We present a new approach to describe statistics of the non-linear matter density field that exploits a degeneracy in the impact of different cosmological parameters on the linear matter power spectrum, $P_{rm L}(k)$, when expressed in Mpc units. We
classify all cosmological parameters into two groups, shape parameters, which determine the shape of $P_{rm L}(k)$, and evolution parameters, which only affect its amplitude at any given redshift. We show that the time evolution of $P_{rm L}(k)$ in models with identical shape parameters but different evolution parameters can be mapped from one to the other by relabelling the redshifts that correspond to the same values of $sigma_{12}(z)$, defined as the RMS linear variance in spheres of radius $12,{rm Mpc}$. We use N-body simulations to show that the same evolution mapping relation can be applied to the non-linear power spectrum, the halo mass function, or the full density field with high accuracy. The deviations from the exact degeneracy are the result of the different structure formation histories experienced by each model to reach the same value of $sigma_{12}(z)$. This relation can be used to drastically reduce the number of parameters required to describe the cosmology dependence of the power spectrum. We show how this degeneracy can be exploited to speed up the inference of parameter constraints from cosmological observations. We also present a new design of an emulator of the non-linear power spectrum whose predictions can be adapted to an arbitrary choice of evolution parameters and redshift.
Orbital memory is defined by two stable valencies that can be electrically switched and read-out. To explore the influence of an electric field on orbital memory, we studied the distance-dependent influence of an atomic Cu donor on the state favorabi
lity of an individual Co atom on black phosphorus. Using low temperature scanning tunneling microscopy/spectroscopy, we characterized the electronic properties of individual Cu donors, corroborating this behavior with ab initio calculations based on density functional theory. We studied the influence of an individual donor on the charging energy and stochastic behavior of an individual Co atom. We found a strong impact on the state favorability in the stochastic limit. These findings provide quantitative information about the influence of local electric fields on atomic orbital memory.
The structure and mobility of dislocations in the layered semiconductor InSe is studied within a multiscale approach based on generalized Peierls--Nabarro model with material-specific parametrization derived from first principles. The plasticity of I
nSe turns out to be attributed to peculiarities of the generalized stacking fault relief for the interlayer dislocation slips such as existence of the stacking fault with a very low energy and low energy barriers. Our results give a consistent microscopic explanation of recently observed [Science {bf 369}, 542 (2020)] exceptional plasticity of InSe.
First principles approaches have been successful in solving many-body Hamiltonians for real materials to an extent when correlations are weak or moderate. As the electronic correlations become stronger often embedding methods based on first principle
s approaches are used to better treat the correlations by solving a suitably chosen many-body Hamiltonian with a higher level theory. Such combined methods are often referred to as second principles approaches. At such level of the theory the self energy, i.e. the functional that embodies the stronger electronic correlations, is either a function of energy or momentum or both. The success of such theories is commonly measured by the quality of the self energy functional. However, self-consistency in the self-energy should, in principle, also change the real space charge distribution in a correlated material and be able to modify the electronic eigenfunctions, which is often undermined in second principles approaches. Here we study the impact of charge self-consistency within two example cases: TiSe$_{2}$, a three-dimensional charge-density-wave candidate material, and CrBr$_{3}$, a two-dimensional ferromagnet, and show how real space charge re-distribution due to correlation effects taken into account within a first principles Greens function based many-body perturbative approach is key in driving qualitative changes to the final electronic structure of these materials.
There are hints suggesting that properties of galaxy populations in dark matter haloes may depend on their large-scale environment. Recent works point out that very low-density environments influence halo occupation distribution (HOD), however there
is not a similar analysis focused on high-density environments. Here we use a simulated set of future virialized superstructures (FVS) to analyse the occupation of galaxies in haloes within these high globally dense regions. We use a publicly available simulated galaxy set constructed with a semi-analytical model to identify FVS in the simulation. Then, we computed the HOD within these superstructures for different absolute magnitude thresholds and make several analysis including the comparison to the global HOD results. We study the dependence on the results on properties of the FVS such as density and volume as well as consider the morphology of galaxies. We also analysed the properties of the stellar content of galaxies and the formation time of the haloes inside FVS. We find a significant increase in the HOD inside FVS. This result is present for all absolute magnitude thresholds explored. The effect is larger in the densest regions of FVS, but does not depend on the volume of the superstructure. We also find that the stellar-mass content of galaxies considerably differs inside the superstructures. Low mass haloes have their central and satellite galaxies with a higher stellar mass content (50%), and exhibit mean star ages (20%) older than average. For massive haloes in FVS we find that only the stellar mass of satellite galaxies varies considerably corresponding to a decrease of 50%. We find a significant statistical difference between the formation times of haloes in FVS and the average population. Haloes residing in superstructures formed earlier, a fact that leads to several changes in the HOD and their member galaxy properties.
Distance geometry problem belongs to a class of hard problems in classical computation that can be understood in terms of a set of inputs processed according to a given transformation, and for which the number of possible outcomes grows exponentially
with the number of inputs. It is conjectured that quantum computing schemes can solve problems belonging to this class in a time that grows only at a polynomial rate with the number of inputs. While quantum computers are still being developed, there are some classical optics computation approaches that can perform very well for specific tasks. Here, we present an optical computing approach for the distance geometry problem in one dimension and show that it is very promising in the classical computing regime.
The impact of leading collective electronic fluctuations on a free energy of a prototype 1D model for molecular systems is considered within the recently developed Fluctuating Local Field (FLF) approach. The FLF method is a non-perturbative extension
of a mean-field theory, where a self-consistent effective constant field is replaced by a fluctuating one. Integrating the fluctuating field out numerically exactly allows to account for collective electronic fluctuations mediated by this field without any assumptions on their magnitude, degree of nonlinearity, etc. Using a half-filled Hubbard ring as a benchmark system, we find that the FLF method noticeably improves a mean-field estimation for the free energy, in particular below the mean-field Neel temperature. We further demonstrate that the mean-field result can be even more improved introducing a multi-mode FLF scheme that additionally takes into account sub-leading fluctuations. Possible applications for the thermodynamics of real molecules are also discussed.
Dusty, neutral outflows and inflows are a common feature of nearby star-forming galaxies. We characterize these flows in eight galaxies -- mostly AGN -- selected for their widespread NaI D signatures from the Siding Spring Southern Seyfert Spectrosco
pic Snapshot Survey (S7). This survey employs deep, wide field-of-view integral field spectroscopy at moderate spectral resolution (R=7000 at NaI D). We significantly expand the sample of sightlines in external galaxies in which the spatially-resolved relationship has been studied between cool, neutral gas properties -- N(NaI), Weq(NaI D) -- and dust -- E(B-V) from both stars and gas. Our sample shows strong, significant correlations of total Weq with E(B-V)_stars and g-i colour within individual galaxies; correlations with E(B-V)_gas are present but weaker. Regressions yield slope variations from galaxy to galaxy and intrinsic scatter ~1 Angstrom. The sample occupies regions in the space of N(NaI) and Weq^abs vs. E(B-V)_gas that are consistent with extrapolations from other studies to higher colour excess [E(B-V)_gas ~ 1]. For perhaps the first time in external galaxies, we detect inverse P Cygni profiles in the NaI D line, presumably due to inflowing gas. Via Doppler shifted NaI D absorption and emission lines, we find ubiquitous flows that differ from stellar rotation by >100 km/s or have |v,abs - v,em| > 100 km/s. Inflows and outflows extend toward the edge of the detected stellar disk/FOV, together subtend 10-40% of the projected disk, and have similar mean N(NaI) and Weq(NaI D). Outflows are consistent with minor-axis or jet-driven flows, while inflows tend toward the projected major axis. The inflows may result from non-axisymmetric potentials, tidal motions, or halo infall.
Polaron tunneling is a prominent example of a problem characterized by different energy scales, for which the standard quantum Monte Carlo methods face a slowdown problem. We propose a new quantum-tunneling Monte Carlo (QTMC) method which is free fro
m this issue and can be used for a wide range of tunneling phenomena. We apply it to study an impurity interacting with a one-dimensional Bose-Einstein condensate and simultaneously trapped in an external double-well potential. Our scheme works for an arbitrary coupling between the particle and condensate and, at the same time, allows for an account of tunneling effects. We discover two distinct quasi-particle peaks associated, respectively, with the phonon-assisted tunneling and the self-trapping of the impurity, which are in a crossover regime for the system modeled. We observe and analyze changes in the weights and spectral positions of the peaks (or, equally, effective masses of the quasi-particles) when the coupling strength is increased. Possible experimental realizations using cold atoms are discussed.
We analyze the rest-optical emission-line spectra of $zsim2.3$ star-forming galaxies in the complete MOSFIRE Deep Evolution Field (MOSDEF) survey. In investigating the origin of the well-known offset between the sequences of high-redshift and local g
alaxies in the [O III]5008/H$beta$ vs. [N II]6585/H$alpha$ ([N II] BPT) diagram, we define two populations of $zsim2.3$ MOSDEF galaxies. These include the high population that is offset towards higher [O III]5008/H$beta$ and/or [N II]6585/H$alpha$ with respect to the local SDSS sequence and the low population that overlaps the SDSS sequence. These two groups are also segregated within the [O III]5008/H$beta$ vs. [S II]6718,6733/H$alpha$ and the [O III]4960,5008/[O II]3727,3730 (O$_{32}$) vs. ([O III]4960,5008+[O II]3727,3730)/H$beta$ (R$_{23}$) diagram, which suggests qualitatively that star-forming regions in the more offset galaxies are characterized by harder ionizing spectra at fixed nebular oxygen abundance. We also investigate many galaxy properties of the split sample and find that the high sample is on average smaller in size and less massive, but has higher specific star-formation rate and star-formation-rate surface density values and is slightly younger compared to the low population. From Cloudy+BPASS photoionization models, we estimate that the high population has a lower stellar metallicity (i.e., harder ionizing spectrum) but slightly higher nebular metallicity and higher ionization parameter compared to the low population. While the high population is more $alpha$-enhanced (i.e., higher $alpha$/Fe) than the low population, both samples are significantly more $alpha$-enhanced compared to local star-forming galaxies with similar rest-optical line ratios. These differences must be accounted for in all high-redshift star-forming galaxies -- not only those offset from local excitation sequences.
