Quantum Theory Research Articles

Quantum nature of spacetime near the black hole singularity

The concept of spacetime loses its usual interpretation at the essential singularity of a black hole. In consequence, all laws of physics must fail at this classical singularity. This unphysical behavior of spacetime at the singularity originates from general relativity. In order to have a consistent description of spacetime, this singularity must disappear in a quantum mechanical description of spacetime which is expected to be given by a quantum theory of gravity. In this paper, we therefore attempt to describe the quantum nature of spacetime in the vicinity of the (classical) singularity of a black hole. We take the Kantowsi–Sachs representation for the interior spacetime of a black hole and include inevitable vacuum fluctuations of matter field in the Klein–Gordon representation. Hence we obtain the Wheeler–DeWitt equation for the black hole interior and solve this equation exactly yielding a general expression for the interior wave function of the black hole. Admissible wave functions consistent with the DeWitt boundary condition implies that the Hilbert space has three nonoverlapping sectors distinguished by the relative character of the eigenvalues. Regular quantum black holes with admissible and well-behaved wave function having no singularity can exist only in two of those sectors. However, the remaining sector does not contain any regular quantum black hole.

DFT computational and mass spectrometry studies of intermolecular interaction of β-cyclodextrin with nifedipine

A systematic investigation of intermolecular interactions of β- cyclodextrin(β-CD)and Nifedipine(Nif)in gas phase and in water were done by the mass spectrometry and DFT calculation method. The results obtained clearly indicated that the aromatic ring containing the nitro moiety of Nifedipine inverted into the wider rim of β cyclodextrin, the high collision induced dissociation (CID) energy in mass spectrometry experiments demonstrated the stability of the 1:1 Nif-β-CD complexes. Compared to the native β-CD, HP- β-CD and DM- β-CD are more easily to form complexes with Nif due to their approximately double lower binding energy, the thermodynamic parameters, HOMO, LUMO, the global reactivity descriptors of these complexes were calculated and interpreted. Furthermore, the study of natural bonding orbitals (NBO) and quantum theory of protons in molecules (QTAIM) supports the existence of various hydrogen bonds and van der Waals interactions in three complex structures, as predicted by chemical bonding principles. IGMH analysis give the visualized origin of weak attractive interactions between the CDs and the Nifedipine.

Adsorption of aminomethylphosphonic acid on pristine graphene and graphene doped with transition metals: A theoretical study

Aminomethylphosphonic acid (AMPA), a glyphosate breakdown product, exhibits environmental persistence, raising concerns. This study investigates AMPA adsorption on pristine and transition metal-doped graphene using quantum theory of atoms in molecules calculations. Results revealed favorable adsorption energies for pristine graphene, significantly enhanced by doping, with Co-doped graphene exhibiting the highest adsorption energy. Interactions were predominantly physisorption, and doping did not significantly alter graphene’s electronic structure. Tight-binding dynamics simulations demonstrated efficient AMPA adsorption on doped graphene, with Co exhibiting the strongest binding affinity. These findings highlight the potential of transition metal-doped graphene as an effective adsorbent for removing AMPA from water sources.

An advance in the arithmetic of the Lie groups as an alternative to the forms of the Campbell-Baker-Hausdorff-Dynkin theorem

The exponential of an operator or matrix is widely used in quantum theory, but it sometimes can be a challenge to evaluate. For non-commutative operators X and Y, according to the Campbell-Baker-Hausdorff-Dynkin theorem, e X+Y is not equivalent to e X e Y , but is instead given by the well-known infinite series formula. For a Lie algebra of a basis of three operators {X, Y, Z}, such that [X, Y] = κ Z for scalar κ and cyclic permutations, here it is proven that e a X+b Y is equivalent to e p Z e q X e−p Z for scalar p and q. Extensions for e a X+b Y+c Z are also provided. This method is useful for the dynamics of atomic and molecular nuclear and electronic spins in constant and oscillatory transverse magnetic and electric fields.

Size-Dependent Fullerenes for Enhanced Interaction of l-Leucine: A Combined DFT and MD Simulations Approach.

Fullerene-based biosensors have received great attention due to their unique electronic properties that allow them to transduce electrical signals by accepting electrons from amino acids. Babies with MSUD (maple syrup urine disease) are unable to break down amino acids such as l-leucine, and excess levels of the l-leucine are harmful. Therefore, sensing of l-leucine is foremost required. We aim to investigate the interaction tendencies of size-variable fullerenes (CX; X = 24, 36, 50, and 70) toward l-leucine (LEU) using density functional theory (DFT-D3) and classical molecular dynamics (MD) simulation. The C24 fullerene shows the highest affinity of the LEU biomolecule in the gas phase. Smaller fullerenes (C24 and C36) show stronger interactions with leucine due to their higher curvature in water environments. Moreover, recovery times in the ranges of 1010 and 104 s make it a viable candidate for the isolation application of LEU from the biological system. Further, the interaction between LEU and fullerenes is in line with the natural bond order (NBO) analysis, Mulliken charge analysis, quantum theory atom in molecule (QTAIM) analysis, and reduced density gradient (RDG) analysis. At 310 K, employing the explicit water model in classical MD simulations, fullerenes C24 and C36 demonstrate notably elevated binding free energies (-24.946 kJ/mol) in relation to LEU, showcasing their potential as sensors for l-leucine. Here, we demonstrate that the smaller fullerene exhibits a higher potential for l-leucine sensors than the larger fullerene.

Collective quantum phenomena and their applications

Collective quantum phenomena and their applications John H. Miller, Jr., University of Houston (UH), from the Dept. of Physics and Texas Center for Superconductivity, explains collective quantum phenomena and their applications. The evidence supporting the quantum behavior of electrons, as well as every other known particle in the universe, is overwhelming. On the centennial anniversary of Max Planck’s seminal paper on energy quantization (1), Kleppner and Jackiw pointed out, “Quantum theory is the most precisely tested and most successful theory in the history of science”. (2)

Geometric Hawking radiation of Schwarzschild Black Hole with novel quantum algebra

In the context of an extended General Relativity theory with boundary terms included, we introduce a new nonlinear quantum algebra involving a quantum differential operator, with the aim to calculate quantum geometric alterations when a particle is created in the vicinity of a Schwarzschild black-hole by the Hawking radiation mechanism. The boundary terms in the varied action give rise to modifications in the geometric background, which are investigated by analyzing the metric tensor and the Ricci curvature within the framework of a renormalized quantum theory of gravity.

Energetic features of H-bonded and antiparallel π-stacked supramolecular assemblies in pyrazolones: Experimental, computational and biological analyses

The work presented herein outlines a straightforward synthetic route to produce a series of pyrazolone compounds, which are significant in both coordination chemistry and pharmaceutical research. These heterocyclic compounds were thoroughly characterized using FTIR, 1H and 13C NMR spectroscopy, and their molecular structures were conclusively determined through X-ray crystallography. The resulting supramolecular architectures feature a variety of noncovalent interactions, including conventional NH…O and CH…O hydrogen bonds, CH…halogen contacts, CH…N interactions, and offset π-π stacking. Density Functional Theory (DFT) calculations, alongside Molecular Electrostatic Potential (MEP) surface analysis and Quantum Theory of Atoms in Molecules (QTAIM)/Non-Covalent Interaction (NCI) plot methodologies, were employed to probe these interactions further. This analysis highlighted the significance of both CH…O and NH…O hydrogen bonds and revealed the critical role of antiparallel π-stacking interactions, particularly within chlorophenyl and benzonitrile substituted pyrazolones, underscoring their stabilizing effects on the molecular structure. Biological assessment against urease enzyme unveiled compound 3a as the lead inhibitor with an IC50 value of 0.71 ± 0.09 μM and 31-folds strong inhibition than thiourea, thus making pyrazolone heterocycles as potential drug candidates.

Nature of the bond in intermetallic compounds

By studying 398 binary compounds crystallizing in five different crystal structures, it is shown that atomic radii of the elements RA and RB change to reach a constant radius ratio rA/rB(≡ϒ) in a cubic system. In systems of lower symmetry, a range of ϒ values, each corresponding to a certain axial ratio, is possible. Accurate charge values on atoms in solids are derived from the experimental internal radii rA and rB, using Shannon’s compilation of radii versus charge states for elements. It is found, for the first time, that charge transfer and radii change reverse their direction at the ϒ point. Electronegativity difference relative to its value at the ϒ point is recognized to correctly predict the charge transfer and radii changes with RA/RB. The deduced electronic structure of solids, based on spherical ions carrying partial charges, confirms that the metallic atom-pair bond is a resonating polar covalent bond. Identification of the number of electrons that contribute to cohesion and electrical conduction individually, allows successful prediction of electrical conductivity variation for transition metals and p-elements in the periodic table. From a knowledge of accurate valence of elements and of charge on the atoms, variation in the 197Au isomer shift of the gold compounds of CsCl type structure is predicted. The charges on atoms computed using the Quantum Theory of Atoms in Molecules (QTAIM) technique agree with those obtained in our work for compounds belonging to two of the structure types. For compounds belonging to the other three, the charge values obtained by the two methods do not agree. The disagreement correlates to not reckoning the role of the ϒ point. The effect of ϒ point is so fundamental and universal that most physical properties obtained by the secondary processing of primary DFT data, can be influenced by it.

Sensitive determination of Gabapentin in plasma sample using dispersive liquid-liquid microextraction coupled with ion mobility spectrometry

Gabapentin (GBP) is an anticonvulsant agent and its determination using a fast and simple method is challenging. In this research, a novel sensitive, and economical method for the fast determination of GBP in biological samples was developed. This method benefits from the advantages of ion mobility spectrometry (IMS) as a fast detection and separation system and dispersive liquid-liquid microextraction (DLLME) for the preconcentration/extraction of GBP. In the developed method (DLLME-IMS), Ag nanoparticles serve as modifiers. Moreover, the quantum theory of atoms in molecules (QTAIM) analysis was employed to investigate the interaction mechanism between GBP and Ag nanoparticles. Also, a delay time after the injection of the sample was applied to improve the method sensitivity. Under the optimum condition, the developed method showed a linear response over the concentration range of 0.3–12 μg mL−1 and a detection limit of 0.12 μg mL−1. Eventually, DLLME-IMS was successfully employed in plasma sample, and was validated against the HPLC method with UV detection as a reference method. The developed method will open up a new avenue for the development of effective, rapid, and simple analytical methods.

Scientific Objectivity and Its Limits

Measurement outcomes provide data for a physical theory. Unless they are objective they support no objective scientific knowledge. So the outcome of a quantum measurement must be an objective physical fact. But recent arguments purport to show that if quantum theory is universally applicable then there is no such fact. This calls for a reappraisal of the notions of fact and objectivity. If quantum theory is universally applicable the facts about the physical world include a fact about each quantum measurement outcome. These physical facts lack an ideal kind of objectivity but their more modest objectivity is all that science needs.

Investigating the potential of monocyclic B9N9 and C18 rings for the electrochemical sensing, and adsorption of carbazole-based anti-cancer drug derivatives: DFT-based first-principle study.

For the first time, the use of monocyclic rings C18 and B9N9 as sensors for the sensing of carbazole-based anti-cancer drugs, such as tetrahydrocarbazole (THC), mukonal (MKN), murrayanine (MRY), and ellipticine (EPT), is described using DFT simulations and computational characterization. The geometries, electronic properties, stability studies, sensitivity, and adsorption capabilities of C18 and B9N9 counterparts towards the selected compounds confirm that the analytes interact through active cavities of the C18 and B9N9 rings of the complexes. Based on the interaction energies, the sensitivity of surfaces towards EPT, MKN, MRY, and THC analytes is observed. The interaction energy of EPT@B9N9, MKN@B9N9, MRY@B9N9, and THC@B9N9 complexes are observed - 20.40, - 19.49, - 20.07, and - 18.27kcal/mol respectively which is more exothermic than EPT@C18, MKN@C18, MRY@C18, and THC@C18 complexes are - 16.37, - 13.97, - 13.96, and - 11.39kcal/mol respectively. According to findings from the quantum theory of atoms in molecules (QTAIM) and the reduced density gradient (RDG), dispersion forces play a significant role in maintaining the stability of these complexes. The electronic properties including FMOs, density of states (DOS), natural bond orbitals (NBO), charge transfer, and absorption studies are carried out. In comparison of B9N9 and C18, the analyte recovery time for C18 is much shorter (9.91 × 10-11 for THC@C18) than that for B9N9 shorter recovery time value of 3.75 × 10-9 for EPT@B9N9. These results suggest that our reported sensors B9N9 and C18 make it faster to detect adsorbed molecules at room temperature. The sensor response is more prominent in B9N9 due to its fine energy gap and high adsorption energy. Consequently, it is possible to think of these monocyclic systems as a potential material for sensor applications.

Sir Roger James Elliott. 8 December 1928—16 April 2018

Roger James Elliott was a theoretical physicist and pioneer in the use of quantum theory in solid state physics, which happened a few years after the invention of quantum mechanics in the late 1920s and which spread into all areas of solid state physics during the years when Roger Elliott was active (roughly the second half of the twentieth century, 1950–2000). He specialized in the magnetic, semiconductor and optical properties of condensed matter, with a particular emphasis on the effects caused by disorder—that is, the absence of periodicity in alloys and amorphous materials. He studied at New College, Oxford, before working as a postdoc at Berkeley. He then returned to England, first to Harwell and then to a faculty position at the University of Reading. During this time he completed his seminal work on the general theory of the optical properties of excitons. He returned to Oxford in 1957, where he was to stay for the remaining 60 years, until his death in 2018. He was the Wykeham professor of physics from 1974 until 1988, and he was awarded the Maxwell Medal in 1968 and the Guthrie Medal in 1990, both from the Institute of Physics. He was knighted in 1987. In his later years he was very active in the Royal Society as Foreign Secretary and also in scientific publishing worldwide after he served as chief executive of Oxford University Press from 1988 until 1993.

Extremal Tsirelson Inequalities.

It is well known that the set of statistics that can be observed in a Bell-type experiment is limited by quantum theory. Unfortunately, tools are missing to identify the precise boundary of this set. Here, we propose to study the set of quantum statistics from a dual perspective. By considering all Bell expressions saturated by a given realization, we show that the Clauser-Horne-Shimony-Holt expression can be decomposed in terms of extremal Tsirelson inequalities that we identify. This brings novel insight into the geometry of the quantum set in the (2,2,2) scenario. Furthermore, this allows us to identify all the Bell expressions that are able to self-test the Tsirelson realization.

Rotational Spectroscopy of the Acetone-Water Complex: Large Amplitude Motions.

Acetone (CH3COCH3), the simplest ketone, has recently attracted considerable attention for its important role in atmospheric chemistry and in the formation of ices in extraterrestrial sources that contain complex organic molecules. In this study, we employed a combination of experimental rotational spectroscopy and quantum chemistry calculations to investigate the structure and dynamics of the acetone-water complex. Our aim was to understand how non-covalent interactions with water affect the methyl internal rotation dynamics of acetone, and how water-centered large amplitude motions alter the observed physical properties compared to those predicted at the equilibrium position. Detailed rotation-tunneling analyses of acetone-H2O and -D2O reveal that the interactions with water disrupt the equivalence of the two methyl rotors, resulting in a noticeably lower methyl rotor barrier for the top with the close-by water compared to that of free acetone. The barrier for the methyl group further from water is also lower, although to a lesser degree. To gain further insights, extensive theoretical modelling was conducted, focusing on the associated large amplitude motions. Furthermore, quantum theory of atoms in molecules and non-covalent interactions analyses were utilized to visualize the underlying causes of the observed trends.

Structural and theoretical exploration of a multi-methoxy chalcone: Synthesis, quantum theory, electrostatics, molecular packing, DFT analysis, and in-silico anti-cancer evaluation

This study explores the pharmacological potential of chalcones through a multidisciplinary approach, including synthesis, quantum theory, molecular electrostatics, and density functional theory (DFT) calculations. The synthesized compound, analyzed via single crystal X-ray diffraction, crystallized in the triclinic system (space group P-1) with C–H⋯O interactions stabilizing its structure. Hirshfeld surface analysis confirms these interactions, with H–H contacts dominating (45.1 %). Molecular electrostatics analysis reveals charge distribution, and a 3.10 eV HOMO-LUMO energy gap indicates bioactivity. Molecular docking identifies the compound (3a) showed a maximum Gscore of HTNF-α (−9.81 kcal/mol); Tubulin (−7.96 kcal/mol); COX2 (−7.88 kcal/mol), EGFR (−6.72 kcal/mol), and VEGFR1(-2.50 kcal/mol). Where compound (3c) showed maximum binding at the putative binding site with dock scores for VEGFR2 (−9.24 kcal/mol). This research not only advances molecular science but also holds promise for diverse applications, including drug design. The significance of this study lies in its comprehensive exploration of the pharmacological potential of chalcones using a multidisciplinary approach. Through the integration of synthesis, quantum theory, molecular electrostatics, and density functional theory (DFT) calculations, we have extensively explored the structural and biochemical characteristics of these compounds. This investigation has revealed valuable insights that have the potential to lead to significant advancements in the fields of molecular science and drug design. Moreover, the molecular docking studies shed light on the compound's interaction with various biological targets. The significant binding affinities observed for these targets underscore the potential therapeutic relevance of the synthesized compound in diverse disease conditions.

Structural Investigation of Schiff Base Ligand and Dinuclear Copper Complex: Synthesis, Crystal Structure, Computational, and Latent Fingerprint Analysis.

The structural studies of the fluorinated Schiff base ligand and its copper complex were synthesized and characterized by Fourier transform infrared, UV-visible, and photoluminescence spectroscopy. Single-crystal X-ray diffraction analysis unveils a dinuclear copper complex arising from double bridging acetate anions to copper ions that are chelated by the tridentate Schiff base ligand Cu(LS). The trigonality index τ5 of 0.080 indicates a distorted square pyramidal coordination geometry for the metal. The SL ligand and complex exhibit intra- and intermolecular interactions, leading to unique supramolecular architectures. The structural changes between the free halogenated Schiff base ligand and upon coordination with the metal were extensively studied by experimental and theoretical approaches. The intra- and intermolecular interactions have been analyzed by Hirshfeld surface and quantum theory of atoms in molecules analysis, and the enrichment ratio highlights the most favored interactions in the formation of molecular packing. The chemical and physical properties, such as the HOMO - LUMO energy gap, chemical reactivity, and electron density topology, are studied using density functional theory studies. In addition, the Schiff base ligand compound is used to study the latent fingerprint analysis.

Feedback cooling a levitated nanoparticle's libration to below 100 phonons

Macroscopic rotors are interesting model systems to test quantum theory and for quantum sensing. A promising approach for bringing these systems to the quantum regime is to combine sensitive detection with feedback cooling to reduce the thermal occupation of the mechanics. Here, we implement a backward-scattering scheme to efficiently detect all three libration modes of an optically levitated nanoparticle. We demonstrate parametric feedback cooling of all three libration degrees of freedom to below 16 mK, with one of the modes reaching the temperature of 1.3 mK, corresponding to a mean phonon number of 84. Finally, we characterize the backward-scattering scheme by determining its measurement efficiency to be 0.5%. Published by the American Physical Society 2024

Quantum theory of phonon-induced anomalous Hall effect in two-dimensional massive Dirac metals

Quantum theory of phonon-induced anomalous Hall effect in two-dimensional massive Dirac metals

Optimization and mechanistic insight of phenol removal using an effective green kaolin adsorbent through experimental and computational approaches

The discharge of phenols into the aquatic environment has detrimentally affected human health and the aquatic ecosystem. Hence, removing phenols from polluted water bodies has been a global concern. In this study, a natural and low-cost adsorbent, kaolin, was used to remove phenol from aqueous solutions. Experimental and computational approaches were applied to optimize the removal efficiency and provide mechanistic insight into the phenol removal process. Based on the response surface methodology findings, the optimum conditions were pH 1.6, 40 min, 50 mg/L, and 2 g with 92.19 % maximum percentage removal. The regeneration test shows that kaolin retained over 76.76 % of adsorption capacities. SEM and FESEM reveals the surface morphology and effectiveness of kaolin as phenol removal. The best fit for the Isotherm adsorption for the phenol on kaolin is Freundlich isotherm, which indicated multilayer adsorption. The hydroxyl group from phenol (-OH) and the siloxane group of kaolin (Si-O-Si) shifted, suggesting the presence of a hydrogen bond between kaolin and phenol during adsorption, as determined by one- and two-dimensional IR spectroscopy. Density functional theory calculations were used to support the experimental results by providing information on the Mulliken charge and electronic transition of the complex to improve understanding of the adsorption of phenol on kaolin. Based on the quantum theory of atoms in molecules analysis (QTAIM) and the reduced density gradient non-covalent interaction (RDG-NCI) technique, the chemical reaction occurring during the removal of phenol by kaolin was determined to occur through hydrogen bonding and classified as an intermediate type (∇2ρ(r) > 0 and H < 0). Further characterizations employing molecular electrostatic potential, global reactivity, and local reactivity descriptors were conducted to investigate the mechanism of the phenol adsorption on kaolin. The findings demonstrated that phenol functions as an electrophile while kaolin acts as a nucleophile during the formation of hydrogen bonds, where the interaction occurred between the O2 atom of kaolin (electron donor) and the H13 atom of phenol (electron acceptor).