scholarly journals Least-order torsion-gravity for fermion fields, and the nonlinear potentials in the standard models

2014 ◽  
Vol 11 (08) ◽  
pp. 1450073 ◽  
Author(s):  
Luca Fabbri
Keyword(s):  
Zero Point ◽  
Matter Field ◽  
Single Model ◽  
Point Energy ◽  
Fermion Fields ◽  
Nonlinear Potentials ◽  
Standard Models ◽  
The One ◽  
In The Beginning ◽  
Matter Fields

We will consider the least-order torsional completion of gravity for a spacetime filled with fermionic Dirac matter fields, and we study the effects of the background-induced nonlinear potentials for the matter field themselves, in terms of their effects for both standard models of physics: from the one of cosmology to that of particles, we will discuss the mechanisms of generation of the cosmological constant and particles masses as well as the phenomenology of leptonic weak-like forces and neutrino oscillations, the problem of zero-point energy, how there can be neutral massive fields as candidates for dark matter, and the avoidance of gravitationally-induced singularity formation; we will show the way in which all these different effects can nevertheless be altogether described in terms of just a single model, which will be discussed in the beginning.

STRUCTURAL, ELECTRONIC, AND OPTICAL PROPERTIES OF ZnxSy (x + y = 2 TO 4) NANOCLUSTERS: A B3LYP-DFT STUDY

2011 ◽  
Vol 10 (01n02) ◽  
pp. 341-344
Author(s):  
P. S. YADAV ◽  
D. K. PANDEY ◽  
S. AGRAWAL ◽  
B. K. AGRAWAL
Keyword(s):  
Optical Properties ◽  
Visible Region ◽  
Zero Point ◽  
Binding Energies ◽  
Ultraviolet Region ◽  
Point Energy ◽  
Electronic And Optical Properties ◽  
The Stability ◽  
The One ◽  
Homo Lumo

The stability, structural, electronic, and optical properties have been studied for most stable zinc sulfide nanoclusters Zn x S y (x + y = n = 2 to 4). A B3LYP-DFT/6-311G(3df) method is employed to optimize the geometries, and a TDDFT method is used for the study of the optical properties. The binding energies (BE), HOMO–LUMO gaps and the bond lengths have been obtained for all the clusters. We have considered also the zero point energy (ZPE) corrections ignored by the earlier workers. For a fixed value of n, we designate the most stable structure the one, which has maximum final binding energy per atom. The adiabatic and vertical ionization potentials (IP) and electron affinities (EA), charge on atoms, dipole moment, and optical properties have been investigated for the most stable structures. The nanoclusters containing large number of S atoms for each "n" are found to be most stable. Except for ZnS nanocluster, the HOMO–LUMO gap increases with the number of S atoms. Similarly, except for ZnS , IP and EA fluctuate with the cluster size but reveal downward trend. The optical absorption is quite weak in visible region but is strong in the ultraviolet region in most of the nanoclusters except a few. The growth of most stable nanoclusters may be possible in the experiments.

scholarly journals INTRINSICALLY QUANTUM-MECHANICAL GRAVITY AND THE COSMOLOGICAL CONSTANT PROBLEM

2011 ◽  
Vol 26 (32) ◽  
pp. 2375-2389 ◽  
Author(s):  
PHILIP D. MANNHEIM
Keyword(s):  
Cosmological Constant ◽  
Conformal Symmetry ◽  
Zero Point ◽  
Dynamical Symmetry ◽  
Matter Field ◽  
Quantum Mechanical ◽  
Conformal Invariant ◽  
Cosmological Constant Problem ◽  
The Universe ◽  
Matter Fields

We propose that gravity be intrinsically quantum-mechanical, so that in the absence of quantum mechanics the geometry of the universe would be Minkowski. We show that in such a situation gravity does not require any independent quantization of its own, with it being quantized simply by virtue of its being coupled to the quantized matter fields that serve as its source. We show that when the gravitational and matter fields possess an underlying conformal symmetry, the gravitational field and fermionic matter-field zero-point fluctuations cancel each other identically. Then, when the fermions acquire mass by a dynamical symmetry breaking procedure that induces a cosmological constant in such conformal theories, the zero-point fluctuations readjust so as to cancel the induced cosmological constant identically. The zero-point vacuum problem and the cosmological constant vacuum problems thus mutually solve each other. We illustrate our ideas in a completely solvable conformal-invariant model, namely two-dimensional quantum Einstein gravity coupled to a Nambu–Jona-Lasinio self-consistent fermion.

Principle of equivalence at Planck scales and the zero-point length of spacetime — A synergistic description of quantum matter and geometry

2020 ◽  
Vol 29 (14) ◽  
pp. 2042005
Author(s):  
T. Padmanabhan
Keyword(s):  
Zero Point ◽  
Matter Field ◽  
The Self ◽  
Quantum Geometry ◽  
Principle Of Equivalence ◽  
Quantum Matter ◽  
Specific Manner ◽  
Self Gravity ◽  
Matter Fields ◽  
Quantum Spacetime

At mesoscopic scales close to, but somewhat larger than, Planck length, one could describe quantum spacetime and matter in terms of a quantum-corrected geometry. The key feature of such a description is the introduction of a zero-point length into the spacetime. When we proceed from quantum geometry to quantum matter, the zero-point length will introduce corrections in the propagator of matter field in a specific manner. On the other hand, one cannot ignore the self-gravity of matter fields at the mesoscopic scales and this will also modify the form of the propagator. Consistency demands that these two modifications coming from two different directions are the same. I show that this nontrivial demand is actually satisfied. Surprisingly, the principle of equivalence, operating at Planck scales, ensures this consistency in a subtle manner.

scholarly journals Matter Localization on Brane-Worlds Generated by Deformed Defects

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Alex E. Bernardini ◽  
Roldão da Rocha
Keyword(s):  
Matter Field ◽  
Brane Worlds ◽  
Fermion Fields ◽  
Internal Structures ◽  
Global Action ◽  
Boson Fields ◽  
Mass Terms ◽  
Matter Fields ◽  
Thick Branes ◽  
Kaluza Klein

Localization and mass spectrum of bosonic and fermionic matter fields of some novel families of asymmetric thick brane configurations generated by deformed defects are investigated. The localization profiles of spin 0, spin 1/2, and spin 1 bulk fields are identified for novel matter field potentials supported by thick branes with internal structures. The condition for localization is constrained by the brane thickness of each model such that thickest branes strongly induce matter localization. The bulk mass terms for both fermion and boson fields are included in the global action as to produce some imprints on mass-independent potentials of the Kaluza-Klein modes associated with the corresponding Schrödinger equations. In particular, for spin 1/2 fermions, a complete analytical profile of localization is obtained for the four classes of superpotentials here discussed. Regarding the localization of fermion fields, our overall conclusion indicates that thick branes produce aleft-right asymmetric chirallocalization of spin 1/2 particles.

On the Use of Quantum Thermal Bath in Unimolecular Fragmentation Simulations

2019 ◽  
Author(s):  
Riccardo Spezia ◽  
Hichem Dammak
Keyword(s):  
Degrees Of Freedom ◽  
Molecular Simulations ◽  
Zero Point ◽  
Thermal Bath ◽  
Unimolecular Dissociation ◽  
Point Energy ◽  
Rotational Degrees Of Freedom ◽  
The Difference ◽  
Nuclear Effects

<div> <div> <div> <p>In the present work we have investigated the possibility of using the Quantum Thermal Bath (QTB) method in molecular simulations of unimolecular dissociation processes. Notably, QTB is aimed in introducing quantum nuclear effects with a com- putational time which is basically the same as in newtonian simulations. At this end we have considered the model fragmentation of CH4 for which an analytical function is present in the literature. Moreover, based on the same model a microcanonical algorithm which monitor zero-point energy of products, and eventually modifies tra- jectories, was recently proposed. We have thus compared classical and quantum rate constant with these different models. QTB seems to correctly reproduce some quantum features, in particular the difference between classical and quantum activation energies, making it a promising method to study unimolecular fragmentation of much complex systems with molecular simulations. The role of QTB thermostat on rotational degrees of freedom is also analyzed and discussed. </p> </div> </div> </div>

scholarly journals Hierarchical structure of physical Yukawa couplings from matter field Kähler metric

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Keiya Ishiguro ◽  
Tatsuo Kobayashi ◽  
Hajime Otsuka
Keyword(s):  
String Theory ◽  
Hierarchical Structure ◽  
Matter Field ◽  
Heterotic String ◽  
Heterotic String Theory ◽  
Kähler Metric ◽  
Yukawa Couplings ◽  
String Compactifications ◽  
Kahler Metric ◽  
Matter Fields

Abstract We study the impacts of matter field Kähler metric on physical Yukawa couplings in string compactifications. Since the Kähler metric is non-trivial in general, the kinetic mixing of matter fields opens a new avenue for realizing a hierarchical structure of physical Yukawa couplings, even when holomorphic Yukawa couplings have the trivial structure. The hierarchical Yukawa couplings are demonstrated by couplings of pure untwisted modes on toroidal orbifolds and their resolutions in the context of heterotic string theory with standard embedding. Also, we study the hierarchical couplings among untwisted and twisted modes on resolved orbifolds.

scholarly journals Modulation of optical absorption in m-Fe1−xRuxS2 and exploring stability in new m-RuS2

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
H. Joshi ◽  
M. Ram ◽  
N. Limbu ◽  
D. P. Rai ◽  
B. Thapa ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Phonon Dispersion ◽  
Applied Pressure ◽  
Orthorhombic Phase ◽  
Zero Point ◽  
Computational Method ◽  
Crystal Field Theory ◽  
Point Energy ◽  
Practical Applications ◽  
New Phase

AbstractA first-principle computational method has been used to investigate the effects of Ru dopants on the electronic and optical absorption properties of marcasite FeS2. In addition, we have also revealed a new marcasite phase in RuS2, unlike most studied pyrite structures. The new phase has fulfilled all the necessary criteria of structural stability and its practical existence. The transition pressure of 8 GPa drives the structural change from pyrite to orthorhombic phase in RuS2. From the thermodynamical calculation, we have reported the stability of new-phase under various ranges of applied pressure and temperature. Further, from the results of phonon dispersion calculated at Zero Point Energy, pyrite structure exhibits ground state stability and the marcasite phase has all modes of frequencies positive. The newly proposed phase is a semiconductor with a band gap comparable to its pyrite counterpart but vary in optical absorption by around 106 cm−1. The various Ru doped structures have also shown similar optical absorption spectra in the same order of magnitude. We have used crystal field theory to explain high optical absorption which is due to the involvement of different electronic states in formation of electronic and optical band gaps. Lӧwdin charge analysis is used over the customarily Mulliken charges to predict 89% of covalence in the compound. Our results indicate the importance of new phase to enhance the efficiency of photovoltaic materials for practical applications.

scholarly journals Dynamical strengthening of covalent and non-covalent molecular interactions by nuclear quantum effects at finite temperature

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Huziel E. Sauceda ◽  
Valentin Vassilev-Galindo ◽  
Stefan Chmiela ◽  
Klaus-Robert Müller ◽  
Alexandre Tkatchenko
Keyword(s):  
Finite Temperature ◽  
Electrostatic Interactions ◽  
Zero Point ◽  
Quantum Effects ◽  
Van Der Waals Interactions ◽  
Interatomic Distances ◽  
Point Energy ◽  
Molecular Bond ◽  
Energy Surfaces ◽  
Nuclear Quantum Effects

AbstractNuclear quantum effects (NQE) tend to generate delocalized molecular dynamics due to the inclusion of the zero point energy and its coupling with the anharmonicities in interatomic interactions. Here, we present evidence that NQE often enhance electronic interactions and, in turn, can result in dynamical molecular stabilization at finite temperature. The underlying physical mechanism promoted by NQE depends on the particular interaction under consideration. First, the effective reduction of interatomic distances between functional groups within a molecule can enhance the n → π* interaction by increasing the overlap between molecular orbitals or by strengthening electrostatic interactions between neighboring charge densities. Second, NQE can localize methyl rotors by temporarily changing molecular bond orders and leading to the emergence of localized transient rotor states. Third, for noncovalent van der Waals interactions the strengthening comes from the increase of the polarizability given the expanded average interatomic distances induced by NQE. The implications of these boosted interactions include counterintuitive hydroxyl–hydroxyl bonding, hindered methyl rotor dynamics, and molecular stiffening which generates smoother free-energy surfaces. Our findings yield new insights into the versatile role of nuclear quantum fluctuations in molecules and materials.

scholarly journals Time-Resolved Measurements and Master Equation Modelling of the Unimolecular Decomposition of CH3OCH2

2020 ◽  
Vol 234 (7-9) ◽  
pp. 1233-1250 ◽  
Author(s):  
Arrke J. Eskola ◽  
Mark A. Blitz ◽  
Michael J. Pilling ◽  
Paul W. Seakins ◽  
Robin J. Shannon
Keyword(s):  
Energy Transfer ◽  
Master Equation ◽  
Rate Coefficient ◽  
Zero Point ◽  
Buffer Gas ◽  
Unimolecular Decomposition ◽  
Time Resolved ◽  
Point Energy ◽  
Wide Range ◽  
Transfer Parameters

AbstractThe rate coefficient for the unimolecular decomposition of CH3OCH2, k1, has been measured in time-resolved experiments by monitoring the HCHO product. CH3OCH2 was rapidly and cleanly generated by 248 nm excimer photolysis of oxalyl chloride, (ClCO)2, in an excess of CH3OCH3, and an excimer pumped dye laser tuned to 353.16 nm was used to probe HCHO via laser induced fluorescence. k1(T,p) was measured over the ranges: 573–673 K and 0.1–4.3 × 1018 molecule cm−3 with a helium bath gas. In addition, some experiments were carried out with nitrogen as the bath gas. Ab initio calculations on CH3OCH2 decomposition were carried out and a transition-state for decomposition to CH3 and H2CO was identified. This information was used in a master equation rate calculation, using the MESMER code, where the zero-point-energy corrected barrier to reaction, ΔE0,1, and the energy transfer parameters, ⟨ΔEdown⟩ × Tn, were the adjusted parameters to best fit the experimental data, with helium as the buffer gas. The data were combined with earlier measurements by Loucks and Laidler (Can J. Chem.1967, 45, 2767), with dimethyl ether as the third body, reinterpreted using current literature for the rate coefficient for recombination of CH3OCH2. This analysis returned ΔE0,1 = (112.3 ± 0.6) kJ mol−1, and leads to $k_{1}^{\infty}(T)=2.9\times{10^{12}}$ (T/300)2.5 exp(−106.8 kJ mol−1/RT). Using this model, limited experiments with nitrogen as the bath gas allowed N2 energy transfer parameters to be identified and then further MESMER simulations were carried out, where N2 was the buffer gas, to generate k1(T,p) over a wide range of conditions: 300–1000 K and N2 = 1012–1025 molecule cm−3. The resulting k1(T,p) has been parameterized using a Troe-expression, so that they can be readily be incorporated into combustion models. In addition, k1(T,p) has been parametrized using PLOG for the buffer gases, He, CH3OCH3 and N2.

Sign in / Sign up

Export Citation Format

Share Document