9,134 research outputs found
News on PHOTOS Monte Carlo: gamma^* -> pi^+ pi^-(gamma) and K^\pm -> pi^+ pi^- e^\pm nu (gamma)
PHOTOS Monte Carlo is widely used for simulating QED effects in decay of
intermediate particles and resonances. It can be easily connected to other main
process generators. In this paper we consider decaying processes gamma^* ->
pi^+ pi^-(gamma) and K^\pm -> pi^+ pi^- e^\pm nu (gamma) in the framework of
Scalar QED. These two processes are interesting not only for the technical
aspect of PHOTOS Monte Carlo, but also for precision measurement of
alpha_{QED}(M_Z), g-2, as well as pi pi scattering lengths.Comment: 6 pages, 11 figures, proceedings of the PhiPsi09, Oct. 13-16, 2009,
Beijing, Chin
Weak Gravity Conjecture for the Effective Field Theories with N Species
We conjecture an intrinsic UV cutoff for the validity of the effective field
theory with a large number of species coupled to gravity. In four dimensions
such a UV cutoff takes the form for scalar
fields with the same potential , . This conjecture
implies that the assisted chaotic inflation or N-flation might be in the
swampland, not in the landscape. Similarly a UV cutoff
is conjectured for the U(1) gauge theory with species.Comment: 12 pages; refs added and some statements clarifie
Observing the Dark Scalar Doublet and its Impact on the Standard-Model Higgs Boson at Colliders
If the Standard Model of particle interactions is extended to include a
second scalar doublet , which is odd under an
unbroken Z_{2} discrete symmetry, it may be called the scalar doublet,
because its lightest neutral member, say H^{0}, is one posssible component for
the dark matter of the Universe. We discuss the general phenomenology of the
four particles of this doublet, without assuming that H^{0} is the dominant
source of dark matter. We also consider the impact of this scalar
doublet on the phenomenology of the SM Higgs boson h.Comment: PRD versio
Spin-Selective Transport of Electron in DNA Double Helix
The experiment that the high spin selectivity and the length-dependent spin
polarization are observed in double-stranded DNA [Science , 894
(2011)], is elucidated by considering the combination of the spin-orbit
coupling, the environment-induced dephasing, and the helical symmetry. We show
that the spin polarization in double-stranded DNA is significant even in the
case of weak spin-orbit coupling, while no spin polarization appears in
single-stranded DNA. Furthermore, the underlying physical mechanism and the
parameters-dependence of the spin polarization are studied.Comment: 5 pages; 4 figure
Effects of spin imbalance on the electric-field driven quantum dissipationless spin current in -doped Semiconductors
It was proposed recently by Murakami et al. [Science \textbf{301},
1348(2003)] that in a large class of -doped semiconductors, an applied
electric field can drive a quantum dissipationless spin current in the
direction perpendicular to the electric field. In this paper we investigate the
effects of spin imbalance on this intrinsic Hall effect. We show that in
a real sample with boundaries, due to the presence of spin imbalance near the
edges of the sample, the spin Hall conductivity is not a constant but a
sensitively - quantity, and due to this fact, in order to
take the effects of spin imbalance properly into account, a microscopic
calculation of both the quantum dissipationless spin Hall current and the spin
accumulation on an equal footing is thus required. Based on such a microscopic
calculation, a detailed discussion of the effects of spin imbalance on the
intrinsic spin Hall effect in thin slabs of -doped semiconductors are
presented.Comment: 8 pages, 2 figures, An extended version with detailed calculations To
appear in Phys. Rev.
Comment on 'Note on the dog-and-rabbit chase problem in introductory kinematics'
We comment on the recent paper by Yuan Qing-Xin and Du Yin-Xiao (Eur. J.
Phys. 29 (2008) N43-N45).Comment: 2 pages, no figure
Investigating the efficacy of bisphosphonates treatment against multiple myeloma induced bone disease using a computational model
Multiple myeloma (MM)-induced bone disease is mortal for most MM patients. Bisphosphonates are first-line treatment for MM-induced bone disease, since it can inhibit osteoclast activity and the resultant bone resorption by suppressing the differentiation of osteoclast precursors into mature osteoclasts, promoting osteoclast apoptosis and disrupting osteoclast function. However, it is still unclear whether bisphosphonates have an anti-tumour effect. In our previous work, a computational model was built to simulate the pathology of MM-induced bone disease. This paper extends this proposed computational model to investigate the efficacy of bisphosphonates treatment and then clear the controversy of this therapy. The extended model is validated through the good agreement between simulation results and experimental data. The simulation results suggest that bisphosphonates indeed have an anti-tumour effect
Computation of the order low-energy constants with tensor sources
We present the results of calculations of the and order
low-energy constants for the chiral Lagrangian with tensor sources for both two
and three flavors of pseudoscalar mesons. This is a generalization of our
previous work on similar calculations without tensor sources in terms of the
quark self-energy , based on the first principle derivation of the
low-energy effective Lagrangian and computation of the low-energy constants
with some rough approximations. With the help of partial integration and some
epsilon relations, we find that some order operators with tensor sources
appearing in the literature are related to each other. That leaves 98
independent terms for -flavor, 92 terms for three-flavor, and 65 terms for
two-flavor cases. We also find that the odd-intrinsic-parity chiral Lagrangian
with tensor sources cannot independently exist in any order of low-energy
expansion.Comment: 29 page
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