882 research outputs found
Discrete Symmetries (C,P,T) in Noncommutative Field Theories
In this paper we study the invariance of the noncmmutative gauge theories
under C, P and T transformations. For the noncommutative space (when only the
spatial part of is non-zero) we show that NCQED is Parity invariant.
In addition, we show that under charge conjugation the theory on noncommutative
is transformed to the theory on , so NCQED is a
CP violating theory. The theory remains invariant under time reversal if,
together with proper changes in fields, we also change by .
Hence altogether NCQED is CPT invariant. Moreover we show that the CPT
invariance holds for general noncommutative space-time.Comment: Revtex File, 4 pages, no figures, minor changes from previous verion.
To appear in Phys. Rev. Let
Mean-field and direct numerical simulations of magnetic flux concentrations from vertical field
Strongly stratified hydromagnetic turbulence has previously been found to
produce magnetic flux concentrations if the domain is large enough compared
with the size of turbulent eddies. Mean-field simulations (MFS) using
parameterizations of the Reynolds and Maxwell stresses show a negative
effective magnetic pressure instability and have been able to reproduce many
aspects of direct numerical simulations (DNS) regarding the growth rate of this
large-scale instability, shape of the resulting magnetic structures, and their
height as a function of magnetic field strength. Unlike the case of an imposed
horizontal field, for a vertical one, magnetic flux concentrations of
equipartition strength with the turbulence can be reached. This results in
magnetic spots that are reminiscent of sunspots. Here we want to find out under
what conditions magnetic flux concentrations with vertical field occur and what
their internal structure is. We use a combination of MFS, DNS, and implicit
large-eddy simulations to characterize the resulting magnetic flux
concentrations in forced isothermal turbulence with an imposed vertical
magnetic field. We confirm earlier results that in the kinematic stage of the
large-scale instability the horizontal wavelength of structures is about 10
times the density scale height. At later times, even larger structures are
being produced in a fashion similar to inverse spectral transfer in helically
driven turbulence. Using turbulence simulations, we find that magnetic flux
concentrations occur for different values of the Mach number between 0.1 and
0.7. DNS and MFS show magnetic flux tubes with mean-field energies comparable
to the turbulent kinetic energy. The resulting vertical magnetic flux tubes are
being confined by downflows along the tubes and corresponding inflow from the
sides, which keep the field concentrated.Comment: 16 pages, 22 figures, Astron. Astrophys., in pres
Nearing Extremal Intersecting Giants and New Decoupled Sectors in N = 4 SYM
We study near-horizon limits of near-extremal charged black hole solutions to
five-dimensional gauged supergravity carrying two charges, extending
the recent work of Balasubramanian et.al. We show that there are two
near-horizon decoupling limits for the near-extremal black holes, one
corresponding to the near-BPS case and the other for the far from BPS case.
Both of these limits are only defined on the 10d IIB uplift of the 5d black
holes, resulting in a decoupled geometry with a six-dimensional part (conformal
to) a rotating BTZ X . We study various aspects of these decoupling limits
both from the gravity side and the dual field theory side. For the latter we
argue that there should be two different, but equivalent, dual gauge theory
descriptions, one in terms of the 2d CFT's dual to the rotating BTZ and the
other as certain large R-charge sectors of d=4,N =4 U(N) SYM theory. We discuss
new BMN-type sectors of the N=4 SYM in the limit in which the
engineering dimensions scale as (for the near-BPS case) and as
(for the far from BPS case).Comment: 44 pages, references added, minor change
Serum lactate as a prognostic factor in coronary artery bypass graft operation by on pump method
Background: Lactic acidosis in cardiac surgical patients is a manifestation of systemic inflammation and excess pro-inflammatory cytokine production. This investigation was designed to integrate basic concepts about lactate acidosis with a clinically used of serum lactate in patients under coronary artery bypass surgery (CABG) by on pump method. Methods: From August to September 2012, 15 patients scheduled for routine cardiac surgery entered to our sample and followed up two weeks. Lactate concentration in arterial blood sample was studied. Method of surgery duration of cardiopulmonary bypass, aorta cross clamp timing, hemodynamic parameters, inotrope dosage and patient outcome were documented. The data were collected and analyzed. Results: The mean age of the patients was 62±14 years. The patients with a poor outcome had significantly higher lactate levels in ABG samples (p0.05). The PH of ABG samples did not generally correlate with the ABG lactate concentration (r=0.116, p=0.68). Increased lactate concentration was reliably associated with patient hemodynamic parameters, inotrope dosage, duration of on pump time and aorta cross clamp time. Conclusion: This study demonstrates a correlation between serum lactate levels and patient prognosis after CABG surgery by on pump method
Tensor model and dynamical generation of commutative nonassociative fuzzy spaces
Rank-three tensor model may be regarded as theory of dynamical fuzzy spaces,
because a fuzzy space is defined by a three-index coefficient of the product
between functions on it, f_a*f_b=C_ab^cf_c. In this paper, this previous
proposal is applied to dynamical generation of commutative nonassociative fuzzy
spaces. It is numerically shown that fuzzy flat torus and fuzzy spheres of
various dimensions are classical solutions of the rank-three tensor model.
Since these solutions are obtained for the same coupling constants of the
tensor model, the cosmological constant and the dimensions are not fundamental
but can be regarded as dynamical quantities. The symmetry of the model under
the general linear transformation can be identified with a fuzzy analog of the
general coordinate transformation symmetry in general relativity. This symmetry
of the tensor model is broken at the classical solutions. This feature may make
the model to be a concrete finite setting for applying the old idea of
obtaining gravity as Nambu-Goldstone fields of the spontaneous breaking of the
local translational symmetry.Comment: Adding discussions on effective geometry, a note added, four
references added, other minor changes, 27 pages, 17 figure
Non-Commutative GUTs, Standard Model and C,P,T properties from Seiberg-Witten map
Noncommutative generalizations of Yang-Mills theories using Seiberg-Witten
map are in general not unique. We study these ambiguities and see that SO(10)
GUT, at first order in the noncommutativity parameter \theta, is unique and
therefore is a truly unified theory, while SU(5) is not. We then present the
noncommutative Standard Model compatible with SO(10) GUT. We next study the
reality, hermiticity and C,P,T properties of the Seiberg-Witten map and of
these noncommutative actions at all orders in \theta. This allows to compare
the Standard Model discussed in [5] with the present GUT inspired one.Comment: 9 pages. Presented at the Balkan Workshop 2003, Vrnjacka Banja,
29.8-2.9.2003 and at the 9th Adriatic Meeting, Dubrovnik, 4-14.9.200
A note on bosonic open strings in constant B field
We sketch the main steps of old covariant quantization of bosonic open
strings in a constant field background. We comment on its space-time
symmetries and the induced effective metric. The low-energy spectrum is
evaluated and the appearance of a new non-commutative gauge symmetry is
addressed.Comment: 13 pages, Latex, important comments added, to appear in PR
and colliding in noncommutative space
By studying the scattering process of scalar particle pion on the
noncommutative scalar quantum electrodynamics, the non-commutative amendment of
differential scattering cross-section is found, which is dependent of
polar-angle and the results are significantly different from that in the
commutative scalar quantum electrodynamics, particularly when . The non-commutativity of space is expected to be explored at around
TeV.Comment: Latex, 12 page
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