Genus stabilization for the components of moduli spaces of curves with symmetries

In a previous paper, arXiv:1206.5498, we introduced a new homological invariant \e for the faithful action of a finite group G on an algebraic curve. We show here that the moduli space of curves admitting a faithful action of a finite group G with a fixed homological invariant \e, if the genus g' of the quotient curve is sufficiently large, is irreducible (and non empty iff the class satisfies the condition which we define as 'admissibility'). In the unramified case, a similar result had been proven by Dunfield and Thurston using the classical invariant in the second homology group of G, H_2(G, \ZZ). We achieve our result showing that the stable classes are in bijection with the set of admissible classes \e

RSA, CMJ, Leger, 10m sprint responses to Pre-season training in semi-Professional Soccer Players

Aim: The aim of this study was to analyze RSA, CMJ, Leger, 10m sprint responses to Pre-season Training in Semi-Professional Soccer Players (SPSP). Considering that numerous studies1,2 highlighted the combination of high levels of physical, technical and tactical skills during a soccer match, the cure of physical training pose a particular attention on training load that generally increases up to 2.4 times during the pre-season period compared with the in-season3. Methods: Six SPSP (age: 23±7yr; BMI: 23.3±1.8) were requested to perform aerobic training over an 8-week period on alternate days with the functional strength training sessions and sprint training drills as prescribed by the coaches and strength and conditioning staff. Repeated Sprint Ability (RSA, Total Time –TT- and percentage of fatigue index -%FI), Leger, 10m sprint and Counter Mouvement Jump (CMJ) tests, were performed before and after pre-season soccer training. ANOVA for repeated measures was conducted to assess differences (p<0.05) with respect to pre seasonal training. Correlation was calculated between the percentage of variation (Δ) of each test. Results: Compared to the values recorded before the pre-season, improvement of Leger (3%) and %FI (17.6%) and a deterioration of TT (10%), 10m sprint (0.2%) and CMJ (2.4%) were found. In addition, we have found a main effect between before and after pre-seasonal training in TT (F(1,4)=60.2; p=0.001) and Leger (F(1,5)=25; p<0.005). ΔCMJ showed very large correlation with ΔLeger (r=-0.88) and nearly perfect with Δ%FI (r=0.93); while ΔLeger was largely correlated with Δ%FI (r=-0.69). Conclusions: Given that the cure of the physical preparation is considered as an important element in order to influence the final soccer game result, this study want to be useful information for the coach in order to maximize the best physical condition of the whole team relative to the beginning of the regular season

Infrared conductivity of a one-dimensional charge-ordered state: quantum lattice effects

The optical properties of the charge-ordering ($CO$) phase of the one-dimensional (1D) half-filled spinless Holstein model are derived at zero temperature within a well-known variational approach improved including second-order lattice fluctuations. Within the $CO$ phase, the static lattice distortions give rise to the optical interband gap, that broadens as the strength of the electron-phonon ($el-ph$) interaction increases. The lattice fluctuation effects induce a long subgap tail in the infrared conductivity and a wide band above the gap energy. The first term is due to the multi-phonon emission by the charge carriers, the second to the interband transitions accompanied by the multi-phonon scattering. The results show a good agreement with experimental spectra.Comment: 5 figure

Effects of competition level on the centre forward role of men&#8217;s water polo.

This study aimed to compare specific technical and tactical indicators of the team and centre forward role of Euro League, and Italian Serie A1, Serie A2, and Serie B men's water polo club competitions. A notational analysis was performed on 21 water polo matches to evaluate the occurrence of technical and tactical team and centre forward indicators, highlighting differences among championships according to chi-square analyses. Differences emerged for Counterattack (P < 0.001) and Power-Play (P < 0.001) possessions, Even (P < 0.001; Euro League: 3 ± 1, Serie A1: 3 ± 2, Serie A2: 3 ± 2, Serie B: 6 ± 4) and Power-Play (P = 0.001) goals, and exclusions and penalties (P = 0.008) of the team during Even possessions. Relatively to the role analyses, effects emerged for perimeter players playing events (P = 0.049), as well as for centre forwards' goals (P = 0.007) and exclusions and penalties (P < 0.001; Euro League: 8 ± 1, Serie A1: 6 ± 2, Serie A2: 6 ± 2, Serie B: 3 ± 2) occurring at the end of Even possessions. Therefore, in Euro League, and Italian Serie A1 and Serie A2, teams perform a high occurrence of Power-Play possessions following up an exclusion, especially achieved by the centre forward during Even possessions, while, in Italian Serie B, goals were mostly scored during Even possessions, with a relevant contribution from the centre forward rol

Heart rate responses and technical-tactical aspects of official 5-a-side youth soccer matches played on soil and artificial turf.

Using a randomized crossover design, this study aimed to compare the heart rate (HR) responses and match analysis parameters (i.e., type of action; the number of players involved in an action; the number of passes performed in a collective action; precision of the shots; lost balls; ball interceptions; dribblings; and tackles) of official 5-a-side youth male soccer matches played over 2 pitch surface (i.e., clay vs. artificial turf) conditions. Twenty-two young male soccer players (age 8.3 6 0.4 years) engaged in 2 consecutive 15-minute periods in each experimental condition. During the match, 53% of HR responses exceeded 85% of the individual HRpeak. No difference emerged between both pitch surfaces and match periods for HR and match analysis indicators. The two 15-minute periods resulted in being appropriate for 8-year-old players, in resembling the intensity of play and the intermittent nature of adult soccer. The similar HR responses and technical-tactical patterns observed on the 2 surfaces indicate that youth match play is not affected by differences in pitch surface. To support the development of individual and team skills of young soccer players, coaches are advised to prioritize game knowledge based on divergent thinking and experience, rather than traditional teaching based on instructions

Physical activity, sedentary behaviour and screen time among youths with Down syndrome during the COVID-19 pandemic

Background: The COVID-19-related restrictions hampered habitual physical activity (PA), particularly affecting the more vulnerable, such as people with Down syndrome (DS). The study aimed to investigate changes in PA, sedentary behaviour (SB) and screen time (ST) of youths with DS, before, during and after the restrictions, also in relation to parental PA levels. Methods: A cross-sectional design with a retrospective assessment of variables for the before and during restrictions periods was adopted. Parents of youths with DS completed an online questionnaire. Sociodemographic aspects, weekly PA levels and youths' daily SB and ST were investigated, referring to three time-points: before the pandemic, during the restrictions and the restrictions-easing phase. Results: A total of 57 parents voluntarily participated in the study, proxy-reporting on their child (male = 41, female = 16, age = 21.4 ± 7.7 years). A repeated measures multivariate analysis of variance showed negative effects of restrictions (P < 0.05) on PA levels, SB and ST, independently from sociodemographic characteristics. In the restrictions-easing phase, PA levels did not return to before the pandemic values (P < 0.05). A positive correlation between parents and their child's PA was detected before the pandemic (r = 0.38; P < 0.01), no longer reported in the restrictions-easing phase. Conclusions: The findings showed the negative impact of restrictions on youths with DS lifestyle. Moreover, the importance of addressing the needs of the disabled community including the whole family is highlighted

Multiple double-exchange mechanism by Mn2+^{2+}-doping in manganite compounds

Double-exchange mechanisms in RE$_{1-x}$AE$_{x}$MnO$_{3}$ manganites (where RE is a trivalent rare-earth ion and AE is a divalent alkali-earth ion) relies on the strong exchange interaction between two Mn$^{3+}$ and Mn$^{4+}$ ions through interfiling oxygen 2p states. Nevertheless, the role of RE and AE ions has ever been considered "silent" with respect to the DE conducting mechanisms. Here we show that a new path for DE-mechanism is indeed possible by partially replacing the RE-AE elements by Mn$^{2+}$-ions, in La-deficient La$_{x}$MnO$_{3-\delta}$ thin films. X-ray absorption spectroscopy demonstrated the relevant presence of Mn$^{2+}$ ions, which is unambiguously proved to be substituted at La-site by Resonant Inelastic X-ray Scattering. Mn$^{2+}$ is proved to be directly correlated to the enhanced magneto-transport properties because of an additional hopping mechanism trough interfiling Mn$^{2+}$-ions, theoretically confirmed by calculations within the effective single band model. The very idea to use Mn$^{2+}$ both as a doping element and an ions electronically involved in the conduction mechanism, has never been foreseen, revealing a new phenomena in transport properties of manganites. More important, such a strategy might be also pursed in other strongly correlated materials.Comment: 6 pages, 5 figure

Modelling of strain effects in manganite films

Thickness dependence and strain effects in films of $La_{1-x}A_xMnO_3$ perovskites are analyzed in the colossal magnetoresistance regime. The calculations are based on a generalization of a variational approach previously proposed for the study of manganite bulk. It is found that a reduction in the thickness of the film causes a decrease of critical temperature and magnetization, and an increase of resistivity at low temperatures. The strain is introduced through the modifications of in-plane and out-of-plane electron hopping amplitudes due to substrate-induced distortions of the film unit cell. The strain effects on the transition temperature and transport properties are in good agreement with experimental data only if the dependence of the hopping matrix elements on the $Mn-O-Mn$ bond angle is properly taken into account. Finally variations of the electron-phonon coupling linked to the presence of strain turn out important in influencing the balance of coexisting phases in the filmComment: 7 figures. To be published on Physical Review