The Relationship Between Vegetation Characteristics and Altitudes in Transitional Permafrost Zone in Xidatan, Qinghai-Tibetan Plateau

Many studies showed that permafrost has profound influence on alpine ecosystem. However, former researches were mainly focused on typical points by temporal scales. There were few studies about the correlation between vegetation characteristics and different altitudes covering a large region in spatial pattern, especially in transitional permafrost(TP). There were continuous permafrost(CP) discontinuous permafrost(DCP) and seasonal frozen ground(SFG) in this study region. The types of permafrost changed from SFG to DCP, and finally become CP as the altitudes of Xidatan increase. In this paper, 112 845 points interpreted by HJ1-B(environment and disaster monitoring and prediction small satellite constellation), vegetation investigation points, thawing layer thickness research sites, ground temperature and water content observation plots were used to examine the spatial pattern of vegetation which were located in different altitudes in Xidatan, a typical TP region, in Qinghai-Tibetan Plateau. Vegetation characteristics, soil moisture content(SMC) and thaw depths were collected in 15 August to 25 August2012. Characteristics of vegetation were mainly represented by fractional vegetation cover(FVC) derived from the normalized difference vegetation index(NDVI), as well as above ground biomass(AGB). In this paper, we analyzed that the distinction of vegetation characteristics in each range through statistics data. These ranges were divided by varied altitudes. For examples, the ranges were divided into 50 m or 100 m. In this study we use a large area plots method to further discuss the relationship between the features of vegetation and the different regions of permafrost based on altitudes shifts in Xidatan. A diagram described the vegetation characteristics variability with rising altitudes in transitional permafrost region was drawn in this paper. Our results illustrated the FVCs first increased in SFG region and then decreased in DCP zone slowly, and in CP region FVCs soared then dropped dramatically. With the altitudes increased, the curve of FVCs indicated a parabolic distribution except a little difference in the first 200 m range.

Geometrical characterization of reduced density matrices reveals quantum phase transitions in many-body systems

Quantum phase transitions (QPTs) play a central role for understanding many-body physics [1]. Different from classical phase transitions which are driven by thermal fluctuations, QPTs are driven by quantum fluctuations at zero temperature and can be accessed by varying some physical parameters of the many-body system. Characterizing QPTs, which normally needs complicated theoretical calculations, becomes a fundamental problem to further study quantum matters. Here a group of physicists proposed to connect the geometrical properties of reduced density matrices (RDMs) of the physical system with its quantum phase transitions [2,3]

Thermodynamics under the impact of thermal fluctuations and quasi-normal modes of Euler-Heisenberg AdS BH in the framework of NLED

We study the impact of thermal fluctuations on the thermodynamics,quasi-normal modes,and phase transitions of an anti-de Sitter Euler-Heisenberg black hole(BH)with a nonlinear electrodynamic field.An anti-de Sitter Euler-Heisenberg BH with a nonlinear electrodynamic field is composed of four parameters:the mass,electric charge,cosmological constant,and Euler-Heisenberg parameter.We calculate thermodynamic variables such as Hawking temperature,entropy,volume,and specific heat,which comply with the first law of thermodynamics.First,we use this BH to determine the thermodynamics and thermal fluctuations with the Euler-Heisenberg parameter to distinguish their effect on uncorrected and corrected thermodynamical quantities.We derive the expression for corrected entropy to study the impact of thermal fluctuation with simple logarithmic corrections on unmodified thermodynamical potentials,including Helmholtz energy,pressure,Gibbs free energy,and enthalpy.The Euler-Heisenberg parameter improves BH stability at large radii.Second,we analyze the local stability of the proposed BH,and the phase shifts of the BH are also investigated using temperature and specific heat.When there is a decrease in charge and an increase in r_(+)andα,the temperature shifts from an unstable region to a stable one.Similarly,increases in local stability are observed with each of these parameters.Third,we use null geodesics to deal with the effects of nonlinear electrodynamics on the quasi-normal modes of the Euler-Heisenberg anti-de Sitter BH.The null geodesics provide the angular velocity and Lyapunov exponent of the photon sphere,which are the same as the real and imaginary parts of the quasi-normal modes in the eikonal limit.