127 research outputs found
Replica Method for Wide Correlators in Gaussian Orthogonal, Unitary And Symplectic Random Matrix Ensembles
We calculate connected correlators in Gaussian orthogonal, unitary and
symplectic random matrix ensembles by the replica method in the 1/N-expansion.
We obtain averaged one-point Green's functions up to the next-to-leading order
O(1/N) and wide two-level correlators up to the first nontrivial order O(1/N^2)
and wide three-level correlators up to the first nontrivial order by
carefully treating fluctuations in saddle-point evaluation.Comment: LaTeX 21 pages, a new result on wide three-level correlators adde
Deformation of a renormalization-group equation applied to infinite-order phase transitions
By adding a linear term to a renormalization-group equation in a system
exhibiting infinite-order phase transitions, asymptotic behavior of running
coupling constants is derived in an algebraic manner. A benefit of this method
is presented explicitly using several examples.Comment: 6 pages, 5 figures, revtex4, typo corrected, references adde
An asymptotic formula for marginal running coupling constants and universality of loglog corrections
Given a two-loop beta function for multiple marginal coupling constants, we
derive an asymptotic formula for the running coupling constants driven to an
infrared fixed point. It can play an important role in universal loglog
corrections to physical quantities.Comment: 16 pages; typos fixed, one appendix removed for quick access to the
main result; to be published in J. Phys.
Stability of fixed points in the (4+\epsilon)-dimensional random field O(N) spin model for sufficiently large N
We study the stability of fixed points in the two-loop renormalization group
for the random field O() spin model in dimensions. We solve the
fixed-point equation in the 1/N expansion and expansion. In the
large-N limit, we study the stability of all fixed points. We solve the
eigenvalue equation for the infinitesimal deviation from the fixed points under
physical conditions on the random anisotropy function. We find that the fixed
point corresponding to dimensional reduction is singly unstable and others are
unstable or unphysical. Therefore, one has no choice other than dimensional
reduction in the large-N limit. The two-loop function enables us to
find a compact area in the plane where the dimensional reduction
breaks down. We calculate higher-order corrections in the 1/N and
expansions to the fixed point. Solving the corrected eigenvalue equation
nonperturbatively, we find that this fixed point is singly unstable also for
sufficiently large and the critical exponents show a dimensional reduction.Comment: 9 pages, 2 figure
A variability study of the Seyfert 2 galaxy NGC 6300 with XMM-Newton
We present the results of timing analysis of the XMM-Newton observation of
the Seyfert 2 galaxy NGC 6300. The hard X-ray spectrum above 2 keV consists of
a Compton-thin-absorbed power law, as is often seen in Seyfert 2 galaxies. We
clearly detected rapid time variability on a time scale of about 1000 s from
the light curve above 2 keV. The excess variance of the time variability
(sigma2_RMS) is calculated to be ~0.12, and the periodogram of the light curve
is well represented by a power law function with a slope of 1.75. In contrast
with previous results from Seyfert 2 nuclei, these variability characteristics
are consistent with those of Seyfert 1 galaxies. This consistency suggests that
NGC 6300 has a similar black hole mass and accretion properties as Seyfert 1
galaxies. Using the relation between time variability and central black hole
mass by Hayashida et al. (1998), the black hole mass of NGC 6300 is estimated
to be ~2.8x10^5 Mo. Taking uncertainty of this method into account, the black
hole mass is less than 10^7 Mo. Taking the bolometric luminosity of 3.3x10^43
erg/s into consideration, this yields an accretion rate of > 0.03 of the
Eddington value, and comparable with estimates from Seyfert 1 galaxies using
this method. The time variability analysis suggests that NGC 6300 actually has
a Seyfert 1 nucleus obscured by a thick matter, and more generally provides a
new pillar of support for the unified model of Seyfert galaxies based on
obscuration.Comment: 11 pages, 6 figures, accepted for publication in Ap
Suppressive effects of co-stimulatory molecule expressions on mouse splenocytes by anti-allergic agents in vitro.
The influence of anti-allergic drugs, epinastine hydrochloride (EP) and disodium cromoglycate (DSCG), on the co-stimulatory molecule expression was examined using in vitro cell culture technique. Spleen cells obtained from BALB/c mice 10 days after immunization with haemocyanin absorbed to aluminium hydroxide were cultured in the presence of 100.0 microg/ml haemocyanin and various concentrations of the agents. Low concentrations (<1.5 x 10(-4)M) of EP and DSCG did not influence spleen cell blastic activity induced by antigenic stimulation, whereas these agents caused significant inhibition of spleen cell activation when 2 x 10(-4) M of the agents were added to cell cultures. EP and DSCG also did not affect blastic activity of sensitized splenic T cells by anti-CD3 monoclonal antibody stimulation even when these cells were cultured in the presence of 2 x 10(-4) M of the agents. We next examined the influence of EP and DSCG on the expression of co-stimulatory molecules on spleen cells in response to antigenic stimulation. Sensitized spleen cells were cultured in the presence of 2 x 10(-4)M of the agents and the expression of molecules were examined by flow cytometer 24h later. EP and DSCG suppressed the expression of costimulatory molecules, CD40 and CD80, but not CD86, on splenic B cells which were enhanced by antigenic stimulation in vitro
The hardest X-ray source in the ASCA Large Sky Survey: Discovery of a new type 2 Seyfert
We present results of ASCA deep exposure observations of the hardest X-ray
source discovered in the ASCA Large Sky Survey (LSS) project, designated as AX
J131501+3141. We extract its accurate X-ray spectrum, taking account of the
contamination from a nearby soft source (AX J131502+3142), separated only by
1'. AX J131501+3141 exhibits a large absorption of NH = (6 +4 -2)x 10^22 H/cm^2
with a photon index \Gamma = 1.5 +0.7 -0.6. The 2--10 keV flux was about 5 x
10^-13 erg/s/cm^2 and was time variable by a factor of 30% in 0.5 year. From
the highly absorbed X-ray spectrum and the time variability, as well as the
results of the optical follow-up observations (Akiyama et al. 1998,
astro-ph/9801173), we conclude that AX J131501+3141 is a type 2 Seyfert galaxy.
Discovery of such a low flux and highly absorbed X-ray source could have a
significant impact on the origin of the cosmic X-ray background.Comment: 16 pages, 6 figures, requires AAS Latex macro v4.0, to appear in The
Astrophysical Journal, text and figures also available at
http://www-cr.scphys.kyoto-u.ac.jp/member/sakano/work/paper/index-e.htm
NGC 7582: The Prototype Narrow-Line X-ray Galaxy
NGC 7582 is a candidate prototype of the Narrow Line X-ray Galaxies (NLXGs)
found in deep X-ray surveys. An ASCA observation shows the hard (> 3 keV) X-ray
continuum of NGC 7582 drops 40% in ~6 ks, implying an AGN, while the soft band
(< 3 keV) does not drop in concert with the hard continuum, requiring a
separate component. The X-ray spectrum of NGC 7582 also shows a clear 0.5-2 keV
soft (kT = 0.8 (+0.9,-0.3) keV or Gamma = 2.4 +/- 0.6; L(X) = 6 x 10**40 ergs
s**-1) low--energy component, in addition to a heavily absorbed [N(H) = (6 +/-
2)\times 10**22 cm**-2 ] and variable 2-10 keV power law [Gamma = 0.7
(+0.3,-0.4); L(X) = (1.7-2.3) x 10**42 ergs s**-1]. This is one of the flattest
2-10 keV slopes in any AGN observed with ASCA. (The ROSAT HRI image of NGC 7582
further suggests extent to the SE.)
These observations make it clear that the hard X-ray emission of NGC 7582,
the most "narrow-line" of the NLXGs, is associated with an AGN. The strong
suggestion is that all NLXGs are obscured AGNs, as hypothesized to explain the
X-ray background spectral paradox. The separate soft X-ray component makes NGC
7582 (and by extension other NLXGs) detectable as a ROSAT source.Comment: text: Latex2e 10 pages, including 1 table, and 2 postscript figures
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