4,604 research outputs found
Two Particle States in a Box and the -Matrix in Multi-Channel Scattering
Using a quantum mechanical model, the exact energy eigenstates for
two-particle two-channel scattering are studied in a cubic box with periodic
boundary conditions.
A relation between the exact energy eigenvalue in the box and the two-channel
-matrix elements in the continuum is obtained. This result can be viewed as
a generalization of the well-known L\"uscher's formula which establishes a
similar relation in elastic scattering.Comment: 4 pages, typeset with ws-ijmpa.cls. Talk presented at International
Conference on QCD and Hadronic Physics, June 16-20, 2005, Beijing, China. One
reference adde
Massive Overlap Fermions on Anisotropic Lattices
We formulate the massive overlap fermions on anisotropic lattices.
We find that the dispersion relation for the overlap fermion resembles the
continuum form in the low-momentum region once the bare parameters are properly
tuned. The quark self-energy and the quark field renormalization constants are
calculated to one-loop in bare lattice perturbation theory.
We argue that massive domain wall quarks might be helpful in lattice QCD
studies on heavy-light hadron spectroscopy.Comment: 21 pages, 5 figures, one reference added compared with v.
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Regulations on Biotechnological Research and Biologically Modified Products
The developments in biotechnology have brought not only benefits but also harms to society. On the one hand, the biotechnologically modified products has rapidly changed our lifestyle, but on the other hand, they could also endanger the ecosystem due to their reproduction and novel characteristics, and raise sharp debate over social values, including moral and religious values, and ethical standards. These rapid developments and problems of biotechnology posed a significant challenge to policymakers. E.g., are current regulations enough? Or do we need more regulations for biotechnological experiments and the development of genetically modified products because of their potential negative impacts? After comparing the advantages (such as the avoidance of the negative and special influences of biotechnology, and the solution of market failure and social injustice) and disadvantages (such as economic loss, government failure, and violation of social justice and freedom of scientific experiments), this research addressed that more and specified regulations are necessary. However, the scope of regulations ¡V or how much control the government should have in scientific development ¡V should be reasonably limited to give consideration to the independence of scientific fields, and economic developments. First, the regulations of biotechnological experiments should be looser than those of genetically modified products because of the different substantial impacts on consumers, and the respect of the freedom of speech (or research). Second, more participation of the general public will help to avoid the professionals¡¦ and governments¡¦ arbitrary decisions. Third, the regulations of ¡§Physical Risks¡¨ and ¡§Social Risks and Ethical Considerations¡¨ should be different because their influences are varified
Scaling of geometric phase versus band structure in cluster-Ising models
We study the phase diagram of a class of models in which a generalized
cluster interaction can be quenched by Ising exchange interaction and external
magnetic field. We characterize the various phases through winding numbers.
They may be ordinary phases with local order parameter or exotic ones, known as
symmetry protected topologically ordered phases. Quantum phase transitions with
dynamical critical exponents z = 1 or z = 2 are found. Quantum phase
transitions are analyzed through finite-size scaling of the geometric phase
accumulated when the spins of the lattice perform an adiabatic precession. In
particular, we quantify the scaling behavior of the geometric phase in relation
with the topology and low energy properties of the band structure of the
system
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