87,820 research outputs found
Critical behaviours of contact near phase transitions
A central quantity of importance for ultracold atoms is contact, which
measures two-body correlations at short distances in dilute systems. It appears
in universal relations among thermodynamic quantities, such as large momentum
tails, energy, and dynamic structure factors, through the renowned Tan
relations. However, a conceptual question remains open as to whether or not
contact can signify phase transitions that are insensitive to short-range
physics. Here we show that, near a continuous classical or quantum phase
transition, contact exhibits a variety of critical behaviors, including scaling
laws and critical exponents that are uniquely determined by the universality
class of the phase transition and a constant contact per particle. We also use
a prototypical exactly solvable model to demonstrate these critical behaviors
in one-dimensional strongly interacting fermions. Our work establishes an
intrinsic connection between the universality of dilute many-body systems and
universal critical phenomena near a phase transition.Comment: Final version published in Nat. Commun. 5:5140 doi:
10.1038/ncomms6140 (2014
Comparative study of commercial building energy-efficiency retrofit policies in four pilot cities in China
The energy efficiency of existing commercial buildings is more challenging to regulate and improve than the energy efficiency of new constructions. In 2011 and 2012, the Chinese Government selected four cities- Shanghai, Tianjin, Shenzhen, and Chongqing- to implement pilot commercial building energy efficiency retrofit program. Based on site surveys and expert interviews in these pilot cities, this research conducted a comparative analysis on incentive policies of local city level. The analysis results show that policy designs of existing commercial buildings should be further improved. The aspects that influence the implementation effect in the future, such as subsidy level, installments, and business model promotion, should be specified in the policy clauses. Referring to the technical solution and cost-benefit in Chongqing, we found that lighting system is the most common retrofit objects while envelope system is the least common one. And the subsidy incentive is greatest for educational buildings, followed by office buildings. In the end, we further discussed the problems and obstacles in commercial building retrofit market, and provided a series of recommendations
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