Orientation relationship between α-Fe precipitate and α-Al2O3 matrix in iron-implanted sapphire

Fe ions were implanted into α-Al₂O₃ single crystals (sapphire) at room temperature and annealed in a reducing atmosphere. The orientation relationships (ORs) between α-Fe particles and sapphire matrix were investigated using transmission electron microscopy (TEM). All the α-Fe particles have the orientation relationship (OR) of (1 1 1)_α-Fe || (0 0 0 1)_sapphire and ${[1\overline{1}0]}_{\alpha \text{-Fe}}\left|\right|{[11\overline{2}0]}_{\text{sapphire}}$ with sapphire. This OR is predicted precisely by the coincidence of reciprocal lattice points (CRLP) method. The other OR of (1 1 0)_α-Fe || (0 0 0 1)_sapphire and ${[111]}_{\alpha \text{-Fe}}\left|\right|{[5\overline{1}\overline{4}0]}_{\text{sapphire}}$ reported before is confirmed by the same method to be one of the secondary preferred orientation relationships in the α-Fe/sapphire system.     

Temperature effects in five-dimensional Kaluza-Klein theory

We examine the combined effectsof thermal and quantum-mechanical fluctuations in a Kaluza-Klein universe with a single compact spatial dimension of length ${\overline{L}}_5$. From the one-loop effective potential for ${\overline{L}}_5$ two types of instability are evident. If initially ${\overline{L}}_5$ is less than a temperature-dependent critical length, ${\overline{L}}_5$ will shrink at least down to a length comparable to the Planck length. This instability has been noted by Appelquist and Chodos in the zero-temperature limit. If, on the other hand, ${\overline{L}}_5$ starts out larger than the critical length, it will tend to increase. This result suggests that temperature effects may play an important role in Kaluza-Klein cosmological models.     

A fresh look into m¯c,b(m¯c,b) and precise fD(s),B(s) from heavy–light QCD spectral sum rules

Using recent values of the QCD (non-)perturbative parameters given in Table 1 and an estimate of the N3LO QCD perturbative contributions based on the geometric growth of the PT series, we re-use QCD spectral sum rules (QSSR) known to N2LO PT series and including all dimension-six NP condensate contributions in the full QCD theory, for improving the existing estimates of ${\overline{m}}_{c,b}$ and $f_{D_{(s)},B_{(s)}}$ from the open charm and beauty systems. We especially study the effects of the subtraction point on “different QSSR data” and use (for the first time) the Renormalization Group Invariant (RGI) scale-independent quark masses in the analysis. The estimates [rigourous model-independent upper bounds within the SVZ framework] reported in Table 8: $f_D/f_{\pi }=1.56(5)$ $[?1.68(1)]$, $f_B/f_{\pi }=1.58(5)$ $[?1.80(3)]$ and $f_{D_s}/f_K=1.58(4)$ $[?1.63(1)]$, $f_{B_s}/f_K=1.50(3)$ $[?1.61(3.5)]$, which improve previous QSSR estimates, are in perfect agreement (in values and precisions) with some of the experimental data on $f_{D,D_s}$ and on recent lattice simulations within dynamical quarks. These remarkable agreements confirm both the success of the QSSR semi-approximate approach based on the OPE in terms of the quark and gluon condensates and of the Minimal Duality Ansatz (MDA) for parametrizing the hadronic spectral function which we have tested from the complete data of the $J/\psi$ and ? systems. The values of the running quark masses ${\overline{m}}_c(m_c)=1286(66)\text{MeV}$ and ${\overline{m}}_b(m_b)=4236(69)\text{MeV}$ from $M_{D,B}$ are in good agreement though less accurate than the ones from recent $J/\psi$ and ? sum rules.     

Brouillage thermique d'un gaz cohérent de fermions

It is generally assumed that a condensate of paired fermions at equilibrium is characterized by a macroscopic wavefunction with a well-defined, immutable phase. In reality, all systems have a finite size and are prepared at non-zero temperature; the condensate has then a finite coherence time, even when the system is isolated in its evolution and the particle number N is fixed. The loss of phase memory is due to interactions of the condensate with the excited modes that constitute a dephasing environment. This fundamental effect, crucial for applications using the condensate of pairs' macroscopic coherence, was scarcely studied. We link the coherence time to the condensate phase dynamics, and we show with a microscopic theory that the time derivative of the condensate phase operator ${\hat{\theta }}_0$ is proportional to a chemical potential operator that we construct including both the pair-breaking and pair-motion excitation branches. In a single realization of energy E, ${\hat{\theta }}_0$ evolves at long times as $-2{\mu }_{\mathrm{mc}}(E)t/ħ$, where ${\mu }_{\mathrm{mc}}(E)$ is the microcanonical chemical potential; energy fluctuations from one realization to the other then lead to a ballistic spreading of the phase and to a Gaussian decay of the temporal coherence function with a characteristic time $\propto N^{1/2}$. In the absence of energy fluctuations, the coherence time scales as N due to the diffusive motion of ${\hat{\theta }}_0$. We propose a method to measure the coherence time with ultracold atoms, which we predict to be tens of milliseconds for the canonical ensemble unitary Fermi gas.     

Investigation of structural and electronic properties of β- HgS: Molecular dynamics simulations

The pressure induced phase transition of β-HgS is studied using an ab initio molecular dynamics simulation. The structural phase transformation from the zinc-blende structure to the NaCl-type structure (space group $Fm\overline{3}m$) and from this structure to CsCl-type structure ($Pm\overline{3}m$) with the application of hydrostatic pressure is predicted. Additionally, the electronic properties of HgS and various physical properties such as the lattice constants, the bulk modulus and the pressure derivative of the bulk modulus are revealed. Furthermore, these phase transitions are obtained using the total energy and enthalpy calculations. According to these calculations these transformations are occurring at about 20?GPa and 28?GPa for $F\overline{4}3m$ →$Fm\overline{3}m$ and $Fm\overline{3}m$ →$Pm\overline{3}m$, respectively.