20% en el primer año de implementación. Desde entonces y hasta ahora, ha resultado fundamental trabajar en concientizar a los usuarios sobre la importancia del uso racional del agua, con la finalidad de seguir manteniendo ratios promedio de 0,35 m3/persona/año