Soliton Lattices in the Incommensurate Spin-Peierls Phase: Local Distortions and Magnetizations

It is shown that nonadiabatic fluctuations of the soliton lattice in the spin-Peierls system CuGeO_3 lead to an important reduction of the NMR line widths. These fluctuations are the zero-point motion of the massless phasonic excitations. Furthermore, we show that the discrepancy of X-ray and NMR soliton widths can be understood as the difference between a distortive and a magnetic width. Their ratio is controlled by the frustration of the spin system. By this work, theoretical and experimental results can be reconciled in two important points.Comment: 9 pages, 5 figures included, Revtex submitted to Physical Review

Middle-Upper Triassic stratigraphy and structure in the Alt Palància region (eastern Iberian Chain): A multidisciplinary approach

The present study provides new data of the Middle-Upper Triassic successions and their deformation in the eastern Iberian Chain, where contractional tectonics during the Cenozoic disrupted this Mediterranean type of Triassic rocks. The succession, divided into three Muschelkalk units, was studied in the Alt Palància area. In this area, both the lower and upper Muschelkalk consist of two main types of sub-units, those made up of carbonate and those of carbonate-marl alternation. The marked similarity observed between the evaporite units of the middle Muschelkalk and the Keuper humpers their unambiguous discrimination in the field. The integration of geological mapping, stratigraphic logging, palynological dating and gypsum isotope analysis carried out provided that: i) a change in the structural style, facies, and depositional thickness occurs across a SW to NE transect at both sides of the Espina-Espadà Fault, providing evidence for the extensional activity of this major structure; ii) palynological data assign Anisian age to the Röt facies and the lower and the middle Muschelkalk units, and Ladinian to the upper Muschelkalk unit; iii) the δ34SCDT and δ18OSMOW values of gypsum reveal as a useful proxy to discriminate between the middle Muschelkalk (δ34S: 15.6 to 17.8‰) and the Keuper (δ34S: 14 to 15.5‰) units; and iv) the isotopic signature also helps to identify clayey-marly gypsiferous outcrops made up of the two evaporite facies due to tectonic juxtaposition. These results confirm the Mediterranean type of Triassic rocks for the entire Alt Palància and other areas to the NE. This multidisciplinary approach reveals as a robust methodology to study Triassic basins in Iberia and to other geological domains where the carbonate-evaporite successions have been greatly disrupted by tectonism

Middle-Upper Triassic stratigraphy and structure in the Alt Palància region (eastern Iberian Chain): A multidisciplinary approach

The present study provides new data of the Middle-Upper Triassic successions and their deformation in the eastern Iberian Chain, where contractional tectonics during the Cenozoic disrupted this Mediterranean type of Triassic rocks. The succession, divided into three Muschelkalk units, was studied in the Alt Palància area. In this area, both the lower and upper Muschelkalk consist of two main types of sub-units, those made up of carbonate and those of carbonate-marl alternation. The marked similarity observed between the evaporite units of the middle Muschelkalk and the Keuper humpers their unambiguous discrimination in the field. The integration of geological mapping, stratigraphic logging, palynological dating and gypsum isotope analysis carried out provided that: i) a change in the structural style, facies, and depositional thickness occurs across a SW to NE transect at both sides of the Espina-Espadà Fault, providing evidence for the extensional activity of this major structure; ii) palynological data assign Anisian age to the Röt facies and the lower and the middle Muschelkalk units, and Ladinian to the upper Muschelkalk unit; iii) the δ34SCDT and δ18OSMOW values of gypsum reveal as a useful proxy to discriminate between the middle Muschelkalk (δ34S: 15.6 to 17.8‰) and the Keuper (δ34S: 14 to 15.5‰) units; and iv) the isotopic signature also helps to identify clayey-marly gypsiferous outcrops made up of the two evaporite facies due to tectonic juxtaposition. These results confirm the Mediterranean type of Triassic rocks for the entire Alt Palància and other areas to the NE. This multidisciplinary approach reveals as a robust methodology to study Triassic basins in Iberia and to other geological domains where the carbonate-evaporite successions have been greatly disrupted by tectonism

Gamma ray burst studies with THESEUS

International audienceGamma-ray Bursts (GRBs) are the most powerful transients in the Universe, over–shining for a few seconds all other γ-ray sky sources. Their emission is produced within narrowly collimated relativistic jets launched after the core–collapse of massive stars or the merger of compact binaries. THESEUS will open a new window for the use of GRBs as cosmological tools by securing a statistically significant sample of high-z GRBs, as well as by providing a large number of GRBs at low–intermediate redshifts extending the current samples to low luminosities. The wide energy band and unprecedented sensitivity of the Soft X-ray Imager (SXI) and X-Gamma rays Imaging Spectrometer (XGIS) instruments provide us a new route to unveil the nature of the prompt emission. For the first time, a full characterisation of the prompt emission spectrum from 0.3 keV to 10 MeV with unprecedented large count statistics will be possible revealing the signatures of synchrotron emission. SXI spectra, extending down to 0.3 keV, will constrain the local metal absorption and, for the brightest events, the progenitors’ ejecta composition. Investigation of the nature of the internal energy dissipation mechanisms will be obtained through the systematic study with XGIS of the sub-second variability unexplored so far over such a wide energy range. THESEUS will follow the spectral evolution of the prompt emission down to the soft X–ray band during the early steep decay and through the plateau phase with the unique ability of extending above 10 keV the spectral study of these early afterglow emission phases