The large charge expansion and AdS/CFT

The scaling dimensions of charged operators in conformal field theory were recently computed in a large charge expansion. We verify this expansion in a dual AdS model. Specifically, we numerically construct solitonic boson star solutions of Einstein-Maxwell-Scalar theory in AdS$_4$ and find that its mass at large charge reproduces the universal form of the lowest operator dimension in the large U(1) charge sector of the dual 2+1 dimensional CFT

Are we losing it? Exploring subsoil organic carbon dynamics in a warming world on the molecular level

Soils store around 1500-2400Gt carbon, half of which is stored in subsoils – here defined as soil below 20cm depth. The carbon in soils accounts for two to three times the amount stored in the atmosphere, making soils a highly relevant carbon pool in the global carbon cycle. Soils are expected to experience unprecedented warming throughout the whole profiles with only a slight delay to the surface air temperature. As temperature affects any (bio)chemical reaction, fluxes of carbon between soils and the atmosphere will change. If warming stimulates microbial activity, inducing losses of carbon from soils to the atmosphere and plant inputs of carbon to soils can’t compensate for this loss, atmospheric carbon concentrations will increase. Recent experiments warming the subsoil indicate that the temperature sensitivity of microbial respiration is similar throughout whole soil profiles. Thus, also the large subsoil organic carbon pool is vulnerable to decomposition under global warming. However, we know very little about processes governing subsoil carbon dynamics under warming, which might be markedly different compared to topsoils. This limits predictions about the magnitude and duration of potential releases of subsoil organic carbon to the atmosphere. The magnitude and duration of microbial respiration might be controlled by carbon availability and/or adaptation of the microorganisms to the new environmental conditions. How these processes balance out in subsoil is largely unknown. Furthermore, it is unclear whether microorganisms will feed on any molecular organic carbon compounds in soils or whether specific compounds could be more resistant to degradation under warming. To address these knowledge gaps, this thesis makes use of a novel experimental setup at Blodgett Experimental Forest, CA, USA, which continuously warms soils to 1m depth, considering vertical and seasonal gradients in temperature. The aim of this thesis was to explore subsoil carbon dynamics in a warming world on the molecular level, with a focus on the microbial response and the vulnerability of various molecular compounds to warming induced degradation. In this thesis I highlight that subsoil carbon dynamics might respond to warming more quickly as compared to topsoils. Microbial abundance decreased by -28±9% in warmed subsoil, but was not affected in topsoil. Lower microbial abundance in subsoil was accompanied by changes in microbial physiology and community composition. Lower microbial abundance did not cause a decrease in soil respiration, which was continually elevated. Thus, the smaller microbial community might have adapted to the lower carbon concentrations and quality, using the carbon less efficiently and releasing proportionally more carbon to the atmosphere. Microorganisms did not only degrade simple molecular structures, but also complex polymers such as hydrolysable lipids (-28±3%), lignin phenols (-17±0%) and pyrogenic carbon (-37±8%) were lost from warmed subsoils. These results show that plant polymers and pyrogenic carbon are equally vulnerable to degradation like bulk soil organic carbon in the subsoils studied in this thesis. On the one hand, this could be because complex plant polymers are often not stabilized on mineral surfaces and thus accessible to microbial degradation. On the other hand, degradation of polymers might be especially stimulated by warming because the multiple enzymatic steps needed for the degradation are facilitated by higher temperatures. These results propose that there might not be specific ‘heat-proof compounds’ in (sub)soil but that persistence of soil organic carbon under global warming depends on multiple biogeochemical factors. In conclusion, the novel in situ whole soil warming experiment gives insight for the first time into the response of subsoil microorganisms to warming and how subsoil organic carbon quality changes with warming-induced degradation. The results improve our understanding of subsoil carbon dynamics under global warming and show that subsoil organic carbon might be more vulnerable to decomposition under warming compared to topsoil organic carbon. Furthermore, complex plant and pyrogenic polymers were lost on the same order of magnitude as bulk soil organic carbon in subsoils. This finding improves our understanding on the long-term fate of compounds which are considered for carbon sequestration purposes. Finally, the thesis opens up exciting avenues for research on subsoil carbon dynamics under global change, concerning the long-term response of subsoils to warming, dynamics in subsoils of other ecosystems and interactions of warming with other global change drivers

Analyse des retombées économiques directes de la Balade des Divins à Sion

L’office du tourisme de Sion organise depuis 2009, la balade des Divins, une activité qui a pour but d’animer et de faire connaitre la ville. Aujourd’hui, après trois ans, le comité d’organisation aimerait connaitre les retombées économiques directes engendrées par cette manifestation. En effet, si cette activité est bénéfique en termes d’image et dynamise de manière certaine la ville, qu’en est-il au niveau économique ? Apporte-elle réellement une plus-value à l’économie locale ? A l’aide d’un questionnaire et de communications personnelles, les dépenses des participants ainsi que celles de l’entreprise ont été analysées et déterminées afin d’estimer l’impact direct. Souhaitant avoir une vision plus globale de l’événement et de son environnement, les aspects découlant de la manifestation telle que la satisfaction, la notoriété ou les impacts socio-culturels ont été également brièvement abordé. Ainsi, au terme de cette recherche, les résultats ont notamment démontré que si l’apport économique était faible, les retombées en termes de valeur promotionnelle et d’image étaient quant à eux positifs

How should a tourist organization optimize working with social Influencers?: case: Switzerland tourism north America

Tired of being bombarded with marketing messages, consumers have lost trust in brands. Paid advertisement is no longer effective and brands have to find new marketing practices to connect to consumers with more authenticity. Influencer marketing is an increasingly popular method in which a brand partners with key individuals who exert influence over an online community. Brands can thus tap into a network of trust. Influencer marketing is digital word-of-mouth: it is based on recommendations from someone consumers align with

Horndeski under the quantum loupe

With recent constraints on the propagation speed of gravitational waves, the class of scalar-tensor theories has significantly been reduced. We consider one of the surviving models still relevant for cosmology and investigate its radiative stability. The model contains operators with explicit breaking of the Galileon symmetry and we study whether they harm the re-organization of the effective field theory. Within the regime of validity we establish a non-renormalization theorem and show explicitly that the quantum corrections, to one-loop, do not detune the classical Lagrangian generating suppressed counterterms. This is striking since the non-renormalization theorem is established in the presence of a genuine Galileon symmetry breaking term.Comment: 23 pages, 4 figure

Gravitational wave memory beyond general relativity

Gravitational wave memory is a nonoscillatory correction to the gravitational wave strain predicted by general relativity, which has yet to be detected. Within general relativity, its dominant component, known as the null memory, can be understood as arising from the backreaction of the energy carried by gravitational waves, and therefore it corresponds to a direct manifestation of the nonlinearity of the theory. In this paper, we investigate the null-memory prediction in a broad class of modified gravity theories, with the aim of exploring potential lessons to be learned from future measurements of the memory effect. Based on Isaacson's approach to the leading-order field equations, we in particular compute the null memory for the most general scalar-vector-tensor theory with second-order equations of motion and vanishing field potentials. We find that the functional form of the null memory is only modified through the potential presence of additional radiative null energy sources in the theory. We subsequently generalize this result by proving a theorem that states that the simple structure of the tensor null-memory equation remains unaltered in any metric theory whose massless gravitational fields satisfy decoupled wave equations to first order in perturbation theory, which encompasses a large class of viable extensions to general relativity.Comment: 39 page

Unifying Ordinary and Null Memory

Based on a recently proposed reinterpretation of gravitational wave memory that builds up on the definition of gravitational waves pioneered by Isaacson, we provide a unifying framework to derive both ordinary and null memory from a single well-defined equation at leading order in the asymptotic expansion. This allows us to formulate a memory equation that is valid for any unbound asymptotic energy-flux that preserves local Lorentz invariance. Using Horndeski gravity as a concrete example metric theory with an additional potentially massive scalar degree of freedom in the gravitational sector, the general memory formula is put into practice by presenting the first account of the memory correction sourced by the emission of massive field waves. Throughout the work, physical degrees of freedom are identified by constructing manifestly gauge invariant perturbation variables within an SVT decomposition on top of the asymptotic Minkowski background, which will in particular prove useful in future studies of gravitational wave memory within vector tensor theories.Comment: 17 pages. Comments are welcom

L'Histoire du progrès: L’histoire nationale influence-t-elle sur la conception du progrès qu’ont les élèves de fin de scolarité obligatoire ? Comparaison entre la Suisse et la Russie

Ce mémoire est avant tout une comparaison de l’appréhension de la notion de progrès que peuvent avoir des élèves de fin de scolarité. Cette étude a été effectuée au cours d’une année scolaire, autant en Suisse qu’en Russie. Ces deux pays ont été choisis de manière opportune, vu l’histoire qu’ils ont développée en parallèle (idéologie capitaliste vs idéologie communiste). Le but étant de savoir si l’histoire du pays influence sur la conception qu’ont les élèves d’aujourd’hui de ce concept qu’est le progrès. Pour réaliser ce mémoire, autant des questionnaires identiques ont été passés dans les deux pays, que des focus group ont pu être réalisés. En outre, une séquence en histoire a été effectuée dans la classe de Suisse romande afin de faire mieux comprendre cette notion apparaissant comme trop abstraite pour les adolescents helvétiques. En effet, ces derniers indiquaient, de manière générale, que seul le progrès technologique était important et qu’il avait été notable au cours du XXe siècle, élément bien plus nuancé de la part des élèves russes, soulevant des problématiques diverses (telles que l’aspect social, culturelle ou cultuelle, lié aux infrastructures ou encore politique). Les résultats de cette recherche montre, dès lors, que plus que l’histoire nationale, c’est l’histoire récente du pays qui a un impact conséquent sur la manière qu’ont les adolescents d’élaborer cette pensée. Les élèves suisses romands ont de la peine à saisir le progrès, alors que cette notion apparaît comme beaucoup plus concrète pour leurs homologues russes. Ainsi, nous avons pu soulever de nombreux éléments intéressants lors de cette analyse. Par exemple, relevons l’évolution de l’adolescent qui permet d’avoir une pensée plus variée avec son développement intellectuel, et surtout l’histoire récente du pays portant une incidence notoire sur l’idée même du progrès. Nous déplorons enfin, le fait que nous n’ayons pas eu suffisamment de temps ni de moyens pour analyser l’intégralité des réponses reçues de la part des élèves, autant suisses romands, que russes