arXiv subjects

V. V. Flambaum

Publications and source records attributed to V. V. Flambaum.

At least 19 recordsLinked to original sources

arXiv2026

Spin-dependent fermion potentials from mixed tensor couplings of massive spin-1 and spin-2 bosons

Searches for weak spin-dependent forces are commonly interpreted in terms of a basis of sixteen rotationally invariant two-fermion potentials, including potentials which violate parity (P) and time-reversal (T) invariance. We derive finite-range coordinate-space potentials generated by a massive spin-1 boson with vector, axial-vector, tensor, and pseudotensor couplings to Dirac fermions. In addition to the familiar vector--vector, vector--axial-vector, and axial-vector--axial-vector interactions, we obtain the mixed vector--tensor, vector--pseudotensor, axial-vector--tensor, and axial-vector--pseudotensor potentials, together with tensor--tensor, tensor--pseudotensor, and pseudotensor--pseudotensor terms. We retain the contact terms needed in atomic-scale applications and give compact expressions that include both orderings of inequivalent fermion vertices. We then extend the analysis to a massive spin-2 mediator described by a symmetric Fierz--Pauli field. Besides the conventional coupling to the conserved fermion energy--momentum tensor, we consider a symmetric axial-tensor current. Its nonconservation for massive fermions makes the longitudinal spin-2 helicities contribute to axial-tensor--axial-tensor exchange. The leading minimal spin-2 interactions are either P,T even or P odd and T even; in particular, they do not generate a T-odd potential. We map the resulting interactions onto the sixteen-potential Dobrescu--Mocioiu basis and use this mapping to translate existing experimental constraints into numerical limits on spin-1 and spin-2 coupling products in the small- and large-mediator-mass regimes, together with representative limits at finite mediator masses. The derived relations between the boson-exchange coupling constants and the coefficients of the basis potentials also allow published exclusion curves to be rescaled to arbitrary mediator masses.

hep-ph↗

arXiv2026

Relative enhancement of low-mass vector-boson exchange in higher waves matrix elements: parity non-conservation in hydrogen

Models of unification predict additional $Z'$ boson, which contributes to parity non-conservation (PNC) in atoms. If $Z'$ boson is light, ratio of $Z'$ boson contribution to the Standard Model $Z$ boson contribution to atomic PNC increases with decreasing nuclear charge $Z$ faster than $1/Z^2$. This motivated our previous study of PNC in hydrogen and deuterium proportional to the weak interaction matrix elements $ $. An enormous additional relative enhancement appears in the matrix elements between higher waves, such as $ $, since $p_{3/2}$ and $d_{3/2,5/2}$ wave functions vanish at $r \to 0$, suppressing matrix elements of the contact $Z$ boson mediated contact electron-nucleus interaction. Measurements of $ $ will simplify disentanglement of the $Z'$ contribution from the Standard Model background.

hep-ph↗

arXiv2026

Calculation of the energy levels and hyperfine structure for Xe~II, Rn~II, and Og~II ions

Energy levels, Land\'e $g$-factors, and hyperfine-structure constants are calculated for the singly ionized noble-gas atoms Xe II, Rn II, and Og II. The calculations are performed using the configuration-interaction method with perturbative treatment of high-lying configurations. Core polarization effects in the hyperfine interaction are included within the time-dependent Hartree-Fock method. Calculations for Xe II are used to test the accuracy of the approach by comparison with available experimental data. The agreement is at the level of about one percent for the energies and typically about ten percent for the hyperfine constants, with better accuracy for states with large hyperfine constants. Predictions are then presented for Rn II and Og II, for which experimental spectroscopic data are limited or absent. Special attention is paid to Breit and quantum-electrodynamic corrections to the hyperfine structure in heavy many-electron ions. We show that these corrections may be strongly enhanced by configuration mixing when interacting states with very different hyperfine matrix elements are separated by small energy intervals. This effect is demonstrated explicitly for odd-parity $J=1/2$ states of Og II. The calculated hyperfine-structure constants for Rn II and Og II provide electronic factors needed for extracting nuclear magnetic dipole and electric quadrupole moments from future spectroscopic measurements. These results may be useful for experimental studies of radon and oganesson ions and for testing nuclear models in the superheavy region.

physics.atom-ph↗

arXiv2026

Signatures of gravity-mediated dark matter interaction in theories with large extra dimensions

Dark matter particles that couple to the Standard Model only through gravity are usually regarded as inaccessible to laboratory detection. This expectation can change in theories with $n$ extra spatial dimensions, where gravity is enhanced at short distances and the potential scales as $1/r^{1+n}$. We reconsider the gravity-mediated dark matter (DM) interactions in Arkani-Hamed-Dimopoulos-Dvali (ADD) models with $n$ large extra dimensions. The cumulative exchange of the gravitational Kaluza-Klein (KK) modes leads to the effective strength of interactions with the Standard Model nucleons that scales as $m_pm_\chi M_*^{-4}$, where $ m_\chi$ is the mass of DM and $M_*$ is the fundamental $4+n$ dimensional mass scale. We confront this interaction with sensitivity achieved in the large Xe-based underground direct detection experiments and derive bounds on the $\{m_\chi,M_*\}$ parameter space that stretches all the way to $M_*\sim$ few TeV. We also address the indirect detection of scalar $\chi$ that can resonantly annihilate via the on-shell KK modes into the SM particles $W^\pm,Z,h$. The annihilation cross section for the process scales as $\langle\sigma v\rangle \sim m_\chi^nM_*^{-n-2}$, and stringent limits on the same parameter space can be derived from observations of high-energy galactic $\gamma$ rays.

hep-ph↗

arXiv2026

Parity non-conservation in isotope chain of tin

We calculate parity non-conservation (PNC) amplitudes for all magnetic-dipole (M1) transitions within the ground $5p^2$ configuration of Sn, including the standard model interaction and contribution of a hypothetical additional $Z'$-boson. Among the transitions considered, the $^1$S$_0$-$^3$P$_1$ transition has the largest PNC amplitude and appears to be the most promising candidate for an experiment. We also discuss a measurement method capable of achieving unprecedentedly high precision in a measurement of PNC in this transition. We argue that the most robust test should be based on ratios of PNC amplitudes for different isotopes, since the atomic-structure factor largely cancels in such ratios. We study the effect of the neutron skin on these isotope ratios using available nuclear data for Sn and show that the uncertainty associated with the neutron skin can be reduced to the $10^{-4}$ level relative to the isotopic variation of the PNC effect. Our results indicate that PNC measurements along a chain of Sn isotopes offer a realistic and sensitive probe of new physics.

physics.atom-ph↗

arXiv2026

Shielded inner-shell transitions in atomic samarium for tests of fundamental physics

Forbidden atomic transitions provide some of the most stringent low-energy tests of physics beyond the Standard Model, with sensitivity set by the interplay between the sought-for signals and systematics suppressed by symmetry. Here we identify the previously unobserved $4f^{6}6s^{2}\,{}^{5}$D$_{0}$ level of neutral samarium at $14\,564.90(2)\,\mathrm{cm}^{-1}$, opening the ${}^{7}$F$_{0}\rightarrow{}^{5}$D$_{0}$ inner-shell transition for precision spectroscopy. Candidate lines extracted from dual-comb absorption spectra were assigned using double-resonance population-depletion and sequential-excitation measurements. The observed pressure broadening, $0.12(2)\,\mathrm{MHz/torr}$, and pressure shift, $-0.145(4)\,\mathrm{MHz/torr}$, indicate an inner-shell $4f$-transition shielded from external perturbations. Many-body calculations predict a metastable lifetime in the range $120$-$200\,\mathrm{ms}$, corresponding to a quality factor of order $\mathcal{Q}\sim10^{14}$, large sensitivity coefficients for variation of the fine-structure constant, and a nuclear-spin-dependent parity-violation amplitude comparable to that of cesium. Crucially, the $J=0\rightarrow J=0$ selection rule suppresses by symmetry both the nuclear-spin-independent parity-violation channel and the M1 and E2 backgrounds that complicated previous heavy-atom experiments, yielding a uniquely clean window onto the nuclear anapole moment. The two stable spin-$7/2$ isotopes of samarium provide a remarkable opportunity to largely cancel atomic-structure uncertainties by measuring the ratio of parity-violation effects in the two isotopes. These results establish neutral samarium as a platform for inner-shell precision spectroscopy and tests of physics beyond the Standard Model.

physics.atom-ph↗

arXiv2026

Parity Nonconservation in Hydrogen Induced by Low-Mass Vector-Boson Exchange

Parity-nonconserving (PNC) effects in atoms produced by $Z$-boson exchange between the electron and the nucleus grow rapidly with the nuclear charge $Z$. If a hypothetical additional $Z'$ boson is light, however, its contribution does not exhibit the same strong enhancement with $Z$. As a result, the ratio of the low-mass $Z'$ contribution to the Standard Model $Z$-boson contribution increases rapidly with decreasing $Z$, in fact faster than $1/Z^2$. Hydrogen has a further important advantage: its theoretical description is substantially cleaner than that of heavy atoms, allowing a more accurate interpretation of experimental results. For these two reasons, hydrogen and deuterium PNC experiments may provide an especially favorable setting in which to disentangle a possible $Z'$ contribution from the Standard Model background. In this paper we calculate the ratio of the $Z'$-boson contribution, for arbitrary $Z'$ mass, to the Standard Model $Z$-boson contribution to parity violation in hydrogen and deuterium, including both nuclear-spin-independent (NSI) and nuclear-spin-dependent (NSD) interactions.

hep-ph↗

arXiv2026

Effects of dispersion parity-violating interaction in electron scattering and atoms

Exchange of two neutrinos (as well as other fermions) generates a long-range parity-violating potential of the form $\sim G^2/r^5$, with characteristic range $\hbar/(2m_\nu c)$. In atomic systems the corresponding matrix elements converge at distances $r < 10/M_Z$, so that the interaction between electron and quarks effectively reduces to a contact term $\sim G^2 M_Z^2 \delta^{3}(\vec{r}) \sim G\,\alpha\,\delta^{3}(\vec{r})$. This interaction produces a $-0.8\%$ correction to the effective weak charge of cesium, resolving the $2\sigma$ discrepancy between the Standard Model prediction and the measured Cs parity-violation amplitude. The corresponding value of the weak mixing angle is $\sin^2\theta_W = 0.2375(19)$ at $q^2 \approx 0$, in agreement with the Standard Model prediction $\sin^2\theta_W = 0.23873$. The relative correction to the proton weak charge is about $3\%$. Using these results, we revisit the limits on an additional $Z'$ boson and obtain a constraint on isospin-conserving oblique radiative corrections characterized by the Peskin--Takeuchi parameter $S = -0.32(53)$ at $q^2 \approx 0$.

hep-ph↗

arXiv2025

Collapse of Coulomb Bound States of Vector Bosons

Charged spin 1 (vector) particles behave very differently from electrons or scalars in a Coulomb field. For an infinitely heavy point-like nucleus their bound state wave functions fall to the centre, and embedding the system in a renormalisable electroweak-type theory does not remedy this short-distance pathology. We therefore solve the pure Coulomb problem for a finite nuclear radius $R$ and recover the point nucleus limit by letting $R\to 0$. This approach allows us to include the crucial Upsilon term in the wave equations, which for the point-like nucleus is proportional to delta(r) and was ignored in the previous calculations of the energy spectrum. Several unusual effects emerge: (i) The Upsilon term supports a tower of states located mainly inside the nucleus. As R -> 0 their number diverges, most lying in the negative energy continuum (energy epsilon < - m c^2). They trigger vacuum breakdown - particle-antiparticle pair creation that ultimately screens the nuclear charge. (ii) Ordinary Sommerfeld-like states (with binding energy smaller m c^2) persist, but a finite fraction of each wave function leaks into the nucleus, even as R -> 0. (iii) Charge density of a negatively charged vector particle changes sign in a vicinity of the nucleus and becomes positive charge density, whereas the Upsilon term ensures its density inside the nucleus remains negative. (iv) For weak coupling, Z alpha << 1, yet with mR <Z alpha, the non-relativistic solution differs qualitatively from Schrodinger theory despite binding energies are well below m c^2; agreement is recovered only when Z alpha << mR. These phenomena highlight the distinctive and subtle behaviour of spin-1 particles in the Coulomb field.

hep-ph↗

arXiv2025

Parity Nonconservation in Rb and Sr$^+$ due to Low-Mass Vector Boson

We calculate the parity non-conserving (PNC) electric-dipole ($E1$) transition amplitudes for the $5s - 6s$ and $5s - 4d_{3/2}$ transitions in Rb and Sr$^+$. Our results include both the nuclear-spin-independent and nuclear-spin-dependent contributions, with particular emphasis on the potential effects of a hypothetical additional $Z'$-boson. We highlight possible advantages of using light atoms in searches for such new interaction. The ratio of the contribution of a low mass $Z'$-boson to the contribution of the Standard model $Z$ -boson to PNC effects increases rapidly (faster than $1/Z^2$) with decreasing nuclear charge $Z$. Another advantage is that theoretical interpretations of experiments in lighter systems may be carried out with a higher accuracy than that in Cs, Ba$^+$, Fr and Ra$^+$.

physics.atom-ph↗

arXiv2025

Oscillations of dark matter halos in galaxies and their effects on motion of stars

Matter and dark matter in galaxies represent two main components linked by the gravitational interaction. Collisions of galaxies may create an offset between the centers of mass of these components. Ignoring internal dynamics of particles in the dark matter halo and Keplerian rotations of matter in the galaxy, we focus on possible relative oscillations of the matter in the dark matter halo. This two-fluid model is somewhat similar to the ``giant dipole resonances'' in nuclei. We estimate possible amplitude and frequency of such oscillations assuming that the offset of the centers of mass is small as compared with the size of the galaxy. Such oscillations, if exist, should manifest themselves in anomalies of velocities of stars in the galaxy, such as the density waves and runaway stars which have orbit periods in resonance with oscillations.

astro-ph.GA↗

arXiv2025

Hf$^{12+}$ ion: Highly Charged Ion for Next-Generation Atomic Clocks and Tests of Fundamental Physics

We use advanced computational techniques to study the electronic structure of the Hf$^{12+}$ ion, with the goal of assessing its potential for use in highly accurate atomic optical clocks and search for new physics. Such clocks should combine low sensitivity to external perturbations with high sensitivity to a possible time variation of the fine-structure constant $\alpha$. The system features two clock transitions. One is an $f-p$ transition in terms of single-electron states, which exhibits strong sensitivity to variations in $\alpha$. The other is an electric-quadrupole (E2) transition between states of the ground-state configuration, which can serve as an anchor transition for measuring one frequency against the other. All three relevant states possess very small and nearly equal static dipole polarizabilities, resulting in an extremely small blackbody-radiation shift. The quadrupole shift is also small and can be further suppressed. Altogether, Hf$^{12+}$ appears to be a highly promising candidate for both precision timekeeping and searches for new physics.

physics.atom-ph↗

arXiv2025

Enhancement of Weak Interactions in Phase Transitions in Condensed Matter and Early Universe

Parity-violating weak interactions produce extremely small energy differences between left- and right-handed chiral systems. We show that these microscopic effects may be strongly amplified during collective phenomena such as phase transitions. The enhancement factor is proportional to the critical number of atoms, $N_c$, in the nucleus of the new phase. After the nucleus reaches its critical size, it grows until it fills the entire system. Measurement of the ratio of produced left and right chiral structures may provide a way to measure this critical number $N_c$. Experiments where definite spin-chiral structures are formed during a phase transition in crossed electric and magnetic fields, indicate $N_c \sim 10^9 - 10^{10}$. An open question is whether a similar enhancement could operate during cosmological phase transitions - thereby boosting CP-violating effects sufficiently to contribute to the observed baryon-to-photon ratio.

hep-ph↗

arXiv2025

Constraints on the Variation of the QCD Interaction Scale $\Lambda_{\text{QCD}}$

Laboratory and astrophysical tests of ''constant variation'' have so far concentrated on the dimensionless fine-structure constant $\alpha$ and on the electron or quark mass ratios $X_{e,q}=m_{e,q}/\Lambda_{\text{QCD}}$, treating the QCD scale $\Lambda_{\text{QCD}}$ as unchangeable. Certain beyond Standard Model frameworks, most notably those with a dark matter or dark energy scalar field $\phi$ coupling with the gluon field, would make $\Lambda_{\text{QCD}}$ itself time dependent while leaving $\alpha$ and the electron mass untouched. Under the minimal assumption that this gluonic channel is the sole $\phi$ interaction, we recast state-of-the-art atomic clock comparisons into $\dot{\Lambda}_{\text{QCD}}/\Lambda_{\text{QCD}}=(3.2 \pm 3.5) \times 10^{-17} \ \text{yr}^{-1}$ limits, translate the isotope yields of the 1.8-Gyr-old Oklo natural reactor into a complementary geophysical limit of $|\delta\Lambda_{\text{QCD}}/\Lambda_{\text{QCD}}|<2\times10^{-9}$ over that time span, corresponding to the linear drift limit $|\dot{\Lambda}_{\text{QCD}}/\Lambda_{\text{QCD}}|<1\times10^{-18} \text{yr}^{-1}$, and show that the proposed $8.4$ eV $^{229}$Th nuclear clock would amplify a putative $\Lambda_{\text{QCD}}$ drift by four orders of magnitude compared with present atomic clocks. We also obtain constraints from quasar absorption spectra and Big Bang Nucleosynthesis data.

hep-ph↗

arXiv2025

Isotope shift for total electron binding energy of atoms

We compute the isotope shifts of the \emph{total} electron binding energy of neutral atoms and singly charged ions up to element $Z=120$, using relativistic Hartree-Fock method including the Breit interaction. Field shift coefficients are extracted by varying the nuclear charge radius; a small quadratic term is retained to cover large radius changes relevant to superheavy nuclei. We tabulate isotope shift coefficients for closed shell systems from Ne to Og and benchmark selected open shell cases, used to test the interpolation formula. A simple power law interpolation $bZ^k$ reproduces calculated field shifts to within about 1\% across the table, with the effective exponent $k$ growing from roughly 5 near $Z \sim 50$ to about 12 at $Z \sim 118$. Due to the domination of inner shells, differences between neutrals and singly charged ions does not exceed few percent, becoming noticeable mainly when an outer $s$ electron is removed. Therefore, these results may also be used for higher charge ions.

physics.atom-ph↗

arXiv2025

Ionisation potentials and energy levels of ions of heavy and superheavy elements Te, I, Po, At, Lv and Ts

We calculate the energy levels and successive ionisation potentials (IPs) of ions of the three heaviest known Group 16 and 17 elements using a theoretical approach that combines the linearised coupled-cluster method, configuration interaction, and perturbation theory. Our calculations address critical gaps in the available data on the electronic structure of the superheavy elements livermorium (Lv) and tennessine (Ts), as well as their lighter homologues polonium (Po) and astatine (At). To assess the accuracy of our methods, we perform analogous calculations for the lighter homologues tellurium (Te) and iodine (I), for which both experimental and reliable theoretical data are available for comparison.

physics.atom-ph↗

arXiv2025

Further steps towards next generation of covariant energy density functionals

The present study aims at further development of covariant energy density functionals (CEDFs) towards more accurate description of binding energies across the nuclear chart. For the first time, infinite basis corrections to binding energies in the fermionic and bosonic sectors of the covariant density functional theory have been taken into account in the fitting protocol within the covariant density functional theory. In addition, total electron binding energies have been used in the conversion of atomic binding energies into nuclear ones. Their dependence on neutron excess has been investigated for the first time across the nuclear chart within atomic approach. These factors have been disregarded in previous generation of covariant energy density functionals but their neglect leads to substantial global calculation errors for physical quantities of interest. For example, these errors for binding energies are of the order of 0.8 MeV or higher for the three major classes of covariant energy density functionals.

nucl-th↗

arXiv2025

Electronic structure calculation for superheavy elements Livermorium (Lv, Z=116) and Tennessine (Ts, Z=117) and their lighter analogs Te, I, Po, and At

Advanced theoretical techniques that combine the linearized coupled-cluster method, configuration interaction method, and perturbation theory are used to calculate energy levels, ionization potentials, electron affinities, field isotope shift, and static dipole polarizabilities of the superheavy elements Lv and Ts, along with their lighter analogs Te, I, Po, and At. Calculations for the heavy elements, Po, At, Lv, and Ts are used to address the gaps in the experimental data. Calculations for the lighter elements, Te and I (and partly Po and At) are used to demonstrate the accuracy of the calculations.

physics.atom-ph↗