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V. V. Flambaum

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

At least 361 records · Page 20Linked to original sources
arXiv2003

Scattering of scalar particles by a black hole

The absorption cross section for scalar particle impact on a Schwarzschild black hole is found. The process is dominated by two physical phenomena. One of them is the well-known greybody factor that arises from the energy-dependent potential barrier outside the horizon that filters the incoming and outgoing waves. The other is related to the reflection of particles on the horizon (Kuchiev 2003). This latter effect strongly diminishes the cross section for low energies, forcing it to vanish in the infrared limit. It is argued that this is a general property, the absorption cross section vanishes in the infrared limit for scattering of particles of arbitrary spin.

gr-qc↗
arXiv2003

Constraining Variations in the Fine-structure Constant, Quark Masses and the Strong Interaction

We present evidence for variations in the fine-structure constant from Keck/HIRES spectra of 143 quasar absorption systems over the redshift range 0.2 < z_abs < 4.2. This includes 15 new systems, mostly at high-z (z_abs > 1.8). Our most robust estimate is a weighted mean da/a=(-0.57 +/- 0.11)x10^{-5}. We respond to recent criticisms of the many-multiplet method used to extract these constraints. The most important potential systematic error at low-z is the possibility of very different Mg heavy isotope abundances in the absorption clouds and laboratory: {\it higher} abundances of {25,26}Mg in the absorbers may explain the low-z results. Approximately equal mixes of {24}Mg and {25,26}Mg are required. Observations of Galactic stars generally show {\it lower} {25,26}Mg isotope fractions at the low metallicities typifying the absorbers. Higher values can be achieved with an enhanced population of intermediate mass stars at high redshift, a possibility at odds with observed absorption system element abundances. At present, all observational evidence is consistent with the varying-alpha results. Another promising method to search for variation of fundamental constants involves comparing different atomic clocks. Here we calculate the dependence of nuclear magnetic moments on quark masses and obtain limits on the variation of alpha and m_q/Lambda_QCD from recent atomic clock experiments with hyperfine transitions in H, Rb, Cs, Hg+ and an optical transition in Hg+.

astro-ph↗
arXiv2003

Cosmological variation of deuteron binding energy, strong interaction and quark masses from big bang nucleosynthesis

We use Big Bang Nucleosynthesis calculations and light element abundance data to constrain the relative variation of the deuteron binding energy since the universe was a few minutes old, $δQ = Q(BBN)-Q(present)$. Two approaches are used, first treating the baryon to photon ratio, $η$, as a free parameter, but with the additional freedom of varying $δQ$, and second using the WMAP value of $η$ and solving only for $δQ$. Including varying $Q$ yields a better fit to the observational data than imposing the present day value, rectifying the discrepancy between the $^4He$ abundance and the deuterium and $^7Li$ abundances, {\it and} yields good agreement with the independently determined $η_{WMAP}$. The minimal deviation consistent with the data is significant at about the 4-$σ$ level; $δQ/Q= -0.019 \pm 0.005$. If the primordial $^4$He abundance lies towards the low end of values in the literature, this deviation is even larger and more statistically significant. Taking the light element abundance data at face-value, our result may be interpreted as variation of the dimensionless ratio $X=m_s/Λ_{QCD}$ of the strange quark mass and strong scale: $δX/X=(1.1 \pm 0.3) \times 10^{-3}$. These results provide a strong motivation for a more thorough exploration of the potential systematic errors in the light element abundance data.

astro-ph↗
arXiv2003

Limits on temporal variation of fine structure constant, quark masses and strong interaction from atomic clock experiments

We perform calculations of the dependence of nuclear magnetic moments on quark masses and obtain limits on the variation of the ratio of quark mass and strong interaction scale (m_q/Lambda_{QCD}) from recent atomic clock experiments with hyperfine transitions in H, Rb, Cs, Yb+, Hg+ and optical transition in Hg+. Experiments with Cd+, deuterium/hydrogen, molecule SF_6, Zeeman transitions in He_3/Xe are also discussed.

physics.atom-ph↗
arXiv2003

Violations of fundamental symmetries in atoms and tests of unification theories of elementary particles

High-precision measurements of violations of fundamental symmetries in atoms are a very effective means of testing the standard model of elementary particles and searching for new physics beyond it. Such studies complement measurements at high energies. We review the recent progress in atomic parity nonconservation and atomic electric dipole moments (time reversal symmetry violation), with a particular focus on the atomic theory required to interpret the measurements.

physics.atom-ph↗
arXiv2003

Further evidence for a variable fine-structure constant from Keck/HIRES QSO absorption spectra

[Abridged] We previously presented evidence for a varying fine-structure constant, alpha, in two independent samples of Keck/HIRES QSO spectra. Here we present a detailed many-multiplet analysis of a third Keck/HIRES sample containing 78 absorption systems. We also re-analyse the previous samples, providing a total of 128 absorption systems over the redshift range 0.2<z_abs<3.7. All three samples separately yield consistent, significant values of da/a. The analyses of low- and high-z systems rely on different ions/transitions with very different dependencies on alpha, yet they also give consistent results. We identify additional random errors in 22 high-z systems characterized by transitions with a large dynamic range in apparent optical depth. Increasing the statistical errors on da/a for these systems gives our fiducial result, a weighted mean da/a=(-0.543+/-0.116)x10^-5, representing 4.7-sigma evidence for a smaller weighted mean alpha in the absorption clouds. Assuming that da/a=0 at z_abs=0, the data marginally prefer a linear increase in alpha with time: dota/a=(6.40+/-1.35)x10^-16 yr^-1. The two-point correlation function for alpha is consistent with zero over 0.2-13 Gpc comoving scales and the angular distribution of da/a shows no significant dipolar anisotropy. We therefore have no evidence for spatial variations in da/a. We extend our previous searches for possible systematic errors, identifying atmospheric dispersion and isotopic structure effects as potentially the most significant. However, overall, known systematic errors do not explain the results. Future many-multiplet analyses of QSO spectra from different telescopes and spectrographs will provide a now crucial check on our Keck/HIRES results.

astro-ph↗
arXiv2003

Isotope shift calculations for atoms with one valence electron

This work presents a method for the ab initio calculation of isotope shift in atoms and ions with one valence electron above closed shells. As a zero approximation we use relativistic Hartree-Fock and then calculate correlation corrections. The main motivation for developing the method comes from the need to analyse whether different isotope abundances in early universe can contribute to the observed anomalies in quasar absorption spectra. The current best explanation for these anomalies is the assumption that the fine structure constant, alpha, was smaller at early epoch. We test the isotope shift method by comparing the calculated and experimental isotope shift for the alkali and alkali-like atoms Na, MgII, K, CaII and BaII. The agreement is found to be good. We then calculate the isotope shift for some astronomically relevant transitions in SiII and SiIV, MgII, ZnII and GeII.

physics.atom-ph↗
arXiv2003

Relativistic effects in Sr, Dy, YbII and YbIII and search for variation of the fine structure constant

A possibility for fundamental constants to vary in time is suggested by theories unifying gravity with other interactions. In this article we examine proposals to use optical transitions of Sr, Dy, YbII and YbIII for the search of the time variation of the fine structure constant $α$. Frequencies of atomic transitions are calculated using relativistic Hartree-Fock method and configuration interaction technique. The effect of variation of $α$ on the frequencies is studied by varying $α$ in computer codes. Accuracy of measurements needed to improve current best limit on the time variation of $α$ is discussed.

physics.atom-ph↗
arXiv2003

Radiative corrections to parity-non-conservation in atoms

Recent progress in calculations of QED radiative corrections to parity nonconservation in atoms is reviewed. The QED vacuum polarization, the self-energy corrections and the vertex corrections are shown to be described very reliably by different methods used by different groups. All new calculations have recently converged to very close final values. Each separate radiative correction is very large, above 1 % for heavy atoms, but having different signs they partly compensate each other. Our results for the radiative corrections for all atoms are presented. The corrections are -0.54 % for 133 Cs, and -0.70% for 205 Tl, 208 Pb, and 209 Bi. The result for 133 Cs reconciles the most accurate atomic experimental data for the 6s-7s PNC amplitude in 133 Cs of Wood et al with the standard model.

hep-ph↗
arXiv2003

Dependence of hadronic properties on Quark Masses and Constraints on their Cosmological Variation

We follow our previous paper on possible cosmological variation of weak scale (quark masses) and strong scale, inspired by data on cosmological variation of the electromagnetic fine structure constant from distant quasar (QSO) absorption spectra. In this work we identify the {\em strange quark mass} $m_s$ as the most important quantity, and the {\em sigma meson mass} as the ingredient of the nuclear forces most sensitive to it. As a result, we claim significantly stronger limits on ratio of weak/strong scale ($W=m_s/Λ_{QCD}$) variation following from our previous discussion of primordial Big-Bang Nucleosynthesis ($|δW/W|<0.006$) and Oklo natural nuclear reactor ($|δW/W|<1.2 \cdot 10^{-10}$; there is also a non-zero solution $δW/W=(-0.56 \pm 0.05) \cdot 10^{-9}$) .

hep-ph↗
arXiv2002

Enhancement of nuclear Schiff moments and time reversal violation in atoms due to soft nuclear octupole vibrations

Parity and time invariance violating (${\cal P},{\cal T}$-odd) nuclear forces produce ${\cal P},{\cal T}$-odd nuclear moments, for example, the nuclear Schiff moment. In turn, this moment can induce electric dipole moments (EDMs) in atoms. We estimate the contribution to the Schiff moment from the soft collective octupole vibrations existing in many heavy nuclei. Two possible mechanisms are considered, mixing of the ground state of an odd-$A$ nucleus with the octupole phonon state, and ${\cal P},{\cal T}$-odd admixture to the single-particle wave function of the valence nucleon. We found practically the same contribution to the Schiff moment as that of the static octupole deformation calculated earlier. This confirms a suggestion that the soft octupole vibrations can replace the (controversial) static octupoles in development of the collective Schiff moments. The values of atomic EDM predicted for $^{223,225}$Ra and $^{223}$Rn are enhanced by factors up to $10^{3}$ compared to experimentally studied spherical nuclei $^{199}$Hg and $^{129}$Xe.

nucl-th↗
arXiv2002

Does the fine structure constant vary? A third quasar absorption sample consistent with varying alpha

We report preliminary results from a third sample of quasar absorption line spectra from the Keck telescope which has been studied to search for any possible variation of the fine structure constant, alpha. This third sample, which is larger than the sum of the two previously published samples, shows the same effect, and also gives, as do the previous two samples, a significant result. The combined sample yields a highly significant effect, da/a = (alpha_z - alpha_0)/alpha_0 = -0.57 +/- 0.10 x 10^{-5}, averaged over the redshift range 0.2 < z < 3.7. We include a brief discussion of small-scale kinematic structure in quasar absorbing clouds. However, kinematics are unlikely to impact significantly on the averaged non-zero da/a above, and we have so far been unable to identify any systematic effect which can explain it. New measurements of quasar spectra obtained using independent instrumentation and telescopes are required to properly check the Keck results.

astro-ph↗
arXiv2002

Does the fine structure constant vary? A detailed investigation into systematic effects

We have previously presented 5.7-sigma evidence for a smaller alpha at redshifts 0.2 < z_abs < 3.7 from a sample of 128 Keck/HIRES quasar absorption systems: da/a = (-0.57 +/- 0.10) x 10^{-5}. A non-zero da/a manifests itself as a distinct pattern of shifts in the measured absorption line wavelengths. The statistical error is now small: we do detect small line shifts in the HIRES data. Whether these shifts are due to systematic errors or due to real variation in alpha is now the central question. Here we summarize the two potentially most important systematic effects: atmospheric dispersion and isotopic abundance evolution. Previously, these have been difficult to quantify/model but here we find that neither of them can explain our results. Furthermore, the HIRES spectra themselves contain no evidence for these effects. Independent measurements of da/a with a different telescope and spectrograph are now crucial if we are to rule out or confirm the present evidence for a variable alpha.

astro-ph↗
arXiv2002

Time evolution of the fine structure constant

We present a short review of the current quasar (QSO) absorption line constraints on possible variation of the fine structure constant, alpha = e^2/(hbar*c). Particular attention is paid to recent optical Keck/HIRES spectra of 49 absorption systems which indicate a smaller alpha in the past (Murphy et al. 2001, Webb et al. 2001). Here we present new preliminary results from 128 absorption systems: da/a = (-0.57 +/- 0.10) x 10^{-5} over the redshift range 0.2 < z < 3.7, in agreement with the previous results. Known potential systematic errors cannot explain these results. We compare them with strong `local' constraints and discuss other (radio and millimetre-wave) QSO absorption line constraints on variations in alpha^2 * g_p and alpha^2 * g_p * m_e/m_p (g_p is the proton g-factor and m_e/m_p is the electron/proton mass ratio). Finally, we discuss future efforts to rule out or confirm the current 5.7 sigma optical detection.

astro-ph↗
arXiv2002

Comment on "Black holes constrain varying constants"

A recent paper [DDL] claims that the increase of the proton electric charge e leads to a (forbidden) decrease of black hole entropy, therefore, possible evidence for variation of $α=e^2/\hbar c$ [alpha] must be interpreted as a decrease of the speed of light. We argue that purely theoretical consideration of black holes possibly cannot give any model-independent limitations on variation of fundamental constants.

astro-ph↗