Certification of programs with computational effects

In purely functional programming languages imperative features, more generally computational effects are prohibited. However, non-functional lan- guages do involve effects. The theory of decorated logic provides a rigorous for- malism (with a refinement in operation signatures) for proving program properties with respect to computational effects. The aim of this thesis is to first develop Coq libraries and tools for verifying program properties in decorated settings as- sociated with several effects: states, local state, exceptions, non-termination, etc. Then, these tools will be combined to deal with several effects

Screened hybrid functional applied to 3d^0-->3d^8 transition-metal perovskites LaMO3 (M=Sc-Cu): influence of the exchange mixing parameter on the structural, electronic and magnetic properties

We assess the performance of the Heyd-Scuseria-Ernzerhof (HSE) screened hybrid density functional scheme applied to the perovskite family LaMO3 (M=Sc-Cu) and discuss the role of the mixing parameter alpha (which determines the fraction of exact Hartree-Fock exchange included in the density functional theory (DFT) exchange-correlation functional) on the structural, electronic, and magnetic properties. The physical complexity of this class of compounds, manifested by the largely varying electronic characters (band/Mott-Hubbard/charge-transfer insulators and metals), magnetic orderings, structural distortions (cooperative Jahn-Teller like instabilities), as well as by the strong competition between localization/delocalization effects associated with the gradual filling of the t_2g and e_g orbitals, symbolize a critical and challenging case for theory. Our results indicates that HSE is able to provide a consistent picture of the complex physical scenario encountered across the LaMO3 series and significantly improve the standard DFT description. The only exceptions are the correlated paramagnetic metals LaNiO3 and LaCuO3, which are found to be treated better within DFT. By fitting the ground state properties with respect to alpha we have constructed a set of 'optimum' values of alpha from LaScO3 to LaCuO3: it is found that the 'optimum' mixing parameter decreases with increasing filling of the d manifold (LaScO3: 0.25; LaTiO3 & LaVO3: 0.10-0.15; LaCrO3, LaMnO3, and LaFeO3: 0.15; LaCoO3: 0.05; LaNiO3 & LaCuO3: 0). This trend can be nicely correlated with the modulation of the screening and dielectric properties across the LaMO3 series, thus providing a physical justification to the empirical fitting procedure.Comment: 32 pages, 29 figure

Harmony, Head Proximity, and the Near Parallels between Nominal and Clausal Linkers

This paper puts forward a notion of harmonic word order that leads to a new generalisation over the presence or absence of disharmony: specific functional heads must cross-linguistically obey this notion of harmony absolutely, while for other categories the presence of harmony is simply a tendency. The difference between the two classes is defined by semantics. This approach allows us both to draw certain parallels between restrictions on word order in nominals and in clauses, and furthermore to explain why other expected parallels should fail to be realised completely, specifically as regards differences in the distribution of relative clauses in the NP and complement clauses in the sentence. Syntactically independent relative clause markers and subordinating complementisers share a striking restriction as regards ordering: relative clause markers are always initial in postnominal relative clauses, and final in prenominal relative clauses (Andrews 1975; Downing 1978; Lehmann 1984; Keenan 1985; De Vries 2002, 2005); similarly, initial subordinating Cs only appear in postverbal complement clauses, while final subordinating Cs are only possible where the complement clause is preverbal (Bayer 1996, 1997, 1999; Kayne 2000). In this paper, I provide new evidence from eighty genetically and geographically diverse languages of a third category sharing precisely the same restriction: linkers in the complex NP. These are syntactically independent, semantically vacuous heads, serving to mark the presence of a relationship between a noun and any kind of phrasal dependent (Rubin 2002; Den Dikken and Singhapreecha 2004; Philip 2009). The class of linkers in the NP therefore includes the ezafe in Indo-Iranian, the associative marker -a in Bantu, as well as purely functional adpositions such as of in English. Like relative clause markers and subordinating Cs, the linker always intervenes linearly between the superordinate head (the noun) and the subordinate dependent. Crucially, relative clause markers, subordinating Cs, and linkers in the NP form a natural class: they are syntactically independent, semantically vacuous words serving purely to mark the presence of a relationship between head and dependent. Any member of this class is a ‘linker’. I propose a theory of disharmony whereby linearisation rules targeting heads with specified semantics can require such heads to appear in a prominent position, either initial or final, irrespective of the general headedness of the language. Linkers, being semantically vacuous, are of course impervious to such rules; they will therefore always conform to the harmonic, or optimal, word order. I propose a theory of harmony whereby the optimal word order is determined by the interaction of three independently motivated harmonic word order constraints: Head Proximity (adapted from Rijkhoff 1984, 1986, cf. Head-Final Filter, Williams 1982), the preference for uniformity in headedness (initial or final), and the preference for clausal dependents to appear in final position (Dryer 1980, 1992). Where the three constraints compete, it is always Head Proximity that takes precedence. I show that the distribution of all three types of linker is fully captured by this proposal. Moreover, this theory of ordering also accounts for another well observed near parallel between clauses and nominals, as well as its exceptions. This concerns a left-right asymmetry in the distribution of clausal dependents: while in OV languages complement clauses appear with near equal frequency in both preverbal and postverbal position, in VO languages they are found uniquely in postverbal position (Dryer 1980; Hawkins 1994; Dryer 2009); similarly, in OV languages relative clauses are distributed relatively evenly between prenominal and postnominal position, whereas in VO languages they are almost always postnominal, with very few exceptions (Mallinson & Blake 1981; Hawkins 1983, 1990; Lehmann 1984; Keenan 1985; Dryer 1992, 2007, 2008; De Vries 2005). The theory predicts these exceptions to be permitted only in languages that are rigidly N-final. Hawkins’ (1983) Noun Modifier Hierarchy suggests that this prediction is borne out; apparent exceptions (cf. Dryer 2008) are found underlyingly to be N-final

Assessment of First-Principles and Semiempirical Methodologies for Absorption and Emission Energies of Ce3+^{3+}-Doped Luminescent Materials

In search of a reliable methodology for the prediction of light absorption and emission of Ce$^{3+}$-doped luminescent materials, 13 representative materials are studied with first-principles and semiempirical approaches. In the first-principles approach, that combines constrained density-functional theory and $\Delta$SCF, the atomic positions are obtained for both ground and excited states of the Ce$^{3+}$ ion. The structural information is fed into Dorenbos' semiempirical model. Absorption and emission energies are calculated with both methods and compared with experiment. The first-principles approach matches experiment within 0.3 eV, with two exceptions at 0.5 eV. In contrast, the semiempirical approach does not perform as well (usually more than 0.5 eV error). The general applicability of the present first-principles scheme, with an encouraging predictive power, opens a novel avenue for crystal site engineering and high-throughput search for new phosphors and scintillators.Comment: 12 pages, 3 figure

On the canonical degrees of curves in varieties of general type

A widely believed conjecture predicts that curves of bounded geometric genus lying on a variety of general type form a bounded family. One may even ask whether the canonical degree of a curve $C$ in a variety of general type is bounded from above by some expression $a\chi(C)+b$, where $a$ and $b$ are positive constants, with the possible exceptions corresponding to curves lying in a strict closed subset (depending on $a$ and $b$). A theorem of Miyaoka proves this for smooth curves in minimal surfaces, with $a>3/2$. A conjecture of Vojta claims in essence that any constant $a>1$ is possible provided one restricts oneself to curves of bounded gonality. We show by explicit examples coming from the theory of Shimura varieties that in general, the constant $a$ has to be at least equal to the dimension of the ambient variety. We also prove the desired inequality in the case of compact Shimura varieties.Comment: 10 pages, to appear in Geometric and Functional Analysi

On exceptional stress assignment in Latvian: the case of prefixes

This is an Accepted Manuscript of an article published by Taylor & Francis in Journal of Baltic Studies on 09.05.2018, available at: https://doi.org/10.1080/01629778.2018.1466817.In this article, we examine some previously understudied exceptions to the generalization that Latvian assigns stress to the left-most syllable in a prosodic word, specifically those that involve prefixation. We will show that these apparent exceptions in stress assignment follow from the internal structural properties of the word and are a result of attaching the prefix outside the domain where stress is assigned, which is up to the first functional head inside the hierarchy. Our treatment combines the syntactic structure of a neoconstructionist approach to word formation with an optimality theory formalization at the phonological level

Hydrogen Dissociation and Diffusion on Transition Metal(=Ti,Zr,V,Fe,Ru,Co,Rh,Ni,Pd,Cu,Ag)-doped Mg(0001) Surfaces

The kinetics of hydrogen absorption by magnesium bulk is affected by two main activated processes: the dissociation of the H$_2$ molecule and the diffusion of atomic H into the bulk. In order to have fast absorption kinetics both activated processed need to have a low barrier. Here we report a systematic ab-initio density functional theory investigation of H$_2$ dissociation and subsequent atomic H diffusion on TM(=Ti,V,Zr,Fe,Ru,Co,Rh,Ni,Pd,Cu,Ag)-doped Mg(0001) surfaces. The calculations show that doping the surface with TM's on the left of the periodic table eliminates the barrier for the dissociation of the molecule, but the H atoms bind very strongly to the TM, therefore hindering diffusion. Conversely, TM's on the right of the periodic table don't bind H, however, they do not reduce the barrier to dissociate H$_2$ significantly. Our results show that Fe, Ni and Rh, and to some extent Co and Pd, are all exceptions, combining low activation barriers for both processes, with Ni being the best possible choice.Comment: accepted in the International Journal of Hydrogen Energ

Rotating mixed 3^3He-4^4He nanodroplets

Mixed $^3$He-$^4$He droplets created by hydrodynamic instability of a cryogenic fluid-jet may acquire angular momentum during their passage through the nozzle of the experimental apparatus. These free-standing droplets cool down to very low temperatures undergoing isotopic segregation, developing a nearly pure $^3$He crust surrounding a very $^4$He-rich superfluid core. Here, the stability and appearance of rotating mixed helium droplets are investigated using Density Functional Theory for an isotopic composition that highlights, with some marked exceptions related to the existence of the superfluid inner core, the analogies with viscous rotating droplets.Comment: 6 pages, 4 figures (plus Supplemental Material). Revised version with corrections+missing figur

Stabilized Spin-Polarized Jellium Model and Odd-Even Alternations in Jellium Metal Clusters

In this paper, we have considered the mechanical stability of a jellium system in the presence of spin degrees of freedom and have generalized the stabilized jellium model, introduced by J. P. Perdew, H. Q. Tran, and E. D. Smith [Phys. Rev. B42, 11627 (1990)], to a spin-polarized case. By applying this generalization to metal clusters (Al, Ga, Li, Na, K, Cs), we gain additional insights about the odd-even alternations, seen in their ionization potentials. In this generalization, in addition to the electronic degrees of freedom, we allow the positive jellium background to expand as the clusters' polarization increases. In fact, our self-consistent calculations of the energetics of alkali metal clusters with spherical geometries, in the context of density functional theory and local spin density approximation, show that the energy of a cluster is minimized for a configuration with maximum spin compensation (MSC). That is, for clusters with even number of electrons, the energy minimization gives rise to complete compensation ($N_\uparrow=N_\downarrow$), and for clusters with odd number of electrons, only one electron remains uncompensated ($N_\uparrow-N_\downarrow=1$). It is this MSC-rule which gives rise to alternations in the ionization potentials. Aside from very few exceptions, the MSC-rule is also at work for other metal culsters (Al, Ga) of various sizes.Comment: 18 pages, Rev_Tex, 14 figures in PostScript, Extended and improved version of our recent article with the same titl