Real-space effects of a quench in the Su-Schrieffer-Heeger model and elusive dynamical appearance of the topological edge states

The topological phase of the Su-Schrieffer-Heeger (SSH) model is known to exhibit two edge states that are topologically protected by the chiral symmetry. We demonstrate that, for any parameter quench performed on the half-filled SSH chain, the occupancy of each lattice site remains locked to 1/2 at any time, due to the additional time-reversal and charge conjugation symmetries. In particular, for a quench from the trivial to the topological phase, no signature of the topological edge states appears in real-space occupancies, independently of the quench protocol, the temperature of the pre-quench thermal state or the presence of chiral disorder. However, a suitably designed local quench from/to a SSH ring threaded by a magnetic flux can break these additional symmetries while preserving the chiral one. Then, real-space effects of the quench do appear and exhibit different dynamical features in the topological and in the trivial phases. Moreover, when the particle filling is different from a half and the pre-quench state is not insulating, the dynamical appearance of the topological edge states is visible already in a chain, it survives time averaging and can be observed also in the presence of chiral-breaking disorder and for instantaneous quenches.

Measuring and Leveraging Electrostatic Effects in a Charged Phosphine

<div>Local electric fields have recently been investigated for optimizing reactivity in synthetic systems. However, disentangling the relative contributions of inductive (through-bond) and electrostatic (through-space) effects in molecular systems has been a long-standing challenge. To understand the interplay of these effects and leverage electrostatic influences for enhanced reactivity, we have synthesized a distally charged phosphine, Ph₂PCH₂BF₃⁻, and studied the effect of the charged trifluoroborate group on its donor properties and reactivity. This charged phosphine displays solvent-dependent changes in donor strength as measured by the <i>J</i>_P-Se of the corresponding phosphine selenide. The variation with solvent dielectric illustrates a significant electrostatic component to the donor strength. Computations further support the importance of electrostatic contributions and highlight the effect of charge position and orientation. Finally, this charged group also greatly accelerates C–F oxidative addition reactivity in Ni complexes, experimentally</div><div>verifying recent theoretical predictions. These results show that covalently bound charged functionalities can exert a significant electrostatic influence even under common solution phase reaction conditions.</div>

Measuring and Leveraging Electrostatic Effects in a Charged Phosphine

<div>Local electric fields have recently been investigated for optimizing reactivity in synthetic systems. However, disentangling the relative contributions of inductive (through-bond) and electrostatic (through-space) effects in molecular systems has been a long-standing challenge. To understand the interplay of these effects and leverage electrostatic influences for enhanced reactivity, we have synthesized a distally charged phosphine, Ph₂PCH₂BF₃⁻, and studied the effect of the charged trifluoroborate group on its donor properties and reactivity. This charged phosphine displays solvent-dependent changes in donor strength as measured by the <i>J</i>_P-Se of the corresponding phosphine selenide. The variation with solvent dielectric illustrates a significant electrostatic component to the donor strength. Computations further support the importance of electrostatic contributions and highlight the effect of charge position and orientation. Finally, this charged group also greatly accelerates C–F oxidative addition reactivity in Ni complexes, experimentally</div><div>verifying recent theoretical predictions. These results show that covalently bound charged functionalities can exert a significant electrostatic influence even under common solution phase reaction conditions.</div>

Redshift-space effects in voids and their impact on cosmological tests. Part I: the void size function

ABSTRACT Voids are promising cosmological probes. Nevertheless, every cosmological test based on voids must necessarily employ methods to identify them in redshift space. Therefore, redshift-space distortions (RSD) and the Alcock–Paczyński effect (AP) have an impact on the void identification process itself generating distortion patterns in observations. Using a spherical void finder, we developed a statistical and theoretical framework to describe physically the connection between the identification in real and redshift space. We found that redshift-space voids above the shot noise level have a unique real-space counterpart spanning the same region of space, they are systematically bigger and their centres are preferentially shifted along the line of sight. The expansion effect is a by-product of RSD induced by tracer dynamics at scales around the void radius, whereas the off-centring effect constitutes a different class of RSD induced at larger scales by the global dynamics of the whole region containing the void. The volume of voids is also altered by the fiducial cosmology assumed to measure distances, this is the AP change of volume. These three systematics have an impact on cosmological statistics. In this work, we focus on the void size function. We developed a theoretical framework to model these effects and tested it with a numerical simulation, recovering the statistical properties of the abundance of voids in real space. This description depends strongly on cosmology. Hence, we lay the foundations for improvements in current models of the abundance of voids in order to obtain unbiased cosmological constraints from redshift surveys.

Effects of Smoking, Drinking, and Urban Environment on Obesity in Seoul, Korea

Background: The level of obesity is related to spatial characteristics around the individual. The objective of this study was to empirically analyze the effect of smoking, drinking, and urban environment on obesity in community residents. Methods: This study was conducted for empirical analysis using Ordinary Least Squares (OLS) model not considering time or space-effects, Temporal Autoregressive (TAR) model considering time-effect only, Spatial Autoregressive (SAR) model considering space-model only, and STAR model considering both time and space effects. This study covered 25 autonomous districts in Seoul City, South Korea in terms of space and from 2009 to 2014 in terms of time. Results: The STAR model yielded an adjusted R square higher than that from OLS, TAR, or SAR model. Empirical results from the STAR model showed significantly positive (+) effects of the ratio of dependent elders, ratio of smokers, ratio of drinkers, and areas of retail floor space on obesity. In contrast, effects of length of bicycle road and the amount of collected local tax on obesity were negative (-) with statistical significance. Conclusion: Smoking and drinking rate and the length of bicycle road can contribute to personal obesity.