316 research outputs found
Constraint structure in modified Faddeev-Jackiw method
We show that in modified Faddeev-Jackiw formalism, first and second class
constraints appear at each level, and the whole constraint structure is in
exact correspondence with level by level method of Dirac formalism.Comment: 11 pages, No figure
Boundary Conditions as Dirac Constraints
In this article we show that boundary conditions can be treated as Lagrangian
and Hamiltonian constraints. Using the Dirac method, we find that boundary
conditions are equivalent to an infinite chain of second class constraints
which is a new feature in the context of constrained systems. Constructing the
Dirac brackets and the reduced phase space structure for different boundary
conditions, we show why mode expanding and then quantizing a field theory with
boundary conditions is the proper way. We also show that in a quantized field
theory subjected to the mixed boundary conditions, the field components are
noncommutative.Comment: 18 pp, Latex, minor changes, typos correcte
Perfect and Imperfect Gauge Fixing
Gauge fixing may be done in different ways. We show that using the chain
structure to describe a constrained system, enables us to use either a perfect
gauge, in which all gauged degrees of freedom are determined; or an imperfect
gauge, in which some first class constraints remain as subsidiary conditions to
be imposed on the solutions of the equations of motion. We also show that the
number of constants of motion depends on the level in a constraint chain in
which the gauge fixing condition is imposed. The relativistic point particle,
electromagnetism and the Polyakov string are discussed as examples and perfect
or imperfect gauges are distinguished.Comment: 19 pages, no figur
The BFT Method With Chain Structure
We have constructed a modified BFT method that preserves the chain structure
of constraints. This method has two advantages: first, it leads to less number
of primary constraints such that the remaining constraints emerge
automatically; and second, it gives less number of independent gauge
parameters. We have applied the method for bosonized chiral Schwiger model. We
have constructed a gauge invariant embedded Lagrangian for this model.Comment: To appear in Phys. Lett.
On 3D Minimal Massive Gravity
We study linearized equations of motion of the newly proposed three
dimensional gravity, known as minimal massive gravity, using its metric
formulation. We observe that the resultant linearized equations are exactly the
same as that of TMG by making use of a redefinition of the parameters of the
model. In particular the model admits logarithmic modes at the critical points.
We also study several vacuum solutions of the model, specially at a certain
limit where the contribution of Chern-Simons term vanishes.Comment: 15 pages, no figures, typos fixed, journal versio
Natural Cytotoxicity of NC-2(+) Cells Against the Growth and Metastasis of WEHI-164 Fibrosarcoma
We have previously reported a new receptor (NC-2) for natural cytotoxicity (NC) on murine leucocytes, identified by monoclonal antibody D9 (mAb D9). Pretreatment of mouse spleen cells with different concentrations of mAb D9 in vitro blocked NC against WEHI-164, whereas natural killing (NK) activity against YAC-1 was unaffected. This paper reports the immune surveillance against the growth of WEHI-164 tumour cells in mice by NC-2+ Cells. The kinetics of in vivo reduction in NC activity were investigated by treating BALB/c and (CBA x C57BL/6) F1 mice with a single injection of 40 mu g of mAb D9 and monitoring splenic NC activity by 51Cr-release assay at intervals from 24 h to 3 weeks. Control mice were injected with OKT8 irrelevant antibody. Results showed a significant (P < 0.05) reduction in splenic NC activity within 24 h which persisted for up to 1 week. Similar results were also obtained when (CBA x C57BL/6) F1 mice were employed (P < 0.001). In vivo tumour studies were undertaken to investigate the role of NC-2+ cells in surveillance against tumour growth and metastasis of the WEHI-164 fibrosarcoma. When syngeneic BALB/c mice were injected with 40 mu g of mAb D9 and then challenged with 5 x 105 WEHI-164 cells, results showed significantly increased growth rate of the transplanted WEHI-164 fibrosarcoma and tumour nodules in the lungs of animals, when compared to control mice with normal NC activity. Our data support an innate surveillance in metastasis and growth of WEHI-164 fibrosarcoma in mice
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