arXiv subjects

V. V. Flambaum

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

At least 37 records · Page 2Linked to original sources

arXiv2025

Microscopic composite systems bound by strong gravity in extra dimensions as candidates for dark matter

In the Arkani-Hamed-Dimopoulos-Dvali (ADD) model with n extra compactified dimensions, the gravitational potential scales as 1/r^{n+1} and becomes significantly stronger at short distances. We investigate the possibility of forming small-sized composite systems of Standard Model particles bound by this potential. Such bound states, composed of quarks, neutrinos, axions, or other particles, exhibit a small cross-section-to-mass ratio, making them viable candidates for dark matter.

hep-ph↗

arXiv2025

Enhanced nuclear Schiff and electric dipole moments in nuclei with an octupole deformation

Deformed nuclei exhibit enhanced moments that violate time-reversal invariance ($T$) and parity ($P$). This paper focuses on the enhanced nuclear electric dipole moment (EDM) and Schiff moment present in nuclei with octupole deformation (pear-shaped nuclei). These moments, which are proportional to the octupole deformation, have a collective nature and are large in the intrinsic frame that rotates with the nucleus. However, in a state with definite angular momentum and parity, $T$ and $P$ conservation forbid their expectation values in the laboratory frame, as nuclear rotation causes them to vanish. In nuclei with octupole deformation, close opposite-parity rotational states with identical spin are mixed by $T$,$P$-violating nuclear forces. This mixing polarises the nuclear axis along the nuclear spin, allowing moments from the intrinsic frame to manifest in the laboratory frame, provided the nuclear spin $I$ is sufficiently large. Using half-life data for $E1$ transitions from the NuDat database, we calculate the intrinsic nuclear EDM $d_{\text{int}}$ for a range of nuclei theorised to exhibit octupole deformation. From these values, we independently estimate the intrinsic nuclear Schiff moment $S_{\text{int}}$ and the octupole deformation parameter $β_{3}$. Finally, we compare the magnitude of these collective moments in the laboratory frame with the contributions from valence nucleons, providing an estimate of the nuclear EDM and Schiff moment components unrelated to octupole deformation. The uncertainty of our estimates may exceed a factor of 10.

nucl-th↗

arXiv2025

Nuclear clock based on the Th V ion

We propose that a nuclear clock based on the Th V ion can surpass the accuracy of clocks built with other thorium ions. The Th$^{4+}$ ion has a rigid closed-shell core with zero total electron angular momentum, suppressing frequency shifts from black-body radiation and stray external fields that act mainly on electrons. We calculate the energy shift of the nuclear clock transition frequency in $^{229}$Th due to the Coulomb field of atomic electrons and find a relative frequency difference of $2.8 \times 10^{-7}$ between Th IV and Th V - twelve orders of magnitude larger than the projected $10^{-19}$ fractional uncertainty of a nuclear clock. We also perform calculations for Th V energy levels, ionization potential, static polarizability, and the black-body radiation shift of the nuclear line. Additionally, we determine the nuclear transition frequencies in two thorium ions and neutral atom: $ω_N=2,020,406.964(70)$ GHz in Th III, $ω_N=2,020,408.264(100)$ GHz in Th II, and $ω_N=2,020,408.364(100)$ GHz in Th I.

physics.atom-ph↗

arXiv2025

Using the Th III Ion for a Nuclear Clock and Searches for New Physics

The 229Th nucleus possesses a unique low-frequency transition at 8.4 eV, which is being considered for the development of an extremely accurate nuclear clock. We investigate an electronic bridge process in the Th III ion, where nuclear excitation occurs via electronic transitions, and demonstrate that a proper choice of laser frequencies can lead to 10,000 enhancement of this effect. Electrons also reduce 1.7 times the lifetime of the nuclear excited state. Additionally, the electronic structure of the Th III ion exhibits features that make it particularly useful for probing new physics. Notably, it contains a metastable state connected to the ground state via a weak M2 transition, which can be utilized for quantum information processing, as well as searches for oscillating axion field, violation of local Lorentz invariance, test of the Einstein's equivalence principle, and measurement of nuclear weak quadrupole moment. The electronic states of the ion present a unique case of level crossing involving the 5f, 6d, and 7s single-electron states. This crossing renders the transition frequencies highly sensitive to potential time-variation of the fine-structure constant.

physics.atom-ph↗

arXiv2025

Resonance nuclear excitation of the $^{229}$Th nucleus via electronic bridge process in Th~II

The 8.4 eV transition in the $^{229}$Th nucleus is the basis for a high-precision nuclear clock with exceptional sensitivity to new physics effects. We have identified several cases in the Th$^+$ ion where electronic excitations closely resonate with the nuclear excitation, with the smallest energy difference being $Δ= -0.09$ cm$^{-1}$. We investigate the electronic bridge process, in which nuclear excitation is induced via electronic transitions, and demonstrate that a proper selection of laser frequencies can lead to a dramatic enhancement of this effect. Additionally, we show that the interaction with electrons significantly shortens the lifetime of the nuclear excited state.

physics.atom-ph↗

arXiv2025

Calculation of the correlation, relativistic and QED corrections to the total electron binding energy in atoms and their nuclear charge dependence

We present relativistic many-body calculations of total electron binding energy of neutral atoms up to element $Z=120$. Binding energy for ions may be found by subtracting known ionization potentials. Accuracy of the results for $17 105$ there). We fit numerical results for binding energies by analytical function of $Z$. We also calculate numerical values and determine dependence on $Z$ of the correlation corrections, Dirac and Breit relativistic corrections and quantum electrodynamics (QED) corrections.

physics.atom-ph↗

arXiv2025

Manifestation of antiquark nuggets in collisions with the Earth

Antiquark nuggets are hypothetical compact composite objects conjectured to account for a significant fraction of dark matter in the Universe. In contrast to quark nuggets, these objects consist of antimatter. They may remain undetected if they possess a sufficiently small cross section relative to their mass. In this paper, we investigate the allowed region in the parameter space of this model that is consistent with the observed neutrino flux from the Sun and the Earth, and the non-observation of seismic events with specific signatures of dark matter particles. We found the allowed values of the antibaryon charge number in this model to be in the interval $2\times 10^{24} 10^{33}$, are not fully excluded by the present study, we show that they conflict with the non-observation of rare catastrophic explosion-like events on the Earth.

hep-ph↗

arXiv2024

Absolute frequency measurements on the $5s5p^{3}$P$_{0}\to5s6d^{3}$D$_{1}$ transition in strontium

We report the first absolute frequency measurements for the $5s5p^{3}$P$_{0}\to5s6d^{3}$D$_{1}$ transition at 394 nm for all the stable strontium isotopes by utilizing repumping induced spectroscopy in a magneto-optical trap. Absolute transition frequency is measured to be 760524409251(25) kHz for $^{88}$Sr.With reference to $^{88}$Sr, the isotope shifts are measured to be 91052(35), 54600(33), and 51641(28) kHz for $^{84}$Sr, $^{86}$Sr, and $^{87}$Sr, respectively. We calculate the hyperfine constants A and B for the fermionic isotope $^{87}$Sr at kHz level. Furthermore, we perform King plot analysis by combining isotope shifts on the 689-nm transition to our data.

physics.atom-ph↗

arXiv2024

Captured molecules could make a Bose star visible

A Bose star passing through cold molecular clouds may capture atoms, molecules and dust particles. The observational signature of such an event would be a relatively small amount of matter that is gravitationally bound. This binding may actually be provided by invisible dark matter forming the Bose star. We may expect a relative excess of heavier atoms, molecules, and solid dust compared to the content of giant cold molecular clouds since the velocity of heavy particles at a given temperature is lower and it may be small compared to the escape velocity, $v_\mathrm{rms} = \sqrt{3k_\mathrm{B} T/m_\mathrm{gas}} \ll v_\mathrm{esc}=\sqrt{2GM/R}$. Finally, the velocity of this captured matter cloud may correlate with the expected velocity of free dark matter particles (e.g. expected axion wind velocity relative to Earth).

hep-ph↗

arXiv2024

Limits on scalar dark matter interactions with particles other than the photon via loop corrections to the scalar-photon coupling

There is limited information about the interaction strength of a scalar dark matter candidate with hadrons and leptons for a scalar particle mass exceeding $10^{-3}$ eV while its interaction with photon is well studied. The scalar-photon coupling constant receives quantum corrections from one-loop Feynman diagrams which involve the scalar-lepton, scalar-quark, and scalar-W boson vertices. We calculate these one-loop quantum corrections and find new limits on the scalar particle interactions with electron, muon, tau, quarks, nucleons, gluons, Higgs, and W bosons by re-purposing the results of experiments measuring the scalar-photon interaction. Limits on interactions of heavy leptons and quarks have been obtained for the first time, and limits on other interactions in certain mass intervals are 2 to 15 orders of magnitude stronger than those presented in previous publications and exclude the resolution of the muon $g-2$ anomaly with scalar particle.

hep-ph↗

arXiv2024

Constraints on the Variation of Physical Constants, Equivalence Principle Violation, and a Fifth Force from Atomic Experiments

The aim of this paper is to derive limits on various forms of ``new physics'' using atomic experimental data. Interactions with dark energy and dark matter fields can lead to space-time variations of fundamental constants, which can be detected through atomic spectroscopy. In this study, we examine the effects of a varying nuclear mass $m_{N}$ and nuclear radius $r_{N}$ on two transition ratios: the comparison of the two-photon transition in atomic hydrogen with the hyperfine transition in $^{133}$Cs based clocks, and the ratio of optical clock frequencies in in Al$^{+}$ and Hg$^{+}$. The sensitivity of these frequency ratios to changes in $m_{N}$ and $r_{N}$ enables us to derive new limits on the variations of the proton mass, quark mass, and the QCD parameter $θ$. Additionally, we consider the scalar field generated by the Yukawa-type interaction of feebly interacting hypothetical scalar particles with Standard Model particles in the presence of massive bodies such as the Sun and Moon. Using the data from the Al$^{+}$/Hg$^{+}$, Yb$^{+}$/Cs and Yb$^{+}$(E2)/Yb$^{+}$(E3) transition frequency ratios, we place constraints on the interaction of the scalar field with photons, nucleons, and electrons for a range of scalar particle masses. We also investigate limits on the Einstein Equivalence Principle (EEP) violating term ($c_{00}$) in the Standard Model Extension (SME) Lagrangian and the dependence of fundamental constants on gravity.

hep-ph↗

arXiv2024

High-accuracy optical clocks with sensitivity to the fine-structure constant variation based on Sm$ ^{10+} $

We identify two metastable excited states in Sm$ ^{10+} $ highly charged ion as candidates for high accuracy optical clocks. Several atomic properties relevant to optical clock development are calculated using relativistic many-body methods. This includes energy levels, transition amplitudes, lifetimes, scalar polarizabilities, black body radiation shift, and the sensitivity to the fine structure constant variation. We found that the clock transitions are not sensitive to perturbation, e.g., relative black body radiation shifts are $\sim 10^{-19}$. The enhancement factor for the $α$ variation is $\sim$ 0.8 for one clock transition and $\sim$ 16 for another.

hep-ph↗

arXiv2024

Migdal-type effect in the dark matter absorption process

We propose a new mechanism of absorption of dark matter particles in atoms which resembles the Migdal effect of inelastic dark matter scattering. In this process, atom may be ionized upon absorption of a scalar particle through the scalar-nucleon Yukawa-type interaction. The crucial difference from the inelastic dark matter scattering on atoms is that the total energy of the particle, including its rest mass $mc^2$-term, is transferred to the electron. As a result, the emitted electron kinetic energy is about six orders in magnitude bigger than that in the dark matter scattering process. This absorption process allows one to probe dark matter particles with a relatively small mass, in the range from 1 to 100 keV, that cannot be detected in the scattering process. It is also possible to detect hypothetical scalar particles emitted from the Sun. We calculate absorption cross sections of this process in Na, Si, Ar, Ge, I, Xe, and Tl target atoms and extract limits on the scalar-nucleon interaction constant from null results of XENONnT experiment.

hep-ph↗

arXiv2024

Highly charged ions of heavy actinides as sensitive probes for time variation of the fine structure constant

Highly charged ions of heavy actinides from uranium to einsteinium are studied theoretically to find optical transitions sensitive to the variation of the fine structure constant. A number of promising transitions have been found in ions with ionisation degree $\sim$~10. All these transitions correspond in single-electron approximation to the $6p$ - $5f$ transitions. Many of the transitions are between ground and excited metastable states of the ions which means that they can probably be used as optical clock transitions. Some of the ions have more than one clock transition with different sensitivity to the variation of the fine structure constant $α$. The most promising systems include the Np$^{10+}$, Np$^{9+}$, Pu$^{11+}$, Pu$^{10+}$, Pu$^{9+}$, Pu$^{8+}$, Bk$^{15+}$, Cm$^{12+}$, and Es$^{15+}$ ions.

physics.atom-ph↗

arXiv2023

Cm$^{15+}$ and Bk$^{16+}$ ion clocks with enhanced sensitivity to new physics

We perform calculations of electronic structure of Cm$^{15+}$ and Bk$^{16+}$ ions and demonstrate that they have transitions which combine the features of atomic optical clocks with the enhanced sensitivity to the variations of the fine structure constant $α$. The high sensitivity is due to large nuclear charge $Z$, high ionisation degree $Z_i$ and the effect of {\em level crossing}, which enables optical transitions between states of different configurations. These are the $6p_{1/2}-5f_{5/2} $ and $6p_{1/2}-5f_{7/2} $ transitions in the single valence electron approximation. Variation of $α$ may be due to the interaction with scalar and pseudoscalar (axion) dark matter fields. Therefore, Cm$^{15+}$ and Bk$^{16+}$ clocks are promising candidates to search for these fields.

physics.atom-ph↗

arXiv2023

The Os$^{16+}$ and Ir$^{17+}$ ions as candidates for accurate optical clock sensitive to physics beyond standard model

We perform detailed calculations of the electronic structure of the Os$^{16+}$ ion and demonstrate that it has several metastable states which can be used for very accurate optical clocks. The clocks are highly sensitive to manifestations of the physics beyond standard model, such as time variation of the fine structure constant $α$, interaction with scalar and pseudoscalar (axion) dark matter fields, local Lorentz invariance and local position invariance violations, and interaction of atomic electrons with nucleus mediated by new boson. The latter can be studied by analysing King plot for isotope shifts and its possible non-linearities since Os has 5 stable isotopes with zero nuclear spin. Similar calculations for the Ir$^{17+}$ ion spectra demonstrate very good agreement between theory and experiment. This helps to validate the method of the calculations and demonstrate that both ions are excellent candidates for the search of new physics.

physics.atom-ph↗

arXiv2023

Shift of nuclear clock transition frequency in $^{229}$Th ions due to hyperfine interaction

We calculate hyperfine structure of $^{229}$Th and its ions (Th~IV, Th~III, Th~II, Th~I) to reveal the dependence of the nuclear clock frequency on the hyperfine interaction (hfi). We calculate first and second-order hfi shifts and demonstrate that due to the differences in the hyperfine structure for different ions and for the ground and isomeric nuclear states, the nuclear frequencies in Th~IV, Th~III, Th~II and Th~I are also different. The first-order shift of frequency is large for a particular hyperfine component, but it vanishes after averaging over all hyperfine states. The second-order shift is small but it does not vanish after averaging. It is three to six orders of magnitude smaller than the shift of the nuclear frequencies due to the Coulomb electron-nucleus interaction considered in our previous work (V. A. Dzuba and V. V. Flambaum, arXiv:2309.11176 (2023)). However, it is six to eight orders of magnitude larger than the projected accuracy of the nuclear clock ($10^{-19}$).

physics.atom-ph↗

arXiv2023

Effects of electrons on nuclear clock transition frequency in $^{229}$Th ions

We perform calculations of the energy shift of the nuclear clock transition frequency $^{229}$Th as a function of the number of electrons in Th ion. We demonstrate that the dependence of the nuclear frequency on electron configuration is significant. E.g., removing one electron from the atom leads to relative shift of the nuclear frequency $\sim 10^{-7}$, which is twelve orders of magnitude larger than expected relative uncertainty of the nuclear clock transition frequency ($\sim 10^{-19}$). This leads to difference of the nuclear clock frequencies in Th~IV, Th~III, Th~II and Th~I. The relative change of the nuclear frequency between neutral Th and its bare nucleus is 1\%. We also calculate the field shift constants for isotopic and isomeric shifts of atomic electron transitions in Th ions.

physics.atom-ph↗