3,346 research outputs found
Diquark mass differences from unquenched lattice QCD
We calculate diquark correlation functions in the Landau gauge on the lattice
using overlap valence quarks and 2+1-flavor domain wall fermion configurations.
Quark masses are extracted from the scalar part of quark propagators in the
Landau gauge. Scalar diquark quark mass difference and axial vector scalar
diquark mass difference are obtained for diquarks composed of two light quarks
and of a strange and a light quark. Light sea quark mass dependence of the
results is examined. Two lattice spacings are used to check the discretization
effects. The coarse and fine lattices are of sizes and
with inverse spacings and , respectively.Comment: 9 figure
The Lifecycle and Cascade of WeChat Social Messaging Groups
Social instant messaging services are emerging as a transformative form with
which people connect, communicate with friends in their daily life - they
catalyze the formation of social groups, and they bring people stronger sense
of community and connection. However, research community still knows little
about the formation and evolution of groups in the context of social messaging
- their lifecycles, the change in their underlying structures over time, and
the diffusion processes by which they develop new members. In this paper, we
analyze the daily usage logs from WeChat group messaging platform - the largest
standalone messaging communication service in China - with the goal of
understanding the processes by which social messaging groups come together,
grow new members, and evolve over time. Specifically, we discover a strong
dichotomy among groups in terms of their lifecycle, and develop a separability
model by taking into account a broad range of group-level features, showing
that long-term and short-term groups are inherently distinct. We also found
that the lifecycle of messaging groups is largely dependent on their social
roles and functions in users' daily social experiences and specific purposes.
Given the strong separability between the long-term and short-term groups, we
further address the problem concerning the early prediction of successful
communities. In addition to modeling the growth and evolution from group-level
perspective, we investigate the individual-level attributes of group members
and study the diffusion process by which groups gain new members. By
considering members' historical engagement behavior as well as the local social
network structure that they embedded in, we develop a membership cascade model
and demonstrate the effectiveness by achieving AUC of 95.31% in predicting
inviter, and an AUC of 98.66% in predicting invitee.Comment: 10 pages, 8 figures, to appear in proceedings of the 25th
International World Wide Web Conference (WWW 2016
RI/MOM and RI/SMOM renormalization of overlap quark bilinears on domain wall fermion configurations
Renormalization constants (RCs) of overlap quark bilinear operators on
2+1-flavor domain wall fermion configurations are calculated by using the
RI/MOM and RI/SMOM schemes. The scale independent RC for the axial vector
current is computed by using a Ward identity. Then the RCs for the quark field
and the vector, tensor, scalar and pseudoscalar operators are calculated in
both the RI/MOM and RI/SMOM schemes. The RCs are converted to the
scheme and we compare the numerical results from using the
two intermediate schemes. The lattice size is and the inverse
spacing .Comment: Minor changes and updates of Figure 10 and 15 to be more clea
Superradiant Transition to a Fermionic Quasicrystal in a Cavity
Recently, the steady state superradiance in degenerate Fermi gases has been
realized in a cavity, following the previous discovery of the Dicke transition
in Bose gases. The most prominent signature of fermionic Dicke transition is
its density dependence, which is manifested as the Fermi surface nesting effect
and the Pauli blocking effect. We study the superradiant transition in
one-dimensional Fermi gases in a cavity with the presence of an incommensurate
dipolar lattice. We find a first-order Dicke transition induced by indirect
resonance effect, which is a resonance between two atomic levels by the level
repulsion from a third level, and causes extra gap opening. By formulating a
phenomenological theory, we find that the critical pumping strength for this
first-order Dicke transition shows a linear V-shape kink near a particular
indirect resonance modified filling . The presence and the
unique density dependence of this transition manifest the fermionic nature and
verify the mechanism of the quasicrystal superradiant transition.Comment: 5+8 pages, 3+6 figure
- …