Dark-matter dynamical friction versus gravitational-wave emission in the evolution of compact-star binaries

The measured orbital period decay of compact-star binaries, with characteristic orbital periods $\sim 0.1$~days, is explained with very high precision by the gravitational wave (GW) emission of an inspiraling binary in vacuum. However, the binary gravitational binding energy is also affected by an usually neglected phenomenon, namely the dark matter dynamical friction (DMDF) produced by the interaction of the binary components with their respective DM gravitational wakes. The entity of this effect depends on the orbital period and on the local value of the DM density, hence on the position of the binary in the Galaxy. We evaluate the DMDF produced by three different DM profiles: the Navarro-Frenk-White (NFW), the non-singular-isothermal-sphere (NSIS) and the Ruffini-Arg\"uelles-Rueda (RAR) profile based on self-gravitating keV fermions. We first show that indeed, due to their Galactic position, the GW emission dominates over the DMDF in the NS-NS, NS-WD and WD-WD binaries for which measurements of the orbital decay exist. Then, we evaluate the conditions under which the effect of DMDF on the binary evolution becomes comparable to, or overcomes, the one of the GW emission. We find that, for instance for $1.3$--$0.2$ $M_\odot$ NS-WD, $1.3$--$1.3$~$M_\odot$ NS-NS, and $0.25$--$0.50$~$M_\odot$ WD-WD, located at 0.1~kpc, this occurs at orbital periods around 20--30 days in a NFW profile while, in a RAR profile, it occurs at about 100 days. For closer distances to the Galactic center, the DMDF effect increases and the above critical orbital periods become interestingly shorter. Finally, we also analyze the system parameters for which DMDF leads to an orbital widening instead of orbital decay. All the above imply that a direct/indirect observational verification of this effect in compact-star binaries might put strong constraints on the nature of DM and its Galactic distribution.Comment: 15 pages, 12 figures, 2 tables, accepted for publication in Phys. Rev. D, 201

Heuristic Classification of Physical Theories based on Quantum Correlations

Taking quantum formalism as a point of reference and connection, we explore the various possibilities that arise in the construction of physical theories. Analyzing the distinct physical phenomena that each of them may describe, we introduce the different types of hidden variables theories that correspond to these physical phenomena. A hierarchical classification of the offered theories, based on the degree of correlation between dichotomic observables in bipartite systems, as quantified by a Bell type inequality, is finally proposed.Comment: 13 pages, 2 figure

Interactive effects of solar UV radiation and ammonium on the biomass andnutritional compound production in tank cultivated Hydropuntia corne (Rhodophyta)

Figueroa et al. (2016) Acta Aquaculture 16, 331-332Introduction Hydropuntia cornea is a red alga species cultivated in tanks under nitrogen enrichment with high biomass production and content of high value bioactive compounds (Figueroa et al., 2012; Robledo et al, 2014). In this study, the combined effects (2 × 2 factorial design) of solar radiation (in door (I), green house cutting off the UV radiation and out-door (O) with UV radiation) and nitrogen (ammonium) under high (HN) and low (LN) levels on biomass production (g DW m-2 d-1), biofiltration as Nitrogen uptake efficiency (NUE, %) and Nitrogen uptake rate (NUR, mmol N m-2 h-1), photosynthetic activity as maximal electron transport rate (ETRmax), starch content and antioxidant activity were analyzed in H.cornea grown in tanks for 35 days in the above mentioned conditions. Material and methods The red seaweed Hydropuntia cornea was cultivated in cylindrical tanks of 90 L (0.17 m2 superficial area) with open flow-through N and P-enrichment (5 NH4Cl: 1 KHPO4, in a concentration ranges between 50 - 250 µM). Seaweed density assayed in tanks was 9 g FW L-1. Turnover rates were 64 and 6.4 vol d-1 in high and low flow rate, respectively. Photosynthetic activity was measured by using in vivo chlorophyll a fluorescence associated to photosystem II i.e. Electron transport rate (ETR) expressed as μmol electrons m-2 s-1. Starch (%) was determined according to anthrone method (Brooks et al. 1986) and antioxidant activity was evaluated following ABTS method (Ree et al., 1999) and expressed as Trolox equivalent (μM TEAC g-1 DW). Results Maximal photosynthetic production (ETRmax) increased throughout the culture time. (Fig. 1.A). After 35 d culture, ETRmax was higher under HN than that under LN both under in door and out door conditions (Fig.1A). However, biomass production expressed as g DW m-2 d-1 decreased throughout the experimental time (Fig 1.B). After 35d culture the highest biomass production was reached under HN-O and the lowest under LN-O although the differences were not so high (Fig.1B). The maximal efficiency of N assimilation (NUE %) was greater under LN (98%) than that under HN treatment (72%). NUE decreased throughout the time although after 35 d a clear increase was observed (Table 1). In contrast, the maximal nitrogen uptake rate (NUR) was higher under HN (45.5 mmol N m-2 h-1) than that under LN (25.8 mmol N m-2 h-1). The highest values of both NUE and NUR were obtained under solar radiation (outdoor treatments). Starch ranged from 25.1% (LN-I, 21 d) to 49.6 % (LN-O, 28 d) whereas the highest antioxidant activity was reached under LN-O after 21 d culture (68.5 μM TEAC g-1 DW). After 35d the highest level was again under LN-O (65.2 μM TEAC g-1 DW) followed by HN-O treatment (57.3 μM TEAC g-1 DW).Discussion and conclusions Ammonium supply, simulating fishpond effluents, and full solar irradiation (presence of UV radiation) have a positive effect on photosynthetic rate as ETRmax. The decrease in biomass production in spite of the increase of photosynthetic activity and nitrogen uptake rate is explained because the algae through the time could inverse more energy for the accumulation of metabolites (starch and antioxidant compounds) that that for growth. In any case the highest accumulation of starch and antioxidant activity were observed in the treatments associated to the greatest stress conditions i.e LN and outdoor culture due to UVR can negatively affect biological processes related to growth. As expected, under HN supply NUE was lower than that under LN but NUR was the reverse. H. cornea grown in simulated fishpond effluents displays a high biofiltration rate of inorganic N and accumulates commercially N compounds, as the photoprotector-antioxidant substances, mycosporine-like aminoacids (Figueroa et al., 2012) and C-compounds for nutritional uses or bioethanol production. In this study, the antioxidant activity was much higher than that reported in other seaweeds (Matanjun et al., 2008). H. cornea can be cultured and used to remove nutrient-rich fishpond effluents from aquaculture industries and besides, this biomass provides compounds of high added value for the biotechnology industry. References Brooks, J.R., Griffin, V.K., Kattan, M.W. 1986.A modified method for total carbohydrate analysisof glucose syrups, maltodextrins and other starch hydrolysis products. Cereal Chem 63:465-466. Figueroa, F. L., Korbee, N., Abdala, R., Jerez, C. G., López-de la Torre, M., Güenaga, L., Gómez-Pinchetti, J. L. 2012. Biofiltration of fishpond effluents and accumulation of N-compounds (phycobiliproteins and mycosporine-like amino acids) versus C-compounds (polysaccharides) in Hydropuntia cornea (Rhodophyta). Marine Pollution Bulletin, 64(2), 310-318. Matanjun, P., Mohamed, S., Mustapha, N.M., Ming, C.H. 2008. Antioxidant activities and phenolics content of eight species of seaweeds from north Borneo. J Appl Phycol 20:367–373. Re, R., Pellegrini, N., Proteggente, A., Pannala, A.,Yang,M., Rice-Evans, C. 1999. Antioxidant activity applying an improved ABTS radical cation decolorization assay. Free Radic Biol Med 26:1231–1237. Robledo, D., Navarro‐Angulo, L., Valdes Lozano, D., Freile‐Pelegrín, Y. 2014. Nutrient removal efficiency of Hydropuntia cornea in an integrated closed recirculation system with pink shrimp Farfantepenaeus brasiliensis. Aquaculture Research, 45(10), 1648-1658Universidad de Málaga.Campus de Excelencia Internacional Andalucia Tech

Plasmonics in topological insulators: Spin-charge separation, the influence of the inversion layer, and phonon-plasmon coupling

We demonstrate via three examples that topological insulators (TI) offer a new platform for plasmonics. First, we show that the collective excitations of a thin slab of a TI display spin-charge separation. This gives rise to purely charge-like optical and purely spin-like acoustic plasmons, respectively. Second, we argue that the depletion layer mixes Dirac and Schr\"odinger electrons which can lead to novel features such as high modulation depths and interband plasmons. The analysis is based on an extension of the usual formula for optical plasmons that depends on the slab width and on the dielectric constant of the TI. Third, we discuss the coupling of the TI surface phonons to the plasmons and find strong hybridisation especially for samples with large slab widths.Comment: 37 pages, 7 figure

Spin-charge separation of plasmonic excitations in thin topological insulators

We discuss plasmonic excitations in a thin slab of a topological insulators. In the limit of no hybridization of the surface states and same electronic density of the two layers, the electrostatic coupling between the top and bottom layers leads to optical and acoustic plasmons which are purely charge and spin collective oscillations. We then argue that a recent experiment on the plasmonic excitations of Bi2Se3 [Di Pietro et al, Nat. Nanotechnol. 8, 556 (2013)] must be explained by including the charge response of the two-dimensional electron gas of the depletion layer underneath the two surfaces. We also present an analytic formula to fit their data.Comment: 7 pages, 5 figure