384 research outputs found
Reconsideration of the QCD corrections to the decays into light hadrons using the principle of maximum conformality
In the paper, we analyze the decays into light hadrons at the
next-to-leading order QCD corrections by applying the principle of maximum
conformality (PMC). The relativistic correction at the -order level has been included in the discussion, which gives about
contribution to the ratio . The PMC, which satisfies the renormalization
group invariance, is designed to obtain a scale-fixed and scheme-independent
prediction at any fixed order. To avoid the confusion of treating -terms,
we transform the usual pQCD series into the one under the
minimal momentum space subtraction scheme. To compare with the prediction under
conventional scale setting, , after applying the PMC, we obtain
, where the
errors are squared averages of the ones caused by and . The PMC prediction agrees with the recent PDG value within errors, i.e.
. Thus we think the mismatching
of the prediction under conventional scale-setting with the data is due to
improper choice of scale, which however can be solved by using the PMC.Comment: 5 pages, 2 figure
Theory and application of Fermi pseudo-potential in one dimension
The theory of interaction at one point is developed for the one-dimensional
Schrodinger equation. In analog with the three-dimensional case, the resulting
interaction is referred to as the Fermi pseudo-potential. The dominant feature
of this one-dimensional problem comes from the fact that the real line becomes
disconnected when one point is removed. The general interaction at one point is
found to be the sum of three terms, the well-known delta-function potential and
two Fermi pseudo-potentials, one odd under space reflection and the other even.
The odd one gives the proper interpretation for the delta'(x) potential, while
the even one is unexpected and more interesting. Among the many applications of
these Fermi pseudo-potentials, the simplest one is described. It consists of a
superposition of the delta-function potential and the even pseudo-potential
applied to two-channel scattering. This simplest application leads to a model
of the quantum memory, an essential component of any quantum computer.Comment: RevTeX4, 32 pages, no figure
Extending the Predictive Power of Perturbative QCD
The predictive power of perturbative QCD (pQCD) depends on two important
issues: (1) how to eliminate the renormalization scheme-and-scale ambiguities
at fixed order, and (2) how to reliably estimate the contributions of unknown
higher-order terms using information from the known pQCD series. The Principle
of Maximum Conformality (PMC) satisfies all of the principles of the
renormalization group and eliminates the scheme-and-scale ambiguities by the
recursive use of the renormalization group equation to determine the scale of
the QCD running coupling at each order. Moreover, the resulting PMC
predictions are independent of the choice of the renormalization scheme,
satisfying the key principle of renormalization group invariance. In this
letter, we show that by using the conformal series derived using the PMC
single-scale procedure, in combination with the Pad\'e Approximation Approach
(PAA), one can achieve quantitatively useful estimates for the unknown
higher-order terms from the known perturbative series. We illustrate this
procedure for three hadronic observables , , and
which are each known to 4 loops in pQCD. We show that
if the PMC prediction for the conformal series for an observable (of leading
order ) has been determined at order , then the
Pad\'e series provides quantitatively useful predictions for
the higher-order terms. We also show that the PMC + PAA predictions agree at
all orders with the fundamental, scheme-independent Generalized Crewther
relations which connect observables, such as deep inelastic neutrino-nucleon
scattering, to hadronic annihilation. Thus, by using the combination
of the PMC series and the Pad\'e method, the predictive power of pQCD theory
can be greatly improved.Comment: 7 pages, 1 figure. Discussions improved and references update
Stage-Specific Expression of TNFα Regulates Bad/Bid-Mediated Apoptosis and RIP1/ROS-Mediated Secondary Necrosis in Birnavirus-Infected Fish Cells
Infectious pancreatic necrosis virus (IPNV) can induce Bad-mediated apoptosis followed by secondary necrosis in fish cells, but it is not known how these two types of cell death are regulated by IPNV. We found that IPNV infection can regulate Bad/Bid-mediated apoptotic and Rip1/ROS-mediated necrotic death pathways via the up-regulation of TNFα in zebrafish ZF4 cells. Using a DNA microarray and quantitative RT-PCR analyses, two major subsets of differentially expressed genes were characterized, including the innate immune response gene TNFα and the pro-apoptotic genes Bad and Bid. In the early replication stage (0–6 h post-infection, or p.i.), we observed that the pro-inflammatory cytokine TNFα underwent a rapid six-fold induction. Then, during the early-middle replication stages (6–12 h p.i.), TNFα level was eight-fold induction and the pro-apoptotic Bcl-2 family members Bad and Bid were up-regulated. Furthermore, specific inhibitors of TNFα expression (AG-126 or TNFα-specific siRNA) were used to block apoptotic and necrotic death signaling during the early or early-middle stages of IPNV infection. Inhibition of TNFα expression dramatically reduced the Bad/Bid-mediated apoptotic and Rip1/ROS-mediated necrotic cell death pathways and rescued host cell viability. Moreover, we used Rip1-specific inhibitors (Nec-1 and Rip1-specific siRNA) to block Rip1 expression. The Rip1/ROS-mediated secondary necrotic pathway appeared to be reduced in IPNV-infected fish cells during the middle-late stage of infection (12–18 h p.i.). Taken together, our results indicate that IPNV triggers two death pathways via up-stream induction of the pro-inflammatory cytokine TNFα, and these results may provide new insights into the pathogenesis of RNA viruses
SDSS J013127.34032100.1: A newly discovered radio-loud quasar at with extremely high luminosity
Only very few z>5 quasars discovered to date are radio-loud, with a
radio-to-optical flux ratio (radio-loudness parameter) higher than 10. Here we
report the discovery of an optically luminous radio-loud quasar, SDSS
J013127.34-032100.1 (J0131-0321 in short), at z=5.18+-0.01 using the Lijiang
2.4m and Magellan telescopes. J0131-0321 has a spectral energy distribution
consistent with that of radio-loud quasars. With an i-band magnitude of 18.47
and radio flux density of 33 mJy, its radio-loudness parameter is ~100. The
optical and near-infrared spectra taken by Magellan enable us to estimate its
bolometric luminosity to be L_bol ~ 1.1E48 erg/s, approximately 4.5 times
greater than that of the most distant quasar known to date. The black hole mass
of J0131-0321 is estimated to be 2.7E9 solar masses, with an uncertainty up to
0.4 dex. Detailed physical properties of this high-redshift, radio-loud,
potentially super-Eddington quasar can be probed in the future with more
dedicated and intensive follow-up observations using multi-wavelength
facilities.Comment: 5 pages, 3 figures, accepted to ApJ
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