Derivative couplings in gravitational production in the early universe

Gravitational particle production in the early universe is due to the coupling of matter fields to curvature. This coupling may include derivative terms that modify the kinetic term. The most general first order action contains derivative couplings to the curvature scalar and to the traceless Ricci tensor, which can be dominant in the case of (pseudo-)Nambu-Goldstone bosons or disformal scalars, such as branons. In the presence of these derivative couplings, the density of produced particles for the adiabatic regime in the de Sitter phase (which mimics inflation) is constant in time and decays with the inverse effective mass (which in turn depends on the coupling to the curvature scalar). In the reheating phase following inflation, the presence of derivative couplings to the background curvature modifies in a nontrivial way the gravitational production even in the perturbative regime. We also show that the two couplings -- to the curvature scalar and to the traceless Ricci tensor -- are drastically different, specially for large masses. In this regime, the production becomes highly sensitive to the former coupling while it becomes independent of the latter.Comment: 24 pages, 6 figure

Noble gas variation during partial crustal melting and magma ascent processes

Noble gas isotopes, although present in trace amounts, are generally more reliable and less ambiguous recorders of their source than the major volatile species. In volcanic settings in particular, this advantage derives from their chemical inertness, as noble gas isotopic and elemental fractionations are strongly coupled to their source and modified only by physical processes during magma ascent and eruption. The Neogene volcano El Hoyazo (Betic Cordillera, SE Spain) is a highly favourable natural laboratory to study the links between partial crustal melting processes occurring at depth and the eruptive products at the surface, because partially melted crustal xenoliths are preserved in silicic lavas. Comparing the noble gas isotopic compositions of xenoliths and lavas has the potential to yield new insights into volatile behaviour during melting processes at inaccessible depths in the crust. At El Hoyazo, noble gases trapped in lava glasses, and the fluid/melt inclusions within xeno- and phenocrysts, provide novel information on: (i) their response to the crustal melting process including mechanisms such as magma mixing (and crustal assimilation) of two endmembers: i.e. the extracted felsic melt from the country metapelitic crust, and the basic-intermediate magma from the underplating in the region. The results reveal significant modification of magmatic noble gases by the interaction with the partially melted crust; (ii) noble gas variations during degassing and magma ascent, showing higher atmospheric influence in the lava samples from shallower depths than in the deeper lavas and minerals; and (iii) higher magmatic influence in crystals of garnet from deeper lava than in both shallower crystals of amphibole, and garnet crystals within the crustal xenoliths. In addition, we find that noble gases in melt inclusions are also likely accumulating in their shrinkage bubbles, and not only remaining dissolved in the melt.Postprint3,51

YASA: yet another time series segmentation algorithm for anomaly detection in big data problems

Time series patterns analysis had recently attracted the attention of the research community for real-world applications. Petroleum industry is one of the application contexts where these problems are present, for instance for anomaly detection. Offshore petroleum platforms rely on heavy turbomachines for its extraction, pumping and generation operations. Frequently, these machines are intensively monitored by hundreds of sensors each, which send measurements with a high frequency to a concentration hub. Handling these data calls for a holistic approach, as sensor data is frequently noisy, unreliable, inconsistent with a priori problem axioms, and of a massive amount. For the anomalies detection problems in turbomachinery, it is essential to segment the dataset available in order to automatically discover the operational regime of the machine in the recent past. In this paper we propose a novel time series segmentation algorithm adaptable to big data problems and that is capable of handling the high volume of data involved in problem contexts. As part of the paper we describe our proposal, analyzing its computational complexity. We also perform empirical studies comparing our algorithm with similar approaches when applied to benchmark problems and a real-life application related to oil platform turbomachinery anomaly detection

Author Correction: Noble gas isotopes reveal degassing-derived eruptions at Deception Island (Antarctica): implications for the current high levels of volcanic activity

Peer reviewe

Noble gas isotopes reveal degassing-derived eruptions at Deception Island (Antarctica): implications for the current high levels of volcanic activity

Deception Island is one of the most active volcanoes in Antarctica with more than twenty explosive eruptions in the past two centuries. Any future volcanic eruption(s) is a serious concern for scientists and tourists, will be detrimental to marine ecosystems and could have an impact to global oceanographic processes. Currently, it is not possible to carry-out low and high frequency volcanic gas monitoring at Deception Island because of the arduous climatic conditions and its remote location. Helium, neon and argon isotopes measured in olivine samples of the main eruptive events (pre-, syn- and post caldera) offer insights into the processes governing its volcanic history. Our results show that: (i) ascending primitive magmas outgassed volatiles with a MORB-like helium isotopic signature (3He/4He ratio); and (ii) variations in the He isotope ratio, as well as intensive degassing evidenced by fractionated 4He/40Ar* values, occurred before the beginning of the main eruptive episodes. Our results show how the pre-eruptive noble gas signals of volcanic activity is an important step toward a better understanding of the magmatic dynamics and has the potential to improve eruption forecasting.This research was supported by the Spanish Government (MICINN) projects: RECALDEC (CTM2009-05919-E/ANT), PEVOLDEC (CTM2011-13578-E/ANT), POSVOLDEC (CTM2016-79617-P)(AEI/FEDER, UE), VOLGASDEC (PGC2018-095693-B-I00)(AEI/FEDER, UE), HYDROCAL (PID2020-114876GB-I00)(MCIN/AEI/10.13039/501100011033), EruptING (PID2021-127189OB-I00) (MCIN/AEI/10.13039/501100011033), and Programa Propio’s project (Universidad de Salamanca-2019 modalidad 1B). A.A-V also thanks the JSPS invitation fellowship (S18113) at the University of Tokyo. A.P.S is grateful for his PhD grant “Programa Propio III Universidad de Salamanca-2021 cofounded by Banco de Santander”.Peer reviewe