Aspects of chiral symmetry in QCD at T = 128 MeV

We investigate several aspects of chiral symmetry in QCD at a temperature of T=128 MeV. The study is based on a 24×963 lattice-QCD ensemble with O(a)-improved Wilson quarks and physical up, down and strange quark masses. The pion quasiparticle turns out to be significantly lighter than the zero-temperature pion mass, even though the corresponding static correlation length is shorter. We perform a quantitative comparison of our findings to predictions of chiral perturbation theory. Among several order parameters for chiral symmetry restoration, we compute the difference of the vector- and axial-vector time-dependent correlators and find it to be reduced by a factor ∼2/3 as compared to its vacuum counterpart

Photon emissivity of the quark-gluon plasma: a lattice QCD analysis of the transverse channel

We present results for the thermal photon emissivity of the quark-gluon plasma derived from spatially transverse vector correlators computed in lattice QCD at a temperature of 250 MeV. The analysis of the spectral functions, performed at fixed spatial momentum, is based on continuum-extrapolated correlators obtained with two flavours of dynamical Wilson fermions. We compare the next-to-leading order perturbative QCD correlators, as well as the ${\cal N}=4$ supersymmetric Yang-Mills correlators at infinite coupling, to the correlators from lattice QCD and find them to lie within $\sim10\%$ of each other. We then refine the comparison, performing it at the level of filtered spectral functions obtained model-independently via the Backus-Gilbert method. Motivated by these studies, for frequencies $\omega\lesssim2.5\,$GeV we use fit ans\"atze to the spectral functions that perform well when applied to mock data generated from the NLO QCD or from the strongly-coupled SYM spectral functions, while the high-frequency part, $\omega\gtrsim 2.5\,$GeV, is matched to NLO QCD. We compare our results for the photon emissivity to our previous analysis of a different vector channel at the same temperature. We obtain the most stringent constraint at photon momenta around $k\simeq0.8\,$GeV, for which we find a differential photon emission rate per unit volume of $d\Gamma_\gamma/d^3k = (\alpha_{\rm em}/(\exp(k/T)-1))\times (2.2 \pm 0.8 ) \times 10^{-3}\,{\rm GeV}$.Comment: 26 pages, 13 figures, 1 tabl

Estimation of the photon production rate using imaginary momentum correlators

The thermal photon emission rate is determined by the spatially transverse, in-medium spectral function of the electromagnetic current. Accessing the spectral function using Euclidean data is, however, a challenging problem due to the ill-posed nature of inverting the Laplace transform. In this contribution, we present the first results on implementing the proposal of directly computing the analytic continuation of the retarded correlator at fixed, vanishing virtuality of the photon via the calculation of the appropriate Euclidean correlator at imaginary spatial momentum. We employ two dynamical O(a)-improved Wilson fermions at a temperature of 250 MeV.Comment: 9 pages, 7 figures, contribution to the 39th International Symposium on Lattice Field Theory (LATTICE2022

Malayaite Ceramic Pigments: a Combined Optical Spectroscopy and Neutron/X-ray Diffraction Study

Ceramic pigments based on the Cr-doped malayaite structure were synthesized by solid state reaction and characterized by optical spectroscopy and combined X-ray and neutron powder diffraction in order to elucidate the still unclear chromium substitution mechanisms. The results show that coloration is actually due to simultaneous occurrence of Cr4+ and Cr3+ ions in the crystal lattice. Spectroscopy data confirm that Cr4+ is replacing Sn4+ in the octahedral site and, in minor amount, Si4+ in the tetrahedral site. In addition, neutron powder diffraction data suggest that Cr3+ substitution for octahedral Sn4+ is charge balanced by formation of oxygen vacancies with no preference over the different oxygen sites. Upon incorporation of Cr ion, the SnO6 octahedra exhibit an off-centre displacement of central cation which in turn induces a rearrangement of both the octahedral and tetrahedral coordination shells

Functionalization of Indium Oxide for Empowered Detection of CO2 over an Extra-Wide Range of Concentrations

Carbon capture, storage, and utilization have becomefamiliar termswhen discussing climate change mitigation actions. Such endeavorsdemand the availability of smart and inexpensive devices for CO2 monitoring. To date, CO2 detection relies on opticalproperties and there is a lack of devices based on solid-state gassensors, which can be miniaturized and easily made compatible withInternet of Things platforms. With this purpose, we present an innovativesemiconductor as a functional material for CO2 detection.A nanostructured In2O3 film, functionalizedby Na, proves to enhance the surface reactivity of pristine oxideand promote the chemisorption of even rather an inert molecule asCO(2). An advanced operando equipment basedon surface-sensitive diffuse infrared Fourier transform is used toinvestigate its improved surface reactivity. The role of sodium isto increase the concentration of active sites such as oxygen vacanciesand, in turn, to strengthen CO2 adsorption and reactionat the surface. It results in a change in film conductivity, i.e.,in transduction of a concentration of CO2. The films exhibitexcellent sensitivity and selectivity to CO2 over an extra-widerange of concentrations (250-5000 ppm), which covers most indoorand outdoor applications due to the marginal influence by environmentalhumidity

On-farm seed priming interventions in agronomic crops

Priming techniques are gaining importance in agriculture with the increase in environmental stresses. Resource-poor farmers are in urgent need of such techniques as they are simple, economical, and value-added intervention associated with low-risk bearing factors. Seed enhancement methods are key to improve seed performance and achieve a good stand establishment. Worldwide beneficial effects of priming are recorded. But these technologies have still not reached most farmers. This review highlights the importance of on-farm priming strategies in modern crop production system to yield better productivity and obtain higher economic returns. Stimulation of the pre-germination metabolic changes by priming is necessary to overcome the environmental challenges that a plant can encounter. Thus, the study also focuses on mechanisms associated with priming-induced stress tolerance of crops. Various safe practical methods of seed priming can be easily adopted by the farming community to alleviate the levels of different stresses which can hamper productivity. Simultaneously they can produce good quality seeds and use them further for the next crop cycle cutting the costs of seed purchase.</p

Polytypism of AlPO4•2H2O variscite

Variscite (orthorhombic), a hydrated aluminophosphate with formula Al(PO4)•2H2O, and metavariscite (the monoclinic polymorph) are uncommon secondary minerals that are relevant in environmental applications and particularly in technological applications when synthesized in a dehydrated form. Although two orthorhombic modifications are known (so-called "Lucin-type" and "Messbach-type"), the fine-grained nature of the "Messbach-type" variscite has hampered determination of its crystal structure.In this contribution, the crystal structure of the latter (a natural specimen from Tooele County, Utah) has been solved and refined using X-ray powder diffraction data via ab initio charge-flipping methods and the Rietveld method. Our results, structural interpretations, and topological analysis demonstrate that the two orthorhombic structural modifications are polytypes, and we refer to them as variscite1O ("Lucin-type") and as variscite2O ("Messbach-type"), to be consistent with modern polytype terminology. The structure of variscite2O is similar to that of the 1O polymorph, with a doubling of the b unit-cell parameter. The variscite2O crystal structure contains two crystallographically independent Al3+ cations coordinated by two H2O molecules and four oxygen atoms of the PO4 groups. Two crystallographically independent PO4 tetrahedra share their corners with four adjacent AlO4(OH2)2 octahedra. Both orthorhombic polymorphs belong to the family of framework 3D MT structures in which octahedra (M) and tetrahedra (T) are linked by bridging O atoms, and topological analysis suggests that these two structures may be considered polytypes. Similarities between these polytypes, along with observed broadening of diffraction peaks of the Tooele material, suggest that interstratifications of the two forms may exist in nature. Besides the long-range characterization of the crystal structure by X-ray diffraction, information on the short-range structural properties of this mineral have been gained through 31P and 27Al MAS/NMR measurements. Results from NMR corroborate the crystal structure determination and they show distinct signals for each of the two independent P and Al positions in variscite2O. In addition, high-temperature XRD, thermal analyses, and NMR measurements clarified the nature of the transformation of variscite2O to the derivative AlPO4 structure. The crystal structure of this new anhydrous AlPO4 phase (AlPO4-variscite2O in analogy to its parent structure) can be described as a 3D framework of alternating AlO4 and PO4 tetrahedra linked by bridging O atoms. Thermogravimetric analyses revealed almost complete dehydration above ~450K, and NMR results were consistent with Al and P atoms located at tetrahedral sites

Estimating the thermal photon production rate using lattice QCD

We present results for the photon emission rate determined from the transverse channel vector correlator at fixed spatial momentum using two flavors of dynamical Wilson fermions at $T \sim$ 250 MeV. We estimate the transverse channel spectral function using the continuum extrapolated correlator by applying various fit ansätze with a smooth matching to the NLO perturbative result. We confront our estimate based on this channel with the latest results of our collaboration based on the difference of the transverse and longitudinal channels.We present results for the photon emission rate determined from the transverse channel vector correlator at fixed spatial momentum using two flavors of dynamical Wilson fermions at $T\sim$250 MeV. We estimate the transverse channel spectral function using the continuum extrapolated correlator by applying various fit ansätze with a smooth matching to the NLO perturbative result. We confront our estimate based on this channel with the latest results of our collaboration based on the difference of the transverse and longitudinal channels