Fluid-membrane tethers: minimal surfaces and elastic boundary layers

Thin cylindrical tethers are common lipid bilayer membrane structures, arising in situations ranging from micromanipulation experiments on artificial vesicles to the dynamic structure of the Golgi apparatus. We study the shape and formation of a tether in terms of the classical soap-film problem, which is applied to the case of a membrane disk under tension subject to a point force. A tether forms from the elastic boundary layer near the point of application of the force, for sufficiently large displacement. Analytic results for various aspects of the membrane shape are given.Comment: 12 page

Low and High Energy Phenomenology of Quark-Lepton Complementarity Scenarios

We conduct a detailed analysis of the phenomenology of two predictive see-saw scenarios leading to Quark-Lepton Complementarity. In both cases we discuss the neutrino mixing observables and their correlations, neutrinoless double beta decay and lepton flavor violating decays such as mu -> e gamma. We also comment on leptogenesis. The first scenario is disfavored on the level of one to two standard deviations, in particular due to its prediction for U_{e3}. There can be resonant leptogenesis with quasi-degenerate heavy and light neutrinos, which would imply sizable cancellations in neutrinoless double beta decay. The decays mu -> e gamma and tau -> mu gamma are typically observable unless the SUSY masses approach the TeV scale. In the second scenario leptogenesis is impossible. It is however in perfect agreement with all oscillation data. The prediction for mu -> e gamma is in general too large, unless the SUSY masses are in the range of several TeV. In this case tau -> e gamma and tau -> mu gamma are unobservable.Comment: 32 pages, 9 figures. Discussion on leptogenesis changed due to inclusion of flavor effects. To appear in PR

Imaging the Earth's Interior: the Angular Distribution of Terrestrial Neutrinos

Decays of radionuclides throughout the Earth's interior produce geothermal heat, but also are a source of antineutrinos. The (angle-integrated) geoneutrino flux places an integral constraint on the terrestrial radionuclide distribution. In this paper, we calculate the angular distribution of geoneutrinos, which opens a window on the differential radionuclide distribution. We develop the general formalism for the neutrino angular distribution, and we present the inverse transformation which recovers the terrestrial radioisotope distribution given a measurement of the neutrino angular distribution. Thus, geoneutrinos not only allow a means to image the Earth's interior, but offering a direct measure of the radioactive Earth, both (1) revealing the Earth's inner structure as probed by radionuclides, and (2) allowing for a complete determination of the radioactive heat generation as a function of radius. We present the geoneutrino angular distribution for the favored Earth model which has been used to calculate geoneutrino flux. In this model the neutrino generation is dominated by decays in the Earth's mantle and crust; this leads to a very ``peripheral'' angular distribution, in which 2/3 of the neutrinos come from angles > 60 degrees away from the downward vertical. We note the possibility of that the Earth's core contains potassium; different geophysical predictions lead to strongly varying, and hence distinguishable, central intensities (< 30 degrees from the downward vertical). Other uncertainties in the models, and prospects for observation of the geoneutrino angular distribution, are briefly discussed. We conclude by urging the development and construction of antineutrino experiments with angular sensitivity. (Abstract abridged.)Comment: 25 pages, RevTeX, 7 figures. Comments welcom

Effective Area-Elasticity and Tension of Micro-manipulated Membranes

We evaluate the effective Hamiltonian governing, at the optically resolved scale, the elastic properties of micro-manipulated membranes. We identify floppy, entropic-tense and stretched-tense regimes, representing different behaviors of the effective area-elasticity of the membrane. The corresponding effective tension depends on the microscopic parameters (total area, bending rigidity) and on the optically visible area, which is controlled by the imposed external constraints. We successfully compare our predictions with recent data on micropipette experiments.Comment: To be published in Phys. Rev. Let

Elastic deformation of a fluid membrane upon colloid binding

When a colloidal particle adheres to a fluid membrane, it induces elastic deformations in the membrane which oppose its own binding. The structural and energetic aspects of this balance are theoretically studied within the framework of a Helfrich Hamiltonian. Based on the full nonlinear shape equations for the membrane profile, a line of continuous binding transitions and a second line of discontinuous envelopment transitions are found, which meet at an unusual triple point. The regime of low tension is studied analytically using a small gradient expansion, while in the limit of large tension scaling arguments are derived which quantify the asymptotic behavior of phase boundary, degree of wrapping, and energy barrier. The maturation of animal viruses by budding is discussed as a biological example of such colloid-membrane interaction events.Comment: 14 pages, 9 figures, REVTeX style, follow-up on cond-mat/021242

The see-saw mechanism: neutrino mixing, leptogenesis and lepton flavor violation

The see-saw mechanism to generate small neutrino masses is reviewed. After summarizing our current knowledge about the low energy neutrino mass matrix we consider reconstructing the see-saw mechanism. Low energy neutrino physics is not sufficient to reconstruct see-saw, a feature which we refer to as ``see-saw degeneracy''. Indirect tests of see-saw are leptogenesis and lepton flavor violation in supersymmetric scenarios, which together with neutrino mass and mixing define the framework of see-saw phenomenology. Several examples are given, both phenomenological and GUT-related. Variants of the see-saw mechanism like the type II or triplet see-saw are also discussed. In particular, we compare many general aspects regarding the dependence of LFV on low energy neutrino parameters in the extreme cases of a dominating conventional see-saw term or a dominating triplet term. For instance, the absence of mu -> e gamma or tau -> e gamma in the pure triplet case means that CP is conserved in neutrino oscillations. Scanning models, we also find that among the decays mu -> e gamma, tau -> e gamma and tau -> mu gamma the latter one has the largest branching ratio in (i) SO(10) type I see-saw models and in (ii) scenarios in which the triplet term dominates in the neutrino mass matrix.Comment: 26 pages, 7 figures. Expanded version of talk given at 10th Workshop In High Energy Physics Phenomenology (WHEPP 10), January 2008, Chennai, India. Typos corrected, comments and references adde

Membranes by the Numbers

Many of the most important processes in cells take place on and across membranes. With the rise of an impressive array of powerful quantitative methods for characterizing these membranes, it is an opportune time to reflect on the structure and function of membranes from the point of view of biological numeracy. To that end, in this article, I review the quantitative parameters that characterize the mechanical, electrical and transport properties of membranes and carry out a number of corresponding order of magnitude estimates that help us understand the values of those parameters.Comment: 27 pages, 12 figure

Cenozoic history of Antarctic glaciation and climate from onshore and offshore studies

The past three decades have seen a sustained and coordinated effort to refine the seismic stratigraphic framework of the Antarctic margin that has underpinned the development of numerous geological drilling expeditions from the continental shelf and beyond. Integration of these offshore drilling datasets covering the Cenozoic era with Antarctic inland datasets, provides important constraints that allow us to understand the role of Antarctic tectonics, the Southern Ocean biosphere, and Cenozoic ice sheet dynamics and ice sheet–ocean interactions on global climate as a whole. These constraints are critical for improving the accuracy and precision of future projections of Antarctic ice sheet behaviour and changes in Southern Ocean circulation. Many of the recent advances in this field can be attributed to the community-driven approach of the Scientific Committee on Antarctic Research (SCAR) Past Antarctic Ice Sheet Dynamics (PAIS) research programme and its two key subcommittees: Paleoclimate Records from the Antarctic Margin and Southern Ocean (PRAMSO) and Palaeotopographic-Palaeobathymetric Reconstructions. Since 2012, these two PAIS subcommittees provided the forum to initiate, promote, coordinate and study scientific research drilling around the Antarctic margin and the Southern Ocean. Here we review the seismic stratigraphic margin architecture, climatic and glacial history of the Antarctic continent following the break-up of Gondwanaland in the Cretaceous, with a focus on records obtained since the implementation of PRAMSO. We also provide a forward-looking approach for future drilling proposals in frontier locations critically relevant for assessing future Antarctic ice sheet, climatic and oceanic change.We thank many people who collaborated, by sharing data and ideas, on geoscience research projects under the umbrella of the highly successful Paleoclimate Records from the Antarctic Margin and Southern Ocean (PRAMSO) and Palaeotopographic-Palaeobathymetric Reconstructions subcommittees of the Scientific Committee on Antarctic Research (SCAR) Past Antarctic Ice Sheet scientific program. This synthesis, which reflects our views, would not have been possible without the efforts of these many investigators, most of whom continue their collaborative Antarctic studies, now under the successor SCAR INSTANT programme. Chris Sorlien is thanked for drafting Fig. 3.6. We thank John Anderson, Peter Barrett, Giuliano Brancolini and Alan Cooper for their useful comments and for their continuous dedication to the past Antarctic Ice Sheet evolution reconstructions. We thank Nigel Wardell, Frank Nitsche and Paolo Diviacco for maintaining the Seismic Data Library System and the National Antarctic funding agencies of many countries (Australia, China, Germany, Italy, Japan, Korea, New Zealand, Russia, Spain, the UK, the United States) for supporting geophysical and geological surveys essential for Paleotopographic and Paleobathymetric reconstructions. We thank the International Ocean Discovery Program (IODP) for its support of recent expeditions that arose out of PRAMSO discussions. R.M. was funded by the Royal Society Te Apārangi NZ Marsden Fund (grant 18-VUW-089). C.E. acknowledges funding by the Spanish Ministry of Economy, Industry and Competitivity (grants CTM2017-89711-C2-1/2-P), cofunded by the European Union through FEDER funds. L.D.S. and F.D. were funded by the Programma Nazionale delle Ricerche in Antartide (PNRA16_00016 project and PNRA 14_00119). R.Larter and C.D.H. were funded by the BAS Polar Science for Planet Earth Programme and NERC UK IODP grant NE/J006548/1. S.K. was supported by the KOPRI Grant (PE21050). L.P. was funded by the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 792773 WAMSISE. A.S. and S.G. were funded by NSF Office of Polar Programs (Grants OPP-1744970 (A.S.), -1143836 (A.S.), and -1143843 (S.G.). This is University of Texas Institute for Geophysics Contribution #3784. B.D. acknowledges funding from a Rutherford Foundation Postdoctoral Fellowship (RFT-VUW1804-PD). K.G. and G.K. were funded by AWI research programme Polar Regions and Coasts in the changing Earth System (PACES II) and the Sub-EIS-Obs programme by the Bundesanstalt für Geowissenschaften und Rohstoffe (BGR). RL, RM, TN acknowledge support from MBIE Antarctic Science Platform contract ANTA1801

Repressing Anarchy in Neutrino Mass Textures

The recent results that $\theta_{13}$ is relatively large, of the order of the previous upper bound, and the indications of a sizable deviation of $\theta_{23}$ from the maximal value are in agreement with the predictions of Anarchy in the lepton sector. The quark and charged lepton hierarchies can then be reproduced in a SU(5) GUT context by attributing non-vanishing $U(1)_{FN}$ charges, different for each family, only to the SU(5) tenplet states. The fact that the observed mass hierarchies are stronger for up quarks than for down quarks and charged leptons supports this idea. As discussed in the past, in the flexible context of $SU(5)\otimes U(1)_{FN}$, different patterns of charges can be adopted going from Anarchy to various types of hierarchy. We revisit this approach by also considering new models and we compare all versions to the present data. As a result we confirm that, by relaxing the extreme ansatz of equal $U(1)_{FN}$ charges for all SU(5) pentaplets and singlets, better agreement with the data than for Anarchy is obtained without increasing the model complexity. We also present the distributions obtained in the different models for the Dirac CP-violating phase. Finally we discuss the relative merits of these simple models.Comment: v1: 12 pages, 3 figures; v2: 13 pages, 3 figures, text improved, matches version accepted for publication; v3: submitted to add an acknowledgment to a networ