295 research outputs found
Issues on 3D Noncommutative Electromagnetic Duality
We extend the ordinary 3D electromagnetic duality to the noncommutative (NC)
space-time through a Seiberg-Witten map to second order in the noncommutativity
parameter (theta), defining a new scalar field model. There are similarities
with the 4D NC duality, these are exploited to clarify properties of both
cases. Up to second order in theta, we find that duality interchanges the
2-form theta with its 1-form Hodge dual *theta times the gauge coupling
constant, i.e., theta --> *theta g^2 (similar to the 4D NC electromagnetic
duality). We directly prove that this property is false in the third order
expansion in both 3D and 4D space-times, unless the slowly varying fields limit
is imposed. Outside this limit, starting from the third order expansion, theta
cannot be rescaled to attain an S-duality. In addition to possible applications
on effective models, the 3D space-time is useful for studying general
properties of NC theories. In particular, in this dimension, we deduce an
expression that significantly simplifies the Seiberg-Witten mapped Lagrangian
to all orders in theta.Comment: 15 pages, revtex4. v.2: We added a proof that the terms in (4.9) are
not surface terms, a new paragraph in our conclusion and new references. v.3:
improvements in our introduction and conclusions. v.4: Published version
(PRD): additional comments and reference
Space/time noncommutative field theories and causality
As argued previously, amplitudes of quantum field theories on noncommutative
space and time cannot be computed using naive path integral Feynman rules. One
of the proposals is to use the Gell-Mann--Low formula with time-ordering
applied before performing the integrations. We point out that the previously
given prescription should rather be regarded as an interaction point
time-ordering. Causality is explicitly violated inside the region of
interaction. It is nevertheless a consistent procedure, which seems to be
related to the interaction picture of quantum mechanics. In this framework we
compute the one-loop self-energy for a space/time noncommutative \phi^4 theory.
Although in all intermediate steps only three-momenta play a role, the final
result is manifestly Lorentz covariant and agrees with the naive calculation.
Deriving the Feynman rules for general graphs, we show, however, that such a
picture holds for tadpole lines only.Comment: 16 pages, LaTeX, uses feynmf macros, one reference added; ooops,
version 2 was an older one
Approaches to the low grade metamorphic history of the karakaya complex by chlorite mineralogy and geochemistry
In this study, chlorite is used to investigate the diagenetic-metamorphic evolution and accurate geological history of the different units belonging to the Karakaya complex, Turkey. Primary and secondary chlorite minerals in the very low-grade metamorphic rocks display interference colors of blue and brown and an appearance of optical isotropy. Chlorites are present in the matrix, pores, and/or rocks units as platy/flaky and partly radial forms. X-ray diffraction (XRD) data indicate that Mg-Fe chlorites with entirely IIb polytype (trioctahedral) exhibit a variety of compositions, such as brunsvigite-diabantite-chamosite. The major element contents and structural formulas of chlorite also suggest these were derived from both felsic and metabasic source rocks. Trace and rare earth element (REE) concentrations of chlorites increase with increasing grade of metamorphism, and these geochemical changes can be related to the tectonic structures, formational mechanics, and environments present during their generation. © 2015 by the authors; licensee MDPI, Basel, Switzerland
Trace Anomaly in Quantum Spacetime Manifold
In this paper we investigate the trace anomaly in a spacetime where single
events are de-localized as a consequence of short distance quantum coordinate
fluctuations. We obtain a modified form of heat kernel asymptotic expansion
which does not suffer from short distance divergences. Calculation of the trace
anomaly is performed using an IR regulator in order to circumvent the absence
of UV infinities. The explicit form of the trace anomaly is presented and the
corresponding 2D Polyakov effective action and energy momentumtensor are
obtained. The vacuum expectation value of the energy momentum tensor in the
Boulware, Hartle-Hawking and Unruh vacua is explicitly calculated in a
(rt)-section of a recently found, noncommutative geometry inspired,
Schwarzschild-like solution of the Einstein equations. The standard short
distance divergences in the vacuum expectation values are regularized in
agreement with the absence of UV infinities removed by quantum coordinate
fluctuations.Comment: 15pages, RevTex, no figures, 1 Tabl
On renormalizability of the massless Thirring model
We discuss the renormalizability of the massless Thirring model in terms of
the causal fermion Green functions and correlation functions of left-right
fermion densities. We obtain the most general expressions for the causal
two-point Green function and correlation function of left-right fermion
densities with dynamical dimensions of fermion fields, parameterised by two
parameters. The region of variation of these parameters is constrained by the
positive definiteness of the norms of the wave functions of the states related
to components of the fermion vector current. We show that the dynamical
dimensions of fermion fields calculated for causal Green functions and
correlation functions of left-right fermion densities can be made equal. This
implies the renormalizability of the massless Thirring model in the sense that
the ultra-violet cut-off dependence, appearing in the causal fermion Green
functions and correlation functions of left-right fermion densities, can be
removed by renormalization of the wave function of the massless Thirring
fermion fields only.Comment: 17 pages, Latex, the contribution of fermions with opposite chirality
is added,the parameterisation of fermion determinant by two parameters is
confirmed,it is shown that dynamical dimensions of fermion fields calculated
from different correlation functions can be made equal.This allows to remove
the dependence on the ultra-violet cut-off by the renormalization of the wave
function of Thirring fermion fields onl
Diagenetic history of the rock units of bozkir unit controlled by the triassic rifting, Bozkır-Konya
The Bozkir Unit representing the northern edge of the Taurus Belt. It comprises from bottom to top, three distinct structural entities: the Upper Triassic pre-rift (Korualan Group), the Upper Triassic-Upper Cretaceous syn-rift (Huglu Group) and the Jurassic-Cretaceous Boyali Tepe Group as to their structural settings. The Korualan Group is represented by the alternations of carbonate (limestone, dolomitic limestone, dolomite) with radiolarite and chert intercalations and clastic rocks (sandstone, siltstone, mudstone, shale). The Huglu Group is made up of volcanic (basalt, andesite) and pyroclastic (tuffaceous sandstone) rocks including radyolarite, limestone and clastic rock (sandstone, siltstone, shale) intercalations. The Boyali Tepe Group is completely made of carbonate rocks. The carbonate-silisiclastic-volcanogenic rocks of the Bozkir Unit contain carbonate (calcite, dolomite), quartz, feldspar (plagioclase, anortoclase), phyllosilicate (illite, chlorite, mixed-layered illite-chlorite/I-C, chlorite-vermiculite/C-V, chlorite-smectite/C-S, rarely smectite), augite, hematite, analcime and heulandite in order of abundance. On the basis of illite Kübler Index data; Korualan Group and Huglu Group re?ect low grade diagenetic, high grade diagenetic and high grade diagenetic-anchizonal characteristics, respectively. The illite/micas of the pre-rift units and units related to the rifting have muscovitic, and phengitic and seladonitic compositions, respectively. The distributions of chondrite-normalized trace and rare earth element (REE) contents in the illites present similar trends for Korulan ve Huglu groups, but the quantities of these elements slightly increase in the Huglu Group. δ18O-dD isotopic compositions of water forming the illite minerals are different than that of sea water and found to be between Eastern Mediterranean Meteoric Water (EMMW) and magmatic water compositions. It also shows that temperature of the water forming the illite minerals varies from low to high values. The fndings from the rocks of Bozkir Unit suggest that pre-and syn-rift units have different mineralogical-petrographical and geochemical properties. The younger units within the rift due to extension and crustal thinning related to rifting must have exposed in higher diagenetic conditions by more burial and heat with respect to older units at the edges
Are there Local Minima in the Magnetic Monopole Potential in Compact QED?
We investigate the influence of the granularity of the lattice on the
potential between monopoles. Using the flux definition of monopoles we
introduce their centers of mass and are able to realize continuous shifts of
the monopole positions. We find periodic deviations from the -behavior of
the monopole-antimonopole potential leading to local extrema. We suppose that
these meta-stabilities may influence the order of the phase transition in
compact QED.Comment: 11 pages, 5 figure
On "full" twisted Poincare' symmetry and QFT on Moyal-Weyl spaces
We explore some general consequences of a proper, full enforcement of the
"twisted Poincare'" covariance of Chaichian et al. [14], Wess [50], Koch et al.
[34], Oeckl [41] upon many-particle quantum mechanics and field quantization on
a Moyal-Weyl noncommutative space(time). This entails the associated braided
tensor product with an involutive braiding (or -tensor product in the
parlance of Aschieri et al. [3,4]) prescription for any coordinates pair of
generating two different copies of the space(time); the associated
nontrivial commutation relations between them imply that is central and
its Poincar\'e transformation properties remain undeformed. As a consequence,
in QFT (even with space-time noncommutativity) one can reproduce notions (like
space-like separation, time- and normal-ordering, Wightman or Green's
functions, etc), impose constraints (Wightman axioms), and construct free or
interacting theories which essentially coincide with the undeformed ones, since
the only observable quantities involve coordinate differences. In other words,
one may thus well realize QM and QFT's where the effect of space(time)
noncommutativity amounts to a practically unobservable common noncommutative
translation of all reference frames.Comment: Latex file, 24 pages. Final version to appear in PR
Genome-Wide Transcriptional Reorganization Associated with Senescence-to-Immortality Switch during Human Hepatocellular Carcinogenesis
Cataloged from PDF version of article.Senescence is a permanent proliferation arrest in response to cell stress such as DNA damage. It contributes strongly to tissue aging and serves as a major barrier against tumor development. Most tumor cells are believed to bypass the senescence barrier (become "immortal") by inactivating growth control genes such as TP53 and CDKN2A. They also reactivate telomerase reverse transcriptase. Senescence-to-immortality transition is accompanied by major phenotypic and biochemical changes mediated by genome-wide transcriptional modifications. This appears to happen during hepatocellular carcinoma (HCC) development in patients with liver cirrhosis, however, the accompanying transcriptional changes are virtually unknown. We investigated genome-wide transcriptional changes related to the senescence-to-immortality switch during hepatocellular carcinogenesis. Initially, we performed transcriptome analysis of senescent and immortal clones of Huh7 HCC cell line, and identified genes with significant differential expression to establish a senescence-related gene list. Through the analysis of senescence-related gene expression in different liver tissues we showed that cirrhosis and HCC display expression patterns compatible with senescent and immortal phenotypes, respectively; dysplasia being a transitional state. Gene set enrichment analysis revealed that cirrhosis/senescence-associated genes were preferentially expressed in non-tumor tissues, less malignant tumors, and differentiated or senescent cells. In contrast, HCC/immortality genes were up-regulated in tumor tissues, or more malignant tumors and progenitor cells. In HCC tumors and immortal cells genes involved in DNA repair, cell cycle, telomere extension and branched chain amino acid metabolism were up-regulated, whereas genes involved in cell signaling, as well as in drug, lipid, retinoid and glycolytic metabolism were down-regulated. Based on these distinctive gene expression features we developed a 15-gene hepatocellular immortality signature test that discriminated HCC from cirrhosis with high accuracy. Our findings demonstrate that senescence bypass plays a central role in hepatocellular carcinogenesis engendering systematic changes in the transcription of genes regulating DNA repair, proliferation, differentiation and metabolism
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