683 research outputs found
Universal Jump in the Helicity Modulus of the Two-Dimensional Quantum XY Model
The helicity modulus of the S=1/2 XY model is precisely estimated through a
world line quantum Monte Carlo method enhanced by a cluster update algorithm.
The obtained estimates for various system sizes and temperatures are well
fitted by a scaling form with L replaced by \log(L/L_0), which is inferred from
the solution of the Kosterlitz renormalization group equation. The validity of
the Kosterlitz-Thouless theory for this model is confirmed.Comment: 4 pages, 3 figure
SU(N) Heisenberg model with multi-column representations
The symmetric antiferromagnetic Heisenberg model with
multi-column representations on the two-dimensional square lattice is
investigated by quantum Monte Carlo simulations. For the representation of
Young diagram with two columns, we confirm that a valence-bond solid order
appears as soon as the N\'eel order disappears at indicating no
intermediate phase. In the case of the representation with three columns, there
is no evidence for both of the N\'eel and the valence-bond solid ordering for
. This is actually consistent with the large- theory, which
predicts that the VBS state immediately follows the N\'eel state, because the
expected spontaneous order is too weak to be detected.Comment: 5 pages, 5 figure
Entropy Governed by the Absorbing State of Directed Percolation
We investigate the informational aspect of (1+1)-dimensional directed
percolation, a canonical model of a nonequilibrium continuous transition to a
phase dominated by a single special state called the "absorbing" state. Using a
tensor network scheme, we numerically calculate the time evolution of state
probability distribution of directed percolation. We find a universal
relaxation of Renyi entropy at the absorbing phase transition point as well as
a new singularity in the active phase, slightly but distinctly away from the
absorbing transition point. At the new singular point, the second-order Renyi
entropy has a clear cusp. There we also detect a singular behavior of
"entanglement entropy," defined by regarding the probability distribution as a
wave function. The entanglement entropy vanishes below the singular point and
stays finite above. We confirm that the absorbing state, though its occurrence
is exponentially rare in the active phase, is responsible for these phenomena.
This interpretation provides us with a unified understanding of time evolution
of the Renyi entropy at the critical point as well as in the active phase.Comment: 8(=4+4)pages, 13(=5+6) figure
FOREVER22: Gas and metal outflow from massive galaxies in protocluster regions
We study gas and metal outflow from massive galaxies in protocluster regions
at by using the results of the FOREVER22 simulation project. Our
simulations contain massive haloes with , showing high star formation rates of
and hosting supermassive black holes with . We show that the mass loading factor () sensitively
depends on the halo mass and it is for . Once the halo mass exceeds , the outflow velocity of the gas rapidly decreases
near a virial radius, and the gas returns to a galactic centre finally as a
fountain flow. Also, the metal inflow and outflow rates sensitively depend on
the halo mass and redshift. At , the inflow rate becomes larger than the
outflow one if . Thus, we suggest
that massive haloes cannot be efficient metal enrichment sources beyond virial
radii that will be probed in future observations, e.g., studies of metal
absorption lines with the Prime Focus Spectrograph on the Subaru telescope.Comment: 13 pages, 10 figures, accepted for publication in MNRA
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