19,217 research outputs found
Canonical Quantization of the Self-Dual Model coupled to Fermions
This paper is dedicated to formulate the interaction picture dynamics of the
self-dual field minimally coupled to fermions. To make this possible, we start
by quantizing the free self-dual model by means of the Dirac bracket
quantization procedure. We obtain, as result, that the free self-dual model is
a relativistically invariant quantum field theory whose excitations are
identical to the physical (gauge invariant) excitations of the free
Maxwell-Chern-Simons theory. The model describing the interaction of the
self-dual field minimally coupled to fermions is also quantized through the
Dirac bracket quantization procedure. One of the self-dual field components is
found not to commute, at equal times, with the fermionic fields. Hence, the
formulation of the interaction picture dynamics is only possible after the
elimination of the just mentioned component. This procedure brings, in turns,
two new interaction terms, which are local in space and time while
non-renormalizable by power counting. Relativistic invariance is tested in
connection with the elastic fermion-fermion scattering amplitude. We prove that
all the non-covariant pieces in the interaction Hamiltonian are equivalent to
the covariant minimal interaction of the self-dual field with the fermions. The
high energy behavior of the self-dual field propagator corroborates that the
coupled theory is non-renormalizable. Certainly, the self-dual field minimally
coupled to fermions bears no resemblance with the renormalizable model defined
by the Maxwell-Chern-Simons field minimally coupled to fermions.Comment: 16 pages, no special macros, no corrections in the pape
On the constrained structure of duality symmetric Maxwell theory
The constrained structure of the duality invariant form of Maxwell theory is
considered in the Hamiltonian formulation of Dirac as well as from the
symplectic viewpoint. Compared to the former the latter approach is found to be
more economical and elegant. Distinctions from the constrained analysis of the
usual Maxwell theory are pointed out and their implications are also discussed.Comment: Latex, 12 page
Cointegration in Panel Data with Breaks and Cross-Section Dependence
The power of standard panel cointegration statistics may be affected by misspecification errors if proper account is not taken of the presence of structural breaks in the data. We propose modifications to allow for one structural break when testing the null hypothesis of no cointegration that retain good properties in terms of empirical size and power. Response surfaces to approximate the finite sample moments that are required to implement the statistics are provided. Since panel cointegration statistics rely on the assumption of cross-section independence, a generalisation of the tests to the common factor framework is carried out in order to allow for dependence among the units of the panel.Panel cointegration, structural break, common factors, cross-section dependence
Dual Projection and Selfduality in Three Dimensions
We discuss the notion of duality and selfduality in the context of the dual
projection operation that creates an internal space of potentials. Contrary to
the prevailing algebraic or group theoretical methods, this technique is
applicable to both even and odd dimensions. The role of parity in the kernel of
the Gauss law to determine the dimensional dependence is clarified. We derive
the appropriate invariant actions, discuss the symmetry groups and their proper
generators. In particular, the novel concept of duality symmetry and
selfduality in Maxwell theory in (2+1) dimensions is analysed in details. The
corresponding action is a 3D version of the familiar duality symmetric
electromagnetic theory in 4D. Finally, the duality symmetric actions in the
different dimensions constructed here manifest both the SO(2) and
symmetries, contrary to conventional results.Comment: 20 pages, late
Analysis of regulatory network involved in mechanical induction of embryonic stem cell differentiation
Embryonic stem cells are conventionally differentiated by modulating specific growth factors in the cell culture media. Recently the effect of cellular mechanical microenvironment in inducing phenotype specific differentiation has attracted considerable attention. We have shown the possibility of inducing endoderm differentiation by culturing the stem cells on fibrin substrates of specific stiffness [1]. Here, we analyze the regulatory network involved in such mechanically induced endoderm differentiation under two different experimental configurations of 2-dimensional and 3-dimensional culture, respectively. Mouse embryonic stem cells are differentiated on an array of substrates of varying mechanical properties and analyzed for relevant endoderm markers. The experimental data set is further analyzed for identification of co-regulated transcription factors across different substrate conditions using the technique of bi-clustering. Overlapped bi-clusters are identified following an optimization formulation, which is solved using an evolutionary algorithm. While typically such analysis is performed at the mean value of expression data across experimental repeats, the variability of stem cell systems reduces the confidence on such analysis of mean data. Bootstrapping technique is thus integrated with the bi-clustering algorithm to determine sets of robust bi-clusters, which is found to differ significantly from corresponding bi-clusters at the mean data value. Analysis of robust bi-clusters reveals an overall similar network interaction as has been reported for chemically induced endoderm or endodermal organs but with differences in patterning between 2-dimensional and 3-dimensional culture. Such analysis sheds light on the pathway of stem cell differentiation indicating the prospect of the two culture configurations for further maturation. © 2012 Zhang et al
Health outcomes of children born to mothers with chronic kidney disease: a pilot study
This study aimed to study the health of children born to mothers with chronic kidney disease. Twenty-four children born to mothers with chronic kidney disease were compared with 39 matched control children born to healthy mothers without kidney disease. The well-being of each child was individually assessed in terms of physical health, neurodevelopment and psychological health. Families participating with renal disease were more likely to be from lower socio-economic backgrounds. Significantly fewer vaginal deliveries were reported for mothers with renal disease and their infants were more likely to experience neonatal morbidity. Study and control children were comparable for growth parameters and neurodevelopment as assessed by the Griffiths scales. There was no evidence of more stress amongst mothers with renal disease or of impaired bonding between mother and child when compared to controls. However, there was evidence of greater externalizing behavioral problems in the group of children born to mothers with renal disease. Engaging families in such studies is challenging. Nonetheless, families who participated appreciated being asked. The children were apparently healthy but there was evidence in this small study of significant antenatal and perinatal morbidity compared to controls. Future larger multi-center studies are required to confirm these early findings
Batalin-Tyutin Quantization of the Self-Dual Massive Theory in Three Dimensions
We quantize the self-dual massive theory by using the Batalin-Tyutin
Hamiltonian method, which systematically embeds second class constraint system
into first class one in the extended phase space by introducing the new fields.
Through this analysis we obtain simultaneously the St\"uckelberg scalar term
related to the explicit gauge-breaking effect and the new type of Wess-Zumino
action related to the Chern-Simons term.Comment: 17 pages, SOGANG-HEP 191/9
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