Noble Gases Deliver Cool Dates from Hot Rocks

Heat transfer in the solid Earth drives processes that modify temperatures, leaving behind a clear signature that we can measure using noble gas thermochronology. This allows us to record the thermal histories of rocks and obtain the timing, rate, and magnitude of phenomena such as erosion, deformation, and fluid flow. This is done by measuring the net balance between the accumulation of noble gas atoms from radioactive decay and their loss by temperature-activated diffusion in mineral grains. Together with knowledge about noble gas diffusion in common minerals, we can then use inverse models of this accumulation–diffusion balance to recover thermal histories. This approach is now a mainstream method by which to study geodynamics and Earth evolution.

Thickness dependent transition from the 1T′ to Weyl semimetal phase in ultrathin MoTe2: electrical transport, noise and Raman studies

The resistivity of the semiconducting ultra-thin 1T′-MoTe2 shows a clear signature of temperature induced transition to Weyl semimetallic Td phase. Resistivity upturn at low temperature (∼20 K) confirms electron–electron interaction physics at the Weyl nodes.

β Pictoris: observations of the Ca ii H&K absorptions in 1997 and 1998

ABSTRACT We present spectroscopy with resolution R ∼ 33 000 of the circumstellar Ca ii H&K absorptions in the star β Pictoris during 1997 and 1998. From 1997 April onwards, both lines were observed simultaneously. A total of 688 spectra were obtained over 95 nights in order to characterize the lines’ behaviour. Near-continuous Falling Evaporating Body (FEB) variable absorption activity was seen, including additional strong, blueshifted features besides the one on 1997 June 19–20 already reported by others. Temporal coverage is more even than in the HARPS spectra from 2004–11 that have been analysed for FEB orbital parameters via a model of FEB evaporation. Our observations likely encompass the 1997–98 Hill-sphere transit by β Pic b, but we have found no clear signature of transiting material. Lower velocity FEB absorptions tend to be deeper, narrower and longer lived, in confirmation of earlier studies. The ratio of line strengths for one absorption on 1998 November 27 is evocative of the variations expected for a single FEB making a transit perpendicular to the stellar rotation axis. Analysis with the evaporation model produces similar distributions of orbital parameters to those obtained from the HARPS observations, but when the derived orbital parameters are fed into a model based solely on gravitational dynamics of point masses, the predicted FEB accelerations do not agree with observed values. More sophisticated modelling is called for. There is no convincing intrinsic variation in the central circumstellar absorption such as might be expected if an H i ring is responsible for the confinement of circumstellar Ca+ ions. Our observations are available electronically for further analysis by others.

Geometric order parameters derived from the Voronoi tessellation show signatures of the jamming transition

Order parameters derived from the Voronoi tesselation show a clear signature of the jamming transition with power law scaling.

DD fusion from a polarized HD target

Recently, we have proposed an experiment to test the persistence of the polarization in a fusion process (D+D→3He+n), using a powerful laser hitting a polarized HD target. The purpose of the present contribution is to examine in more detail the experimental constraints, to move from a principle proposal to a doable experiment. Some of the difficulties are as follows: Production of a windowless cryogenic HD target and target cryostat vacuum breakdown, identification of thermal fusion or accelerated deuterons, inducing nuclear reactions, and finally, a clear signature of the polarization persistence of the fused deuterons must be found. Those points will be reviewed and discussed in the scope of the new results presented at this conference.

Local group analogues – searching for the satellites of the nearest massive galaxies

We have performed a search for faint companions around the nearest massive galaxies. We see a clear signature of clustering of faint objects, both in projected separation and in velocity offset. The inferred satellite luminosity functions confirm that the abundance of faint satellites seen in the Local Group is typical of other nearby systems.

Elementary radiation patterns in pulsar profiles

Highly symmetric double features observed in averaged pulsar profiles can be interpreted as the imprint of microscopic radiation beam characteristic of radiative mechanism operating in pulsar magnetosphere. The data put strong constraints on the possible radiation patterns, excluding entire classes of mechanisms, such as those based on parallel acceleration, or those that have complicated beams. Instead, several properties of double features (such as their symmetry, depth, shape, merging rate, large polarisation degree, and the association with bifurcated emission components) are consistent with the extraordinary-mode part of the curvature radiation beam. This shows that double notches are a clear signature of the curvature radiation process. We show that even with the emission process fixed, detailed modelling of double features remains a rather sophisticated and demanding task.

CONFORMAL PHASE TRANSITION IN QCD LIKE THEORIES AND BEYOND

The dynamics with an infrared stable fixed point in the conformal window in QCD like theories with a relatively large number of fermion flavors is reviewed. The emphasis is on the description of a clear signature for the conformal window, which in particular can be useful for lattice computer simulations of these gauge theories.