arXiv subjects

M. Gupta

Publications and source records attributed to M. Gupta.

26 records · Page 2Linked to original sources

arXiv2005

Modified Grover's search algorithm for the cases where the number of solutions is known

Grover's search algorithm searches a database of $N$ unsorted items in $O(\sqrt{N/M})$ steps where $M$ represents the number of solutions to the search problem. This paper proposes a scheme for searching a database of $N$ unsorted items in $O(logN)$ steps, provided the value of $M$ is known. It is also shown that when $M$ is unknown but if we can estimate an upper bound of possible values of $M$, then an improvement in the time complexity of conventional Grover's algorithm is possible. In that case, the present scheme reduces the time complexity to $O(MlogN)$.

quant-ph↗

arXiv2005

Microscopic Description of Super Heavy Nuclei

The results of extensive microscopic Relativistic Mean Field (RMF) calculations for the nuclei appearing in the alpha - decay chains of recently discovered superheavy elements with Z = 109 to 118 are presented and discussed. The calculated ground state properties like total binding energies, Q values, deformations, radii and densities closely agree with the corresponding experimental data, where available. The double folding (t-rho-rho) approximation is used to calculate the interaction potential between the daughter and the alpha, using RMF densities along with the density dependent nucleon - nucleon interaction (M3Y). This in turn, is employed within the WKB approximation to estimate the half lives without any additional parameter for alpha - decay. The half lives are highly sensitive to the Q values used and qualitatively agree with the corresponding experimental values. The use of experimental Q values in the WKB approximation improves the agreement with the experiment, indicating that the resulting interaction potential is reliable and can be used with confidence as the real part of the optical potential in other scattering and reaction processes.

nucl-th↗

arXiv2004

Stability and electronic structure of the complex K$_2$PtCl$_6$ structure-type hydrides

The stability and bonding of the ternary complex K$_2$PtCl$_6$ structure hydrides is discussed using first principles density functional calculations. The cohesion is dominated by ionic contributions, but ligand field effects are important, and are responsible for the 18-electron rule. Similarities to oxides are discussed in terms of the electronic structure. However, phonon calculations for Sr$_2$RuH$_6$ also show differences, particularly in the polarizability of the RuH$_6$ octahedra. Nevertheless, the yet to be made compounds Pb$_2$RuH$_6$ and Be$_2$FeH$_6$ are possible ferroelectrics. The electronic structure and magnetic properties of the decomposition product, FeBe$_2$ are reported. Implications of the results for H storage are discussed.

cond-mat.mtrl-sci↗

arXiv2003

Weighted Density Approximation Description of Insulating YH$_3$ and LaH$_3$

Density functional calculations within the weighted density approximation (WDA) are presented for YH$_3$ and LaH$_3$. We investigate some commonly used pair-distribution functions G. These calculations show that within a consistent density functional framework a substantial insulating gap can be obtained while at the same time retaining structural properties in accord with experimental data. Our WDA band structures agree with those of $GW$ approximation very well, but the calculated band gaps are still 1.0-2.0 eV smaller than experimental findings.

cond-mat↗

arXiv2002

The STAR Photon Multiplicity Detector

Details concerning the design, fabrication and performance of STAR Photon Multiplicity Detector (PMD) are presented. The PMD will cover the forward region, within the pseudorapidity range 2.3--3.5, behind the forward time projection chamber. It will measure the spatial distribution of photons in order to study collective flow, fluctuation and chiral symmetry restoration.

nucl-ex↗

arXiv2001

Magnetism and Electronic Structure in ZnFe$_2$O$_4$ and MnFe$_2$O$_4$

Density functional calculations are used to study magnetic and electronic properties of the spinel ferrites, ZnFe$_2$O$_4$ and MnFe$_2$O$_4$. Correct magnetic orderings are obtained. ZnFe$_2$O$_4$ is predicted to be a small gap insulator in agreement with experiment. MnFe$_2$O$_4$ is found to be a low carrier density half-metal in the fully ordered state. However, strong effects on the electronic structure are found upon partial interchange of Fe and Mn atoms. This indicates that the insulating character may be due to Anderson localization associated with the intersite Mn-Fe disorder.

cond-mat↗

arXiv2000

Implications of the Unitarity Triangle `uc' for J, $δ$ and $|V_{CKM}|$ elements

The Jarlskog rephasing invariant parameter $|J|$ is evaluated using one of the six Unitarity Triangles involving well known CKM matrix elements \vud, \vus,~\rub, ~\vcd, ~\vcs~ and ~\vcb. With PDG2000 values of \vud~ etc. as input, we obtain $|J|=(2.71 \pm 1.12) \times 10^{-5}$, which in the PDG representation of CKM matrix leads to the range $21^o~to~159^o$ for the CP violating phase $δ$. The CKM matrix elements evaluated using this range of $δ$ are in agreement with the PDG CKM matrix. The implications of refinements in the input on $|J|$, $δ$ and CKM matrix elements have also been studied.

hep-ph↗

arXiv1999

Unique Mass Texture for Quarks and Leptons

Texture specific quark mass matrices which are hermitian and hierarchical are examined in detail . In the case of texture 6 zeros matrices, out of sixteen possibilities examined by us, none is able to fit the low energy data (LED), for example, $V_{us} = 0.2196 \pm 0.0023$, $V_{cb} = 0.0395 \pm 0.0017$, $\frac{V_{ub}}{V_{cb}} = 0.08 \pm 0.02$, $V_{td}$ lies in the range $0.004 - 0.013$ (PDG). Similarly none of the 32 texture 5 zeros mass matrices considered is able to reproduce LED. In particular, the latest data from LEP regarding $|V_{ub}|/|V_{cb}|(=0.093\pm0.016)$ rules out all of them. In the texture 4 zeros case, we find that there is a unique texture structure for $U$ and $D$ mass matrices which is able to fit the data.

hep-ph↗