2,436 research outputs found
Quantum phase transitions in coupled two-level atoms in a single-mode cavity
The dipole-coupled two-level atoms(qubits) in a single-mode resonant cavity
is studied by extended bosonic coherent states. The numerically exact solution
is presented. For finite systems, the first-order quantum phase transitions
occur at the strong interatomic interaction. Similar to the original Dicke
model, this system exhibits a second-order quantum phase transition from the
normal to the superradiant phases. Finite-size scaling for several observables,
such as the average fidelity susceptibility, the order parameter, and
concurrence are performed for different interatomic interactions. The obtained
scaling exponents suggest that interatomic interactions do not change the
universality class.Comment: 13 pages, 5 figure
BLISTER-regulated vegetative growth is dependent on the protein kinase domain of ER stress modulator IRE1A in Arabidopsis thaliana
The unfolded protein response (UPR) is required for protein homeostasis in the endoplasmic reticulum (ER) when plants are challenged by adverse environmental conditions. Inositol-requiring enzyme 1 (IRE1), the bifunctional protein kinase / ribonuclease, is an important UPR regulator in plants mediating cytoplasmic splicing of the mRNA encoding the transcription factor bZIP60. This activates the UPR signaling pathway and regulates canonical UPR genes. However, how the protein activity of IRE1 is controlled during plant growth and development is largely unknown. In the present study, we demonstrate that the nuclear and Golgi-localized protein BLISTER (BLI) negatively controls the activity of IRE1A/IRE1B under normal growth condition in Arabidopsis. Loss-of-function mutation of BLI results in chronic up-regulation of a set of both canonical UPR genes and non-canonical UPR downstream genes, leading to cell death and growth retardation. Genetic analysis indicates that BLI-regulated vegetative growth phenotype is dependent on IRE1A/IRE1B but not their canonical splicing target bZIP60. Genetic complementation with mutation analysis suggests that the D570/K572 residues in the ATP-binding pocket and N780 residue in the RNase domain of IRE1A are required for the activation of canonical UPR gene expression, in contrast, the D570/K572 residues and D590 residue in the protein kinase domain of IRE1A are important for the induction of non-canonical UPR downstream genes in the BLI mutant background, which correlates with the shoot growth phenotype. Hence, our results reveal the important role of IRE1A in plant growth and development, and BLI negatively controls IRE1A’s function under normal growth condition in plants
Phase diagram and exotic spin-spin correlations of anisotropic Ising model on the Sierpi\'nski gasket
The anisotropic antiferromagnetic Ising model on the fractal Sierpi\'{n}ski
gasket is intensively studied, and a number of exotic properties are disclosed.
The ground state phase diagram in the plane of magnetic field-interaction of
the system is obtained. The thermodynamic properties of the three plateau
phases are probed by exploring the temperature-dependence of magnetization,
specific heat, susceptibility and spin-spin correlations. No phase transitions
are observed in this model. In the absence of a magnetic field, the unusual
temperature dependence of the spin correlation length is obtained with JJ, and an interesting crossover behavior between different
phases at JJ is unveiled, whose dynamics can be described by the
JJ-dependence of the specific heat, susceptibility and spin
correlation functions. The exotic spin-spin correlation patterns that share the
same special rotational symmetry as that of the Sierpi\'{n}ski gasket are
obtained in both the plateau disordered phase and the plateau
partially ordered ferrimagnetic phase. Moreover, a quantum scheme is formulated
to study the thermodynamics of the fractal Sierpi\'{n}ski gasket with
Heisenberg interactions. We find that the unusual temperature dependence of the
correlation length remains intact in a small quantum fluctuation.Comment: 9 pages, 12 figure
A Possibility of Search for New Physics at LHCb
It is interesting to search for new physics beyond the standard model at
LHCb. We suggest that weak decays of doubly charmed baryon such as
to charmless final states would be a possible
signal for new physics. In this work, we consider two models, i.e. the
unparticle and as examples to study such possibilities. We also discuss
the cases for which have not been observed yet, but
one can expect to find them when LHCb begins running. Our numerical results
show that these two models cannot result in sufficiently large decay widths,
therefore if such modes are observed at LHCb, there must be a new physics other
than the unparticle or models.Comment: 7 pages, 3 figures, 1 table. More references and discussion adde
Accurate numerical solution to the finite-size Dicke model
By using extended bosonic coherent states, a new technique to solve the Dicke
model exactly is proposed in the numerical sense. The accessible system size is
two orders of magnitude higher than that reported in literature. Finite-size
scaling for several observables, such as the ground-state energy, Berry phase,
and concurrence are analyzed. The existing discrepancy for the scaling exponent
of the concurrence is reconciled.Comment: 4 pages, 5 figures. Phys. Rev. A (in press, a Rapid Communication
- …