Emergent self-duality in long range critical spin chain: from deconfined criticality to first order transition

Over the past few decades, tremendous efforts have been devoted to understanding self-duality at the quantum critical point, which enlarges the global symmetry and constrains the dynamics. In this letter, we employ large-scale density matrix renormalization group simulations to investigate the critical spin chain with long-range interaction $V(r) \sim 1/r^{\alpha}$. Remarkably, we reveal that the long-range interaction drives the deconfined criticality towards a first-order phase transition as $\alpha$ decreases. More strikingly, the emergent self-duality leads to an emergent symmetry and manifests at these first-order critical points. This discovery is reminiscent of self-duality protected multicritical points and provides the example of the critical line with generalized symmetry. Our work has far-reaching implications for ongoing experimental efforts in Rydberg atom quantum simulators.Comment: 5 + 10 pages, 9 figures. Any comments or suggestions are welcome

Inhibition of stimulated Raman scattering due to the excitation of stimulated Brillouin scattering

The nonlinear coupling between stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) of intense laser in underdense plasma is studied theoretically and numerically. Based upon the fluid model, their coupling equations are derived, and a threshold condition of plasma density perturbations due to SBS for the inhibition of SRS is given. Particle-in-cell simulations show that this condition can be achieved easily by SBS in the so-called fluid regime with kLλD<0.15, where kL is the Langmuir wave number and λD is the Debye length [Kline et al., Phys. Plasmas 13, 055906 (2006)]. SBS can reduce the saturation level of SRS and the temperature of electrons in both homogeneous and inhomogeneous plasma. Numerical simulations also show that this reduced SRS saturation is retained even if the fluid regime condition mentioned above is violated at a later time due to plasma heating

Poly[[[diaqua­cobalt(II)]-bis­[μ2-1,1′-(butane-1,4-di­yl)diimidazole-κ2 N 3:N 3′]] dinitrate]

In the title compound, {[Co(C10H14N4)2(H2O)2](NO3)2}n, the CoII ion lies on an inversion center and is six-coordinated in an octa­hedral environment by four N atoms from four different 1,1′-butane-1,4-diyldiimidazole ligands and two O atoms from the two water mol­ecules. The CoII atoms are bridged by ligands, generating a two-dimensional (4,4)-network. Adjacent fishnet planes are linked to the nitrate anions via O—H⋯O hydrogen bonds, forming a three-dimensional supra­molecular structure

On the Effect of Lubricant on Pool Boiling Heat Transfer Performance

   For typical vapor compression processes, lubricant oil is very essential for lubricating and sealing the sliding parts and the lubricant also takes part in cushioning cylinder valves. However lubricants may migrate to the evaporator to alter the heat transfer characteristics. This is can be made clear from the viscosity and surface tension of lubricant since the viscosity of lubricant oil is about two to three orders higher than that of refrigerant whereas the corresponding surface tension of lubricant is approximately one order higher. Typically, the presence of lubricant may deteriorate heat transfer performance, yet this phenomenon becomes more severe when the lubricant mass fraction is higher. However, some previous literatures had clearly showed that the presence of lubricant oil may favor the heat transfer performance at a low lubricant fraction and the heat transfer performance may peak at a specific oil concentration. In this study, the authors aim at clarifying this phenomenon subject to pool boiling condition. Various parameters affecting the heat transfer coefficient, such as viscosity, surface tension, critical solution temperature and other thermodynamic and transport properties will be examined.    During pool boiling process, the lubricant accumulates on the surface since the refrigerant is preferential to evaporate. Hence, excess lubricant enrichment on the surface results in a thin lubricant excess layer and a thermal boundary layer, which influence the heat transfer performance, either enhancement or degradation. The excess layer may bring about a liquid-solid surface energy reduction which increases site density and reduces the bubble departure diameter, causing enhancement and degradation in heat transfer performance, respectively. However, the effect of the bubble departure diameter normally surpasses the influence of site density. This may be the crucial reason that gives rise to an occurrence of the plateau of heat transfer coefficient and followed by an apparent decline of heat transfer coefficient with a further increase of lubricant concentration.    Moreover, with the preferential evaporation of the refrigerant, a surface tension gradient is formed, which induces the Marangoni effect through which refrigerant/lubricant mixtures is supplied toward the contact line. From the phase equilibrium diagram, the maximum of the Marangoni number may occur at the low lubricant concentration with a maximum temperature difference. Hence, the presence of Marangoni effect may also be the favor the heat transfer accordingly. Also, a small fraction of lubricant will increase a larger viscosity that provide a thicker thermal boundary layer which may activate more site density, and enhances the heat transfer performance. Furthermore, miscibility may also play a crucial factor that affects the pool boiling heat transfer performance. The fluid with a smaller difference between the bulk fluid temperature and critical solution temperature may yield a better heat transfer performance by drawing superheated liquid onto the bubble sides.

The Effect of Refrigeration Lubricant Properties on Nucleate Pool Boiling Heat Transfer Performance

Refrigeration lubricant plays a key role in lubricating and sealing during vapor compression processes. However, it may migrate to the evaporator to influence the heat transfer characteristics, either enhancement or degradation. The aim of this study is to fundamentally understand the effect of lubricant properties and bubble parameters on heat transfer performance. To clarify parameters affecting the heat transfer coefficient, several experiments were conducted on a horizontal flat surface, and pool-boiling phenomenon was recording by high-speed camera. Comparisons of heat transfer measurements for different refrigerant/lubricant mixtures were made, including two different refrigerants (R-134a & R-1234ze) and eight POE lubricants with different miscibility, ISO68 to ISO170 viscosity range. This study shows that improvements over pure refrigerant heat transfer can be obtained for refrigerant /lubricant mixtures with small lubricant mass fraction, high lubricant viscosity, and a low critical solution temperature (CST). The presence of lubricant will decrease the departure bubble diameter and may deteriorate heat transfer performance when the lubricant mass fraction is higher than 3%. A mechanistic explanation was provided for the observed refrigerant/lubricant boiling phenomenon, and we were successfully in creating a new model to quantify the effect of lubricant properties on the heat transfer performance. This model was developed based on cavity boiling theory, interfacial energy calculation between metal-liquid surface, and liquid-bubble interface. According to the model, the presence of lubricant layer on metal surface and surrounding the bubble will significantly alter waiting time of boiling, bubble departure time, activity site density of boiling incipience and superheat on heating surface