RESIK and RHESSI observations of the 20 September 2002 flare

Soft X-ray spectra 3.33 A - 6.15 A from the RESIK instrument on CORONAS-F constitute a unique database for the study of the physical conditions of solar flare plasmas, enabling the calculation of differential emission measures. The two RESIK channels for the shortest wavelengths overlap with the lower end of RHESSI spectral energy range, which is located around 3 keV, making it possible to compare both data sets. We aim to compare observations from RESIK and RHESSI spectrometers and cross-correlate these instruments. Observations are compared with synthetic spectra calculated based on the results of one-dimensional hydrodynamical (1D-HD) modelling. The analysis was performed for the flare on 20 September 2002. We estimated the geometry of the flaring loop, necessary for 1D-HD modelling, based on images from RHESSI and SOHO/EIT. The distribution of non-thermal electrons (NTEs) was determined from RHESSI spectra. The 1D-HD model assumes that non-thermal electrons with a power-law spectrum were injected at the apex of the flaring loop. The NTEs then heat and evaporate the chromosphere, filling the loop with hot and dense plasma radiating in soft X-rays. The total energy of electrons was constrained by comparing observed and calculated fluxes from GOES 1 - 8 A data. We determined the temperature and density at every point of the flaring loop throughout the evolution of the flare, calculating the resulting X-ray spectra. The synthetic spectra calculated based on the results of hydrodynamic modelling for the 20 September 2002 flare are consistent within a factor of two with the observed RESIK spectra during most of the duration of the flare. This discrepancy factor is probably related to the uncertainty on the cross-calibration between RESIK and RHESSI instruments

Universal class of type-IIB flux vacua with analytic mass spectrum

We report on a new class of flux vacua generically present in Calabi-Yau compactifications of type-IIB string theory. At these vacua, the mass spectrum of the complete axiodilaton/complex structure sector is given, to leading order in a' and g(s), by a simple analytic formula independent of the choice of Calabi-Yau. We provide a method to find these vacua and construct an ensemble of 17,054 solutions for the Calabi-Yau hypersurface WP[1,1,1,6,9]4, where the masses of the axiodilaton and the 272 complex structure fields can be explicitly computed.This work is supported by the Spanish Ministry MCIU/AEI/FEDER Grant No. PGC2018-094626-B-C21, the Basque Government Grant No. IT-979-16, and the Basque Foundation for Science (IKERBASQUE). K. S. is supported by the Czech science foundation GACR Grant No. 19-01850S. M. A. U. is also supported by the University of the Basque Country Grant No. PIF17/74. For the numerical work, we used the computing infrastructure of the ARINA cluster at the University of the Basque Country (UPV/EHU)

Towards a Complete Mass Spectrum of Type-IIB Flux Vacua at Large Complex Structure

The large number of moduli fields arising in a generic string theory compactification makes a complete computation of the low energy effective theory infeasible. A common strategy to solve this problem is to consider Calabi-Yau manifolds with discrete symmetries, which effectively reduce the number of moduli and make the computation of the truncated Effective Field Theory possible. In this approach, however, the couplings (e.g., the masses) of the truncated fields are left undetermined. In the present paper we discuss the tree-level mass spectrum of type-IIB flux compactifications at Large Complex Structure, focusing on models with a reduced one-dimensional complex structure sector. We compute the tree-level spectrum for the dilaton and complex structure moduli, including the truncated fields, which can be expressed entirely in terms of the known couplings of the reduced theory. We show that the masses of this set of fields are naturally heavy at vacua consistent with the KKLT construction, and we discuss other phenomenologically interesting scenarios where the spectrum involves fields much lighter than the gravitino. We also derive the probability distribution for the masses on the ensemble of flux vacua, and show that it exhibits universal features independent of the details of the compactification. We check our results on a large sample of flux vacua constructed in an orientifold of the Calabi-Yau WP[1,1,1,1,4]4. Finally, we also discuss the conditions under which the spectrum derived here could arise in more general compactifications

Correlations of spin splitting and orbital fluctuations due to 1/f charge noise in the Si/SiGe quantum dot

Theoretical Physic