Relaxing the cosmological constant: a proof of concept

We propose a technically natural scenario whereby an initially large cosmological constant (c.c.) is relaxed down to the observed value due to the dynamics of a scalar evolving on a very shallow potential. The model crucially relies on a sector that violates the null energy condition (NEC) and gets activated only when the Hubble rate becomes sufficiently small — of the order of the present one. As a result of NEC violation, this low-energy universe evolves into inflation, followed by reheating and the standard Big Bang cosmology. The symmetries of the theory force the c.c. to be the same before and after the NEC-violating phase, so that a late-time observer sees an effective c.c. of the correct magnitude. Importantly, our model allows neither for eternal inflation nor for a set of possible values of dark energy, the latter fixed by the parameters of the theory

An E7 Surprise

We explore some curious implications of Seiberg duality for an SU(2) four-dimensional gauge theory with eight chiral doublets. We argue that two copies of the theory can be deformed by an exactly marginal quartic superpotential so that they acquire an enhanced E7 flavor symmetry. We argue that a single copy of the theory can be used to define an E7-invariant superconformal boundary condition for a theory of 28 five-dimensional free hypermultiplets. Finally, we derive similar statements for three-dimensional gauge theories such as an SU(2) gauge theory with six chiral doublets or Nf=4 SQED.Comment: 27 page

Tribological behavior of 316L stainless steel reinforced with CuCoBe + diamond composites by laser sintering and hot pressing: a comparative statistical study

The aim of this work was to perform a statistical analysis in order to assess how the tribological properties of a laser textured 316L stainless steel reinforced with CuCoBe - diamond composites are affected by diamond particles size, type of technology (laser sintering and hot pressing) and time of tribological test. The analysis started with the description of all response variables. Then, by using IBM® SPSS software, the Friedman’s test was used to compare how the coefficient of friction varied among samples in five-time points. From this test, results showed that there was no statistically significant difference in the coefficient of friction mean values over the selected time points. Then, the two-samples Kolmogorov-Smirnov (K-S) test was used to test the effect of the diamond particles size and the type of technology on the mean of the coefficient of friction over time. The results showed that, for both sintering techniques, the size of the diamond particles significantly affected the values of the coefficient of friction, whereas no statistical differences were found between the tested sintering techniques. Also, the two-way ANOVA test was used to evaluate how these factors influence the specific wear rate, which conducted to the same conclusions drawn for the previous test. The main conclusion was that the coefficient of friction and the specific wear rate were statistically affected by the diamond particles size, but not by the sintering techniques used in this work.This work was supported by FCT national funds, under the national support to R&D units grant, through the reference projects UIDB/04436/2020 and UIDP/04436/2020. Additionally, this work was supported by FCT with the reference projects UIDB/00319/2020 and PTDC/CTM-COM/30416/2017

Изучение электрокинетических возможностей сепарации и концентрирования бактерий (S.aureus) в цельной крови четырехэлектродным биосенсорным чип-форматом с прозрачными микроэлектродами

The electrokinetic possibilities of separation and concentration of S.aureus bacteria in human whole blood (test mixture) were studied using a new design of a four-electrode biosensor chip format with transparent microelectrodes. In the measurements, a closed cell was used, into which the test mixture was poured. The electrokinetic movement of bacteria during concentration was observed when AC voltage was applied to the first and second annular external electrodes, and DC voltage was applied to the third and fourth semicircular central electrodes. The process of separation of erythrocytes and concentration of bacteria was recorded by an optical method. It is shown that the concentration of bacteria appears after 8 minutes and increases by 30 minutes in the region of the central electrodes under model conditions. The measurements were carried out on two biosensor chip formats having almost identical electrophysical parameters of capacitance and conductivity at frequencies from 100 Hz to 1 MHz. It is determined that the amplitude-frequency mode and biosensor chip format can be used to develop methodological support for the identification of bacterial species, but only by optical methods. It is shown that in order to increase the number of bacteria on both of the central electrode in the concentration mode, it is necessary to increase the speed of the electroosmotic flow at alternating current, by optimizing the composition of the medium and the parameters of the electrical regime in order to equalize the rates of separation and concentration processes.Изучены электрокинетические возможности сепарации и концентрирования бактерий S.aureus в цельной крови человека (исследуемая смесь) с помощью новой конструкции четырехэлектродного биосенсорного чип-формата с прозрачными микроэлектродами. В исследованиях использована закрытая ячейка, в которую заливали исследуемую смесь. Электрокинетическое перемещение бактерий при концентрировании наблюдалось при подаче на первый и второй кольцевые внешние электроды переменного напряжения, а на третий и четвертый полукруглые центральные электроды – постоянного напряжения. Процесс сепарации эритроцитов и концентрирования бактерий фиксировался оптическим методом для модельных условий и в цельной крови. Показано, что концентрирование бактерий проявляется через 8 минут и увеличивается к 30 минуте в области центральных электродов в модельных условиях. Измерения были проведены на биосенсорных чип-форматах, имеющих практически одинаковые электрофизические параметры емкости и проводимости на частотах от 100 Гц до 1 МГц. Установлено, что амплитудно-частотный режим и биосенсорный чип-формат могут быть использованы для разработки методического обеспечения идентификации вида бактерий, но только оптическими методами. Показано, что для увеличения количества бактерий на центральных электродах в режиме концентрирования необходимо повысить скорость электроосмотического потока на переменном токе путем оптимизации состава среды и параметров электрического режима, чтобы уравнять скорости процессов сепарации и концентрирования

Elliptic hypergeometry of supersymmetric dualities II. Orthogonal groups, knots, and vortices

We consider Seiberg electric-magnetic dualities for 4d $\mathcal{N}=1$ SYM theories with SO(N) gauge group. For all such known theories we construct superconformal indices (SCIs) in terms of elliptic hypergeometric integrals. Equalities of these indices for dual theories lead both to proven earlier special function identities and new conjectural relations for integrals. In particular, we describe a number of new elliptic beta integrals associated with the s-confining theories with the spinor matter fields. Reductions of some dualities from SP(2N) to SO(2N) or SO(2N+1) gauge groups are described. Interrelation of SCIs and the Witten anomaly is briefly discussed. Possible applications of the elliptic hypergeometric integrals to a two-parameter deformation of 2d conformal field theory and related matrix models are indicated. Connections of the reduced SCIs with the state integrals of the knot theory, generalized AGT duality for (3+3)d theories, and a 2d vortex partition function are described.Comment: Latex, 58 pages; paper shortened, to appear in Commun. Math. Phy