309 research outputs found
Multiple critical gravitational collapse of charged scalar with reflecting wall
In this paper, we present the results on the gravitational collapse of
charged massless scalar field in asymptotically flat spacetime with a perfectly
reflecting wall. Differing from previous works, we study the system in the
double null coordinates, by which we could simulate the system until the black
hole forms with higher precision but less performance time. We investigate the
influence of charge on the black hole formation and the scaling behavior near
the critical collapses. The gapless and gapped critical behaviors for black
hole mass and charge are studied numerically. We find that they satisfy the
scaling laws for critical gravitational collapse but the gapped critical
behavior is different from its AdS counterpart.Comment: 12 pages,8 figure
Search for doubly heavy baryon via weak decays
Using the factorization approach and taking into account the final state
interaction, we calculate the two body non-leptonic decays of doubly heavy
baryons. After comparing the semi-leptonic decays and all possible hadronic
decay channels, we found some channels with large branching ratios. Taking the
detection efficiency into consideration, we suggest as the
first search goal and and
as the golden discovery channels with
reconstructed by and ,
respectively.Comment: 4 pages; to appear in the Proceedings of the 53rd Rencontres de
Moriond QCD session of March 201
Coexistence and competition of ferromagnetism and p-wave superconductivity in holographic model
By combining a holographic p-wave superconductor model and a holographic
ferromagnetism model, we study the coexistence and competition of
ferromagnetism and p-wave superconductivity. It is found that the results
depend on the self-interaction of magnetic moment of the complex vector field
and which phase appears first. In the case that the ferromagnetic phase appears
first, if the interaction is attractive, the system shows the ferromagnetism
and superconductivity can coexist in low temperatures. If the interaction is
repulsive, the system will only be in a pure ferromagnetic state. In the case
that the superconducting phase appears first, the attractive interaction will
leads to a magnetic p-wave superconducting phase in low temperatures. If the
interaction is repulsive, the system will be in a pure p-wave superconducting
phase or ferromagnetic phase when the temperature is lowered.Comment: improved version, added some references and background knowledge
Understanding strongly coupling magnetism from holographic duality
The unusual magnetic materials are significant in both science and
technology. However, because of the strongly correlated effects, it is
difficult to understand their novel properties from theoretical aspects.
Holographic duality offers a new approach to understanding such systems from
gravity side. This paper will give a brief review of our recent works on the
applications of holographic duality in understanding unusual magnetic
materials. Some quantitative compare between holographic results and
experimental data will be shown and some predictions from holographic duality
models will be discussed.Comment: For Second LeCosPA Symposium at Taiwan National University, Taipai,
Dec. 14-18, 201
A Holographic Model for Paramagnetism/antiferromagnetism Phase Transition
In this paper we build a holographic model of
paramagnetism/antiferromagnetism phase transition, which is realized by
introducing two real antisymmetric tensor fields coupling to the background
gauge field strength and interacting with each other in a dyonic black brane
background. In the case without external magnetic field and in low
temperatures, the magnetic moments condense spontaneously in antiparallel
manner with the same magnitude and the time reversal symmetry is also broken
spontaneously (if boundary spatial dimension is more than 2, spatial rotational
symmetry is broken spontaneously as well), which leads to an antiferromagnetic
phase. In the case with weak external magnetic field, the magnetic
susceptibility density has a peak at the critical temperature and satisfies the
Curie-Weiss law in the paramagnetic phase of antiferromagnetism. In the strong
external magnetic field case, there is a critical magnetic field in
antiferromagnetic phase: when magnetic field reaches , the system will
return into the paramagnetic phase by a second order phase transition.Comment: The version published in PR
Insulator/metal phase transition and colossal magnetoresistance in holographic model
Within massive gravity, we construct a gravity dual for insulator/metal phase
transition and colossal magnetoresistance (CMR) effect found in some manganese
oxides materials. In heavy graviton limit, a remarkable
magnetic-field-sensitive DC resistivity peak appears at the Curie temperature,
where an insulator/metal phase transition happens and the magnetoresistance is
scaled with the square of field-induced magnetization. We find that metallic
and insulating phases coexist below the Curie point and the relation with the
electronic phase separation is discussed.Comment: Use massive gravity and consider reaction on the geometr
Scaling Laws in Gravitational Collapse
This paper presents two interesting scaling laws, which relate some critical
exponents in the critical behavior of spherically symmetric gravitational
collapses. These scaling laws are independent of the details of gravity theory
under consideration and share similar forms as those in thermodynamic and
geometrical phase transitions in condensed matter system. The properties of the
scaling laws are discussed and some numerical checks are given.Comment: 5 pages, 1 figur
Paramagnetism-Ferromagnetism Phase Transition in a Dyonic Black Hole
Coupling an antisymmetric tensor field to the electromagnetic field in a
dyonic Reissner-Nordstr\"om-AdS black hole background, we build a holographic
model for the paramagnetism/ferromagnetism phase transition. In the case of
zero magnetic field, the time reversal symmetry is broken spontaneously and
spontaneous magnetization happens in low temperature. The critical exponents
are in agreement with the ones from mean field theory. In the case of nonzero
magnetic field, the model realizes the hysteresis loop of single magnetic
domain and the magnetic susceptibility satisfies the Curie-Weiss law.Comment: To appear in PRD as a rapid communicatio
Multi-horizon and Critical Behavior in Gravitational Collapse of Massless Scalar
This paper studies the whole process of gravitational collapse and accretion
of a massless scalar field in asymptotically flat spacetime. Two kinds of
initial configurations are considered. One is the initial data without black
hole, the other contains a black hole. Under suitable initial conditions, we
find that multi-horizon will appear, which means that the initial black hole
formed by gravitational collapse or existing at the beginning will instantly
expand and suddenly grow, rather than grows gradually in the accretion process.
A new type of critical behavior is found around the instant expansion. The
numerical computation shows that the critical exponents are universal.Comment: 5 pages, 3 figure
Radiative charmless B_{(s)}\to V \gamma and B_{(s)}\to A \gamma decays in pQCD approach
We study the radiative charmless decays in
perturbative QCD (pQCD) approach to the leading order in (here
and denotes vector mesons and two kinds of axial-vector mesons: and
states, respectively.). Our predictions of branching ratios are
consistent with the current available experimental data. We update all
form factors and give the predictions for form factors
using the recent hadronic inputs. In addition to the dominant factorizable
spectator diagrams, which is form factor like, we also calculate the so-called
``power suppressed'' annihilation type diagrams, the gluonic penguin, charming
penguin, and two photon diagrams. These diagrams give the main contributions to
direct CP asymmetries, mixing-induced CP asymmetry variables, the isospin
asymmetry and U-spin asymmetry variables. Unlike the branching ratios, these
ratios or observables possess higher theoretical precision in our pQCD
calculation, since they do not depend on the input hadronic parameters too
much. Most of the results still need experimental tests in the on-going and
forthcoming experiments.Comment: 54 pages, 9 figures. Typos are corrected and more references are
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