Effects of turbulent dust grain motion to interstellar chemistry

Theoretical studies have revealed that dust grains are usually moving fast through the turbulent interstellar gas, which could have significant effects upon interstellar chemistry by modifying grain accretion. This effect is investigated in this work on the basis of numerical gas-grain chemical modeling. Major features of the grain motion effect in the typical environment of dark clouds (DC) can be summarised as follows: 1) decrease of gas-phase (both neutral and ionic) abundances and increase of surface abundances by up to 2-3 orders of magnitude; 2) shifts of the existing chemical jumps to earlier evolution ages for gas-phase species and to later ages for surface species by factors of about ten; 3) a few exceptional cases in which some species turn out to be insensitive to this effect and some other species can show opposite behaviors too. These effects usually begin to emerge from a typical DC model age of about 10^5 yr. The grain motion in a typical cold neutral medium (CNM) can help overcome the Coulomb repulsive barrier to enable effective accretion of cations onto positively charged grains. As a result, the grain motion greatly enhances the abundances of some gas-phase and surface species by factors up to 2-6 or more orders of magnitude in the CNM model. The grain motion effect in a typical molecular cloud (MC) is intermediate between that of the DC and CNM models, but with weaker strength. The grain motion is found to be important to consider in chemical simulations of typical interstellar medium.Comment: 20 pages, 10 figures and 2 table

Exact dynamics of dissipative electronic systems and quantum transport: Hierarchical equations of motion approach

A quantum dissipation theory is formulated in terms of hierarchically coupled equations of motion for an arbitrary electronic system coupled with grand canonical Fermion bath ensembles. The theoretical construction starts with the second--quantization influence functional in path integral formalism, in which the Fermion creation and annihilation operators are represented by Grassmann variables. Time--derivatives on influence functionals are then performed in a hierarchical manner, on the basis of calculus--on--path--integral algorithm. Both the multiple--frequency--dispersion and the non-Markovian reservoir parametrization schemes are considered for the desired hierarchy construction. The resulting formalism is in principle exact, applicable to interacting systems, with arbitrary time-dependent external fields. It renders an exact tool to evaluate various transient and stationary quantum transport properties of many-electron systems. At the second--tier truncation level the present theory recovers the real--time diagrammatic formalism developed by Sch\"{o}n and coworkers. For a single-particle system, the hierarchical formalism terminates at the second tier exactly, and the Landuer--B\"{u}ttiker's transport current expression is readily recovered.Comment: The new versio

Non-LTE analysis of copper abundances for the two distinct halo populations in the solar neighborhood

Two distinct halo populations were found in the solar neighborhood by a series of works. They can be clearly separated by [alpha\Fe] and several other elemental abundance ratios including [Cu/Fe]. Very recently, a non-local thermodynamic equilibrium (non-LTE) study revealed that relatively large departures exist between LTE and non-LTE results in copper abundance analysis. We aim to derive the copper abundances for the stars from the sample of Nissen et al (2010) with both LTE and non-LTE calculations. Based on our results, we study the non-LTE effects of copper and investigate whether the high-alpha population can still be distinguished from the low-alpha population in the non-LTE [Cu/Fe] results. Our differential abundance ratios are derived from the high-resolution spectra collected from VLT/UVES and NOT/FIES spectrographs. Applying the MAFAGS opacity sampling atmospheric models and spectrum synthesis method, we derive the non-LTE copper abundances based on the new atomic model with current atomic data obtained from both laboratory and theoretical calculations. The copper abundances determined from non-LTE calculations are increased by 0.01 to 0.2 dex depending on the stellar parameters compared with the LTE results. The non-LTE [Cu/Fe] trend is much flatter than the LTE one in the metallicity range -1.6<[Fe/H]<-0.8. Taking non-LTE effects into consideration, the high- and low-alpha stars still show distinguishable copper abundances, which appear even more clear in a diagram of non-LTE [Cu/Fe] versus [Fe/H]. The non-LTE effects are strong for copper, especially in metal-poor stars. Our results confirmed that there are two distinct halo populations in the solar neighborhood. The dichotomy in copper abundance is a peculiar feature of each population, suggesting that they formed in different environments and evolved obeying diverse scenarios.Comment: 9 pages, 7 figures, 2 table

Lower Bounds on the Ground State Entropy of the Potts Antiferromagnet on Slabs of the Simple Cubic Lattice

We calculate rigorous lower bounds for the ground state degeneracy per site, $W$, of the $q$-state Potts antiferromagnet on slabs of the simple cubic lattice that are infinite in two directions and finite in the third and that thus interpolate between the square (sq) and simple cubic (sc) lattices. We give a comparison with large-$q$ series expansions for the sq and sc lattices and also present numerical comparisons.Comment: 7 pages, late

Notes on highest weight modules of the elliptic algebra Aq,p(sl^2){\cal A}_{q,p}\left(\widehat{sl}_2\right)

We discuss a construction of highest weight modules for the recently defined elliptic algebra ${\cal A}_{q,p}(\widehat{sl}_2)$, and make several conjectures concerning them. The modules are generated by the action of the components of the operator $L$ on the highest weight vectors. We introduce the vertex operators $\Phi$ and $\Psi^*$ through their commutation relations with the $L$-operator. We present ordering rules for the $L$- and $\Phi$-operators and find an upper bound for the number of linearly independent vectors generated by them, which agrees with the known characters of $\widehat{sl}_2$-modules.Comment: Nonstandard macro package eliminate

Eksistensi Sistem Ekonomi Kapitalis di Indonesia

Sistem ekonomi kapitalis di Indonesia dilatarbelakangi oleh perseteruan politik antara negara-negara barat yang dikenal dengan sebutan blok barat dan negara-negara timur atau yang dikenal sebutan blok timur. Blok barat dalam mengembangkan perekonomian menggunakan konsep sistem ekonomi kapitalis sedangkan blok timur mengembangkan sistem ekonomi sosialis. Namun, dengan berbagai kekuatan propaganda yang dimiliki oleh negara-negara barat tentang penerapan sistem ekonomi kapitalis maka pandangan masyarakat dunia jauh lebih baik jika dibandingkan dengan sistem ekonomi sosialis. Walaupun Indonesia sebagai anggota negara Non Blok (tidak memihak salah satu) Blok,namun pemerintah kita dalam menerapkan sistem ekonomi masih menggunakan sistem ekonomi kapitalis. Hal ini dapat dilihat beberapa indikator yang tetap digunakan pemerintah, yaitu: pertama,dihapuskannya berbagai subsidi dari pemerintah secara bertahap. Berarti, harga dari barang-barang strategis yang selama ini penentuannya ditetapkan oleh pemerintah, selanjutnya secara berangsur diserahkan sepenuhnya pada mekanisme pasar. kedua,nilai kurs rupiah diambangkan secara bebas (floating rate). Sesuai dengan kesepakatan dalam LoI dengan pihak IMF, penentuan nilai kurs rupiah tidak boleh dipatok dengan kurs tetap (fix rate). Dengan kata lain, besarnya nilai kurs rupiah harus dikembalikan pada mekanisme pasar. ketiga, privatisasi BUMN. Salah satu ciri ekonomi yang liberal adalah semakin kecilnya peran pemerintah dalam bidang ekonomi, termasuk didalamnya adalah kepemilikan asset-asset produksi. Dengan dijualnya BUMN kepada pihak swasta, baik swasta nasional maupun asing, berarti perekonomian Indonesia semakin liberal. keempat, peran serta pemerintah Indonesia dalam kancah WTO dan perjanjian GATT. Dengan masuknya Indonesia dalam tata perdagangan dunia tersebut, semakin memperjelas komitmen Indonesia untuk masuk kubangan libelarisasi ekonomi dunia atau kapitalisme global