Fundamentals of PV Efficiency Interpreted by a Two-Level Model

Elementary physics of photovoltaic energy conversion in a two-level atomic PV is considered. We explain the conditions for which the Carnot efficiency is reached and how it can be exceeded! The loss mechanisms - thermalization, angle entropy, and below-bandgap transmission - explain the gap between Carnot efficiency and the Shockley-Queisser limit. Wide varieties of techniques developed to reduce these losses (e.g., solar concentrators, solar-thermal, tandem cells, etc.) are reinterpreted by using a two level model. Remarkably, the simple model appears to capture the essence of PV operation and reproduce the key results and important insights that are known to the experts through complex derivations.Comment: 7 pages, 6 figure

The Relevant Operators for the Hubbard Hamiltonian with a magnetic field term

The Hubbard Hamiltonian and its variants/generalizations continue to dominate the theoretical modelling of important problems such as high temperature superconductivity. In this note we identify the set of relevant operators for the Hubbard Hamiltonian with a magnetic field term.Comment: 19 pages, RevTe

AN OVERALL VIEW ON GEMSTONE MINING IN GILGIT-BALTISTAN: PROBLEMS AND MITIGATIONS

Gilgit-Baltistan has tremendous amount of gemstone wealth and thousands of miners are busy to explore this wealth, but due to unscientific and crude mining methods this mineral wealth goes into waste in many ways, like fractures, damages and total destructions of gemstone due to ill blasting methods and lack of proper training. Gemstone mining is done in all districts of Gilgit-Baltistan. According to a careful survey in July 2007, 32 types of Gemstones (Precious and Semiprecious) are found in GB, out of total production of gemstones produced in Pakistan 95% come from GB. According to this survey there are more than 2000 mines which produce different variety of gemstones and numbers of miners involved in this mining industry directly or indirectly are more than 25000.  Due to these crude and unscientific mining methods, improper camps without hygienic facilities, lack of proper mining equipment, lack of basic health facilities and safety tools and lack of mining equipment repairing facilities at mining sites, number of problems are arising. These problems include damage to the fauna and flora in mining areas, damage to the eco system due to blasting and flow of people; mountains are becoming vulnerable due to improper mines development, glaciers melting due to use of thermal generators, spreading of human filth and waste like plastic and at last polluting of the water. This research is based on the mitigation of all these problems to some extent. The damage to the fauna and flora may be reduced by controlling spreading of human filth and waste, controlled blasting may be done by using modern blasting techniques, proper mines of international standard may be developed by enforcing the mining rules, use of thermal generators may be prohibited by developing small hydro projects at sites and at last pollution of water may be controlled by training people to adopt the cleanliness drives time to time and equipment repairing facilities at sites as well.  &nbsp

Renormalization group summation and analytic continuation from spacelike to timeline regions

Analytic continuation of the perturbative series from spacelike to timelike regions is performed using renormalization group summed perturbation theory (RGSPT). This method provides an all-order summation of kinematic ``$\pi^2$-terms'' accessible from a given order of a perturbative series. The impact of the summation of these terms is studied for Higgs boson decay and electromagnetic R-ratio in the perturbative QCD. Results obtained using RGSPT have improved convergence behavior in addition to significantly reduced renormalization scale dependence compared to fixed-order perturbation theory (FOPT). The higher-order behavior using the Pad\'e approximant is also studied for processes considered.Comment: 25 pages and 10 figure

Renormalization Group Improvement and QCD Sum Rules

We summarize the results obtained for the quark masses (u,d,s,c, and b) in Refs.~\cite{AlamKhan:2023ili,AlamKhan:2023kgs} and strong coupling ($\alpha_s$) using renormalization group (RG) improvement of the theoretical expressions and experimental inputs that enter in the QCD sum rules. We obtain $m_{u}(2 GeV)=2.00_{-0.40}^{+0.33}$ MeV, $m_{d}(2 GeV)=4.21_{-0.45}^{+0.48}$ MeV, and $m_{s}(2 GeV)=104.34_{-4.24}^{+4.32}$ MeV using Borel Laplace sum rules for the divergence of the axial vector currents. The relativistic sum rules for the moments of the heavy quark currents lead to the determination of $\alpha_s(M_Z)=0.1171(7)$, $\overline{m}_{c}=1281.1(3.8)$ MeV and $\overline{m}_{b}=4174.3(9.5)$ MeV.Comment: 10 Pages, 10 figures, and updated references. Based on the talk given at the 26th International Conference in HEP (QCD23), 10-14th July 2023, Montpellier-F

Renormalization Group Summation at High Orders and Implications to the Determination of Some Standard Model Parameters

We use renormalization group summed perturbation theory (RGSPT) to improve perturbation series in quantum chromodynamics in the determination of some of the standard model parameters.Comment: PhD Thesi