Exclusion Principle Violating Research Articles

Strongest Atomic Physics Bounds on Noncommutative Quantum Gravity Models.

Investigations of possible violations of the Pauli exclusion principle represent critical tests of the microscopic space-time structure and properties. Space-time noncommutativity provides a class of universality for several quantum gravity models. In this context the VIP-2 lead experiment sets the strongest bounds, searching for the Pauli exclusion principle violating atomic transitions in lead, excluding the θ-Poincaré noncommutative quantum gravity models far above the Planck scale for nonvanishing θ_{μν} electriclike components, and up to 6.9×10^{-2} Planck scales if θ_{0i}=0.

Tests of Pauli exclusion principle violations from noncommutative quantum gravity

We review the main recent progresses in noncommutative space–time phenomenology in underground experiments. A popular model of noncommutative space–time is [Formula: see text]-Poincaré model, based on the Groenewold–Moyal plane algebra. This model predicts a violation of the spin-statistic theorem, in turn implying an energy and angular dependent violation of the Pauli exclusion principle. Pauli exclusion principle violating transitions in nuclear and atomic systems can be tested with very high accuracy in underground laboratory experiments such as DAMA/LIBRA and VIP(2). In this paper we derive that the [Formula: see text]-Poincaré model can be already ruled-out until the Planck scale, from nuclear transitions tests by DAMA/LIBRA experiment.

Screened Exchange Corrections to the Random Phase Approximation from Many-Body Perturbation Theory.

The random phase approximation (RPA) systematically overestimates the magnitude of the correlation energy and generally underestimates cohesive energies. This originates in part from the complete lack of exchange terms that would otherwise cancel Pauli exclusion principle violating (EPV) contributions. The uncanceled EPV contributions also manifest themselves in form of an unphysical negative pair density of spin-parallel electrons close to electron-electron coalescence. We follow considerations of many-body perturbation theory to propose an exchange correction that corrects the largest set of EPV contributions, while having the lowest possible computational complexity. The proposed method exchanges adjacent particle/hole pairs in the RPA diagrams, considerably improving the pair density of spin-parallel electrons close to coalescence in the uniform electron gas (UEG). The accuracy of the correlation energy is comparable to other variants of second-order screened exchange (SOSEX) corrections although it is slightly more accurate for the spin-polarized UEG. Its computational complexity scales as [Formula: see text] or [Formula: see text] in orbital space or real space, respectively. Its memory requirement scales as [Formula: see text].

New Limits on Bosonic Dark Matter, Solar Axions, Pauli Exclusion Principle Violation, and Electron Decay from the Majorana Demonstrator

We present new limits on exotic keV-scale physics based on 478kg d of Majorana Demonstrator commissioning data. Constraints at the 90%confidence level are derived on bosonic dark matter (DM) and solar axion couplings, Pauli exclusion principle violating (PEPV) decay, and electron decay using monoenergetic peak signal limits above our background. Our most stringent DM constraints are set for 11.8keV mass particles, limiting g_{Ae}<4.5×10^{-13} for pseudoscalars and (α^{'}/α)<9.7×10^{-28} for vectors. We also report a 14.4keV solar axion coupling limit of g_{AN}^{eff}×g_{Ae}<3.8×10^{-17}, a 1/2β^{2}<8.5×10^{-48} limit on the strength of PEPV electron transitions, and a lower limit on the electron lifetime of τ_{e}>1.2×10^{24} yr for e^{-}→ invisible.

Ability of a coupled electron pair approximation to treat single bond breakings

The self-consistent size-consistent CI ((SC) 2CI), which considers all exclusion principle violating (EPV) diagrams, is able to treat single bond breakings, despite its single-reference character. It is shown here that a CEPA-3 (coupled electron pair approximation) dressing, considering only the EPVs through the occupied molecular orbitals, treats satisfactorily the single bond breaking processes, while the uniform dressings, e.g. CEPA-0, the averaged coupled pair functional (ACPF) or averaged quadratic coupled cluster (AQCC) lead to non-convergence or spurious energy lowering in such processes. A number of test calculations illustrate this rationalizable feature.

On the Size Consistency of Multireference CEPA Methods

The size consistency of various multireference coupled electron pair approaches (MRCEPA) is analysed. These methods include the MRCEPA0, MR averaged coupled pair functional (MR-ACPF), MR averaged quadratic coupled cluster (MR-AQCC), MR (singles and doubles) CEPA (MRDCEPA) and the recently proposed MR averaged CEPA (MR-ACEPA) methods. Test calculations on the O2 dimer show that a correct treatment of the variationally included (VI) terms such as in the MRDCEPA and MR-ACEPA methods is necessary for obtaining nearly size-consistent results. On the other hand, the results strongly suggest that it is impossible to obtain exact size consistency with any method employing the diagonal shift formalism. The analysis also shows that the size consistency error is not significantly affected by the exclusion principle violating (EPV) terms.

New Versions of Approximately Extensive Corrected Multireference Configuration Interaction Methods

In a previous paper (Szalay,P. G.; Bartlett, R. J. J. Chem. Phys. 1995, 103, 3600) we reviewed all approximately extensive corrected multireference configuration interaction (MR-CI) methods and also proposed a new method called the multireference averaged quadratic coupled-cluster (MR-AQCC) method. In this paper we continue the investigation of these methods and propose new variants by including the effect of (a) virtual orbitals in the EPV (exclusion principle violating) contributions, (b) redundancies due to the MR nature of the reference space. Results of test calculations on water, Be2, Be/H2, ozone and NO2/HF systems are presented which show that these new methods are able to describe potential energy surfaces very accurately even if small, but qualitatively correct, reference spaces are used.

Alternative ans�tze in coupled-cluster theory. IV. Comparison for the two electron problem and the role of exclusion principle violating (EPV) terms

The two-electron problem is investigated using exponentially parametrized wave functions for various different coupled-cluster (CC) methods, including regular, expectation value, symmetrized expectation value (i.e., unitary), extended, and quadratic configuration interaction (CI) variants. All are viewed as arising from alternative energy functionals. This pedagogical evaluation demonstrates the differences in these methods, including the role of EPV terms. © 1992 John Wiley & Sons, Inc.

Improving the convergence of the many-body perturbation expansion through a convenient summation of exclusion principle violating diagrams

All fourth-order and some higher-order EPV (exclusion principle violating) diagrams may be summed up through a simple modification of the energy denominators in the second-order corrections. The procedure simply requires supplementary arrays of dimension N3 (N being the number of orbitals). The typical divergence of the second-order corrections for near-degeneracy cases, occuring for bond lengthenings, is slowed down; the improvement is especially clear for the Epstein–Nesbet partition of the Hamiltonian. The ground state spectroscopic constants are improved as shown on Li2, Li4, N2, and H2O; the procedure may also be used in chemical reaction studies. The above correction results in a straightforward improvement of the Davidson’s correction, which is known to overestimate the effect of quadruple excitations.

Comments on the exclusion‐principle‐violating diagrams cancellation in correlations energy calculation by many‐body Rayleigh–Schrödinger perturbation theory

AbstractWhen calculating the correlation energy where the effect of higher than double excitations is included by means of many‐body Rayleigh–Schrödinger perturbation theory (MB‐RSPT) through fourth order the problem of cancellation of exclusion‐principle‐violating (EPV) diagrams arises. The cancellation of EPV diagrams in fourth order of MB‐RSPT is demonstrated for diagrams which include the effect of tetraexcitations.

Electronic structure of ferromagnetic hcp cobalt. III. Magnetic hyperfine field

Using the energy bands and wave functions of ferromagnetic cobalt from a self-consistent hybridized tight-binding---orthogonalized-plane-wave ferromagnetic band calculation, we have obtained the core and the band contributions to the hyperfine field at the cobalt nucleus to be, respectively, -380.1 and -42.7 kOe. The core contribution of -380.1 kOe, in the moment-perturbation (MP) approach, is composed of contributions from $1s$, $2s$, and $3s$ cores, respectively, of -0.07, -272.4, and -107.7 kOe. These values have been transformed to derive the results that would be expected from a unrestricted-Hartree-Fock (UHF) theory, for the core states and give the individual contributions, in order, from $1s$, $2s$, and $3s$ states as -19.0, -528.1, and +154.6 kOe which add up to about the same total core contribution. The most important effect, causing the individual core contributions to differ substantially in the two methods, is shown to result from exclusion-principle-violating (EPV) diagrams. The small difference of the total core contributions from the MP and the UHF approaches arises from EPV diagrams in which the band electrons are involved. The negative band contribution to the hyperfine field is found to arise from the paired $3d$-like and free-like band states, which overwhelm the positive contribution from the unpaired-spin electrons in the majority-spin band. Arguments are proposed to show that the difference between the theoretical value -422.9 kOe for the hyperfine field and the experimental value of -223.0 could arise from the influence of correlation effect on the $3d$-like band electron wave functions, particularly those at the Fermi surface.

Many-body calculation of the atomic hyperfine coupling constant: The lithium atom

The atomic hyperfine coupling constant of the lithium atom in the 2S ground state is calculated by taking into account a correlation based on the wavefunctions of Clementi, Roothaan, and Yoshimine, including higher−order Exclusion−Principle−Violating (EPV) diagrams of first and second kind. The result is 2.91±0.02 a. u., compared with the experimental value 2.9096. Detailed comparison is made with the work by Chang, Pu, and Das who have calculated the coupling constant as 2.89±0.02 a. u. According to the comparison with the work of Chang et al., there is good agreement between individual diagrams, considering the difference in potentials used and the total result, the small difference in the latter being due to the higher order EPV diagrams effect considered by the present calculation.

Approximation Methods in Many-Body Perturbation Theory

An analysis of some approximations common in the treatment of many-body systems indicates that the inclusion of large numbers of uncancelled exclusion-principle-violating (EPV) processes leads to meaningless results. We therefore propose as a criterion for the validity of many-body approximations that there should be no such large-scale inclusion of EPV processes. The graphs generated in the BCS theory are analyzed from this point of view.