Preparation of graphene oxide from coal

Nanomaterial synthesis from low-cost precursors is a highly desirable approach for bulk application in material science and technology. Among the various nanomaterials, graphene is a single layer two-dimensional honeycomb carbon nanomaterial. Graphene /or graphene oxide is widely utilized in material science, bio-medicine technology as a sensor, cellular imaging, and many more due to its surface area, nanoscale size, and electrical charge properties, etc. Coal is the most abundant combustible energy source. Although, coal possesses a very complex structure, however, it consists significant amount of polyaromatic structure. Due to the presence of an inherent polyaromatic structure, coal becomes a promising candidate to replace graphite as a precursor material for the production of graphene / or graphene oxide. Herein, a facile cost-effective approach is reported to synthesize graphene oxide from low-grade coal

A Numerical Experiment in DLCQ: Microcausality, Continuum Limit and all that

Issues related with microcausality violation and continuum limit in the context of (1+1) dimensional scalar field theory in discretized light-cone quantization (DLCQ) are addressed in parallel with discretized equal time quantization (DETQ) and the fact that Lorentz invariance and microcausality are restored if one can take the continuum limit properly is emphasized. In the free case, it is shown with numerical evidence that the continuum results can be reproduced from DLCQ results for the Pauli-Jordan function and the real part of Feynman propagator. The contributions coming from $k^+$ near zero region in these cases are found to be very small in contrast to the common belief that $k^+=0$ is an accumulation point. In the interacting case, aspects related to the continuum limit of DLCQ results in perturbation theory are discussed.Comment: Minor changes in the text, accepted for publication in Phys. Letts.

Sum rule for the twist four longitudinal structure function

We investigate the twist four longitudinal structure function $F_{L}^{\tau=4}$ of deep inelastic scattering and show that the integral of ${F_{L}^{\tau=4} \over x}$ is related to the expectation value of the fermionic part of the light-front Hamiltonian density at fixed momentum transfer. We show that the new relation, in addition to providing physical intuition on $F_{L}^{\tau=4}$, relates the quadratic divergences of $F_{L}^{\tau=4}$ to the quark mass correction in light-front QCD and hence provides a new pathway for the renormalization of the corresponding twist four operator. The mixing of quark and gluon operators in QCD naturally leads to a twist four longitudinal gluon structure function and to a new sum rule $\int dx {F_L \over x}= 4 {M^2 \over Q^2}$, which is the first sum rule obtained for a twist four observable. The validity of the sum rule in a non-perturbative context is explicitly verified in two-dimensional QCD.Comment: To appear in Physics Letters

Transverse Spin in QCD and Transverse Polarized Deep Inelastic Scattering

We address the long standing problem of the construction of relativistic spin operators for a composite system in QCD. Exploiting the kinematical boost symmetry in light front theory, we show that transverse spin operators for massless particles can be introduced in an arbitrary reference frame, in analogy with those for massive particles. In light front QCD, the complete set of transverse spin operators are identified for the first time, which are responsible for the helicity flip of the nucleon. We establish the direct connection between transverse spin in light front QCD and transverse polarized deep inelastic scattering. We discuss the theoretical and phenomenological implications of our results.Comment: Title and presentation slightly changed, results unchanged, accepted for publication in Phys. Lett.

Utility of Galilean Symmetry in Light-Front Perturbation Theory: A Nontrivial Example in QCD

Investigations have revealed a very complex structure for the coefficient functions accompanying the divergences for individual time ($x^+$) ordered diagrams in light-front perturbation theory. No guidelines seem to be available to look for possible mistakes in the structure of these coefficient functions emerging at the end of a long and tedious calculation, in contrast to covariant field theory. Since, in light-front field theory, transverse boost generator is a kinematical operator which acts just as the two-dimensional Galilean boost generator in non-relativistic dynamics, it may provide some constraint on the resulting structures. In this work we investigate the utility of Galilean symmetry beyond tree level in the context of coupling constant renormalization in light-front QCD using the two-component formalism. We show that for each $x^+$ ordered diagram separately, underlying transverse boost symmetry fixes relative signs of terms in the coefficient functions accompanying the diverging logarithms. We also summarize the results leading to coupling constant renormalization for the most general kinematics.Comment: RevTeX, five PostScript figure