Bubble nucleation in the two-flavor quark-meson model

We investigate the dynamics of a first-order quark-hadron transition via homogeneous thermal nucleation in the two-flavor quark-meson model.The contribution of the fermionic vacuum loop in the effective thermodynamics potential and phase diagram,together with the location of the critical endpoint(CEP),is obtained in the temperature and chemical potential plane.For weak and strong first-order phase transitions,by taking the temperature as a variable,the critical bubble profiles,evolutions of the surface tension,and saddle-point action in the presence of a nucleation bubble are numerically calculated in detail when fixing the chemical potentials atμ=306 MeV andμ=309 MeV.Our results show that the system could be trapped in the metastable state for a long time as long as the temperature is between the metastable region characterized by the up and low spinodal lines.Moreover,the surface tension at criticality will rise to approximately 4 MeV/fm2 when the chemical potential is very high.Such a small surface tension value would favor a mixed phase in the cores of compact stars and may have an important implication in astrophysics.

A comparison research on replacements of Ba^(2+)by Lu^(3+)and Ba^(2+)-Si^(4+)by Lu^(3+)-Al^(3+)in BaSi_(2)O_(2)N_(2):Eu phosphors

As a cyan-emitting oxonitridosilicate phosphor,BaSi_(2)O_(2)N_(2):Eu^(2+)can be used as a competent cyan compensator to improve the color rendering index of white light-emitting diodes(WLEDs).However,low luminescence efficiency and poor thermal stability of this type of phosphor seriously suppress its actual application in full-spectrum lighting.The replacements of Ba^(2+)by Lu^(3+)and Ba^(2+)-Si^(4+)by Lu^(3+)-Al^(3+)can greatly increase the luminescence intensity and improve the thermal stability at the same time.With Lu^(3+)doping,the internal quantum efficiencyηIQE Ba_(0.925)Si_(2)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+)is 24.08%higher than that of Ba_(0.97)Si_(2)O_(2)N_(2):0.03 Eu^(2+).After Al^(3+)co-doping,theηIQE is further increased by 10.31%compared to Ba_(0.925)Si_(2)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+).When the temperature rises to 473 K,the luminescence intensity of Ba_(0.925)Si_(2)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+)maintains 62.32%of that at room temperature,which increases by 17.35%in relative to the Ba_(0.97)Si_(2)O_(2)N_(2):0.03 Eu^(2+),while the luminescence intensity of Ba_(0.925)Si_(1.97)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+),0.03 Al^(3+)keeps 73.87%of the initial value,which increases by18.52%compared to Ba_(0.925)Si_(2)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+).The mechanisms for luminescence and thermal stability improvement are proposed.The Ba_(0.925)Si_(1.97)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+),0.03 Al^(3+)cyan phosphor,Y3 Al5 O12:Ce3+yellow phosphor and CaAlSiN3:Eu^(2+)red phosphor are mixed thoroughly and coated on a blue LED(450 nm)to assemble a WLED.The WLED demonstrates a color rendering index(Ra)of 97.1 at150 mA,and the R1-R15 values are all above 90.The results indicate that as an effective cyan compensator in WLED,the BaSi_(2)O_(2)N_(2):Eu^(2+),Lu^(3+),Al^(3+)phosphor has great application prospect in the field of full-spectrum lighting.