We demonstrate that a four-boson limit-cycle independent of the Efimov one appears in Hamiltonian systems at the unitary limit. The model interaction contains two-, three- and four-body short-range potentials, which disentangle the interwoven three- and four-boson cycles, for the universal trimer and tetramer energy levels, respectively. The limit-cycle associated with the correlation between the energies of two successive universal tetramer levels for fixed weakly bound trimer is found to be largely model independent. This is a universal manifestation of an independent four-boson scale associated with a cycle beyond the Efimov one.
We analyze two-particle binding factors for the case of \ch{H2} molecule with the help of our original Exact Diagonalization \textit{Ab Intio} (EDABI) approach. Explicitly, we redefine the many-particle covalency and ionicity factors as a function of interatomic distance. Insufficiency of those basic characteristics is stressed and the concept of \textit{atomicity} is introduced and corresponds to the Mott and Hubbard criteria concerning the localization in many-particle systems. This additional characteristic introduces atomic ingredient into the essentially molecular states and thus eliminates a spurious behavior of the standard covalency factor with the increasing interatomic distance, as well as provides a physical reinterpretation of the chemical bond's nature.
Alexey Potapov, Serge Krasnokutski, Cornelia Jäger
et al.
The solid-state reaction C + H$_2$O $\rightarrow$ H$_2$CO was studied experimentally following the codeposition of C atoms and H$_2$O molecules at low temperatures. In spite of the reaction barrier and absence of energetic triggering, the reaction proceeds fast on the experimental timescale pointing to its quantum tunneling mechanism. This route to formaldehyde shows a new "non-energetic" pathway to complex organic and prebiotic molecules in astrophysical environments. Energetic processing of the produced ice by UV irradiation leads mainly to the destruction of H$_2$CO and the formation of CO$_2$ challenging the role of energetic processing in the synthesis of complex organic molecules under astrophysically relevant conditions.
In this work, our statements are based on the progress of current research on superatomic clusters. Combining the new trend of materials and device manufacture at the atomic level, we analyzed the opportunities for the development based on the use of superatomic clusters as units of functional materials, and presented a foresight of this new branch of science with relevant studies on superatoms.
Rabi oscillations typify the inherent nonlinearity of optical excitations in quantum dots. Using an integral kernel formulation to solve the 3D Maxwell-Bloch equations in ensembles of up to $10^4$ quantum dots, we observe features in Rabi oscillations due to the interplay of nonlinearity, non-equilibrium excitation, and electromagnetic coupling between the dots. This approach allows us to observe the dynamics of each dot in the ensemble without resorting to spatial averages. Our simulations predict synchronized multiplets of dots that exchange energy, dots that dynamically couple to screen the effect of incident external radiation, localization of the polarization due to randomness and interactions, as well as wavelength-scale regions of enhanced and suppressed polarization.
Brian J. Harding, Jonathan J. Makela, John W. Meriwether
AbstractWe introduce a technique for estimating the regional thermospheric wind field from measurements made by a network of interferometers. Unlike previous work, this technique does not make assumptions about the functional form of the wind field and instead uses inverse theory to find the smoothest wind field that agrees with the measurements. This technique is general and applies to any network making radial velocity measurements. We show reconstructions of the thermospheric wind field over the eastern United States and over eastern Brazil, using data from two distinct networks of Fabry‐Perot interferometers measuring the Doppler shift of the 630.0 nm airglow emission. In Brazil, we find direct evidence of a convergent wind field during the period of rapid thermospheric temperature increase associated with the equatorial midnight temperature maximum.
A pseudopotential of $C_{60}^-$ has been constructed from ab-initio quantum-mechanical calculations. Since the obtained pseudopotential can be easily fitted by rather simple analytical approximation it can be effectively used both in classical and quantum molecular dynamics of fullerene-based compounds.
Narayan P. Chapagain, Daniel J. Fisher, John W. Meriwether
et al.
A one‐year dataset spanning March 2011 to March 2012 of coincident observations of nighttime thermospheric zonal neutral winds, equatorial plasma bubble (EPB) velocities, and zonal plasma drifts is used to examine the relationship between the thermosphere and the ionosphere near the geomagnetic equator over Peru. Thermospheric neutral winds are determined by using a bistatic Fabry‐Perot interferometer (FPI) experiment located at Merihill and Nazca in Peru. The ambient plasma drift velocities were obtained using the incoherent scatter radar at the Jicamarca Radio Observatory in Peru. The EPB zonal velocities were estimated utilizing images of the OI 630.0 nm emission recorded by a narrow‐field optical imaging system at the Cerro Tololo Inter‐American Observatory in Chile. The joint analysis of these datasets illustrates that the nighttime and night‐to‐night variations in the zonal neutral winds, EPB velocities, and plasma drifts are well correlated. This consistent result of the local time variations of the neutral winds with that of EPB and plasma drifts illustrates that the F‐region dynamo is, in general, fully activated. However, at times, the magnitude of the EPB velocities and the plasma drifts are different from the neutral winds. It is plausible that such a difference is due either to the effect of polarization electric fields developed inside the EPB or due to the latitudinal gradient of the neutral winds and EPB velocity measurements since the EPB velocities are estimated at a higher latitude, corresponding to an apex altitude of ~400 km, than the wind estimates, which derive from an apex altitude of ~250 km.
This article explored the work of Strijdom van der Merwe, the concept of land art and the notion of the artist's book in the context of the historical and contemporary art market. The premise of the article is the view that if something can be called art, it can also be sold, even if it is an art form that seems 'impossible' to sell, such as land art. This article considers the position of Van der Merwe, the pre-eminent South African land artist, in the somewhat unlikely context, of the South African art market. Van der Merwe is a successful full-time land artist, which is a rare phenomenon in the South African art scene. Indeed in the 1960s, land art was deemed impossible to sell anywhere, and this article explored the extent to which this is still the case today. The research method of the article comprised semi-structured interviews and a literature review. It was argued, in view of Van der Merwe's work, that whilst it may be hue that if something can be called art, it can be sold, then the proviso 'somehow' must be added when referring to seemingly 'impossible art'. Hierdie artikel bied 'n ondersoek na die werk van Strijdom van der Merwe, die gedagte van aardkuns en die kunstenaarsboek in die konteks van die historiese en eietydse kunsmark. Die Stelling dat 'indien iets kuns genoem kan word, kan dit ook verkoop word' word gebruik as vertrekpunt--ook in die geval van kunsvorme wat skynbaar 'onmoontlik' is om te verkoop, soos aardkuns. Hierdie artikel besin oor die werk van Strijdom van der Merwe, die bekendste Suid Afrikaanse aardkunstenaar, binne die ietwat ongewone konteks (vir aardkuns) van die Suid-Afrikaanse kunsmark. Hy is 'n suksesvolle voltydse aardkunstenaar; nogal 'n uitsonderlike verskynsel binne die Suid-Afrikaanse kunsomgewing. Aardkuns is allerwee in die 1960s beskou as 'n 'onmoontlike' kunsvorm om te verkoop, en hierdie artikel ondersoek die geldigheid van hierdie Stelling vir vandag. Die navorsingsmetode van die artikel is semi-gestruktureerde onderhoude en 'n literatuurstudie. My argument is, met verwysing na Van der Merwe se werk, dat die Stelling 'indien iets kuns genoem kan word, dit verkoopbaar is' waar mag wees, maar met die moontlike voorbehoud van 'verkoopbaar--op die een of ander manier'. Introduction Journeys like these are also about the discovering of one self, how you will react to the landscape and the most exciting is how the creative process will unfold as you enter the natural unknown landscape of the island. As I spend most of my time 'outwards' it is very much an 'inward' journey. (Van der Merwe 2009) In this article the work of South Africa's most well-known land artist, Strijdom van der Merwe (b. 1961), and his seemingly 'impossible' to sell art form (land art) are explored with reference to historical and contemporary realties of the art market context (see Art Source South Africa 2010; Ngwenya 2010). Van der Merwe's contribution to the creative research project entitled Transgressions and boundaries of the page, was to combine land art--his primary art form--with conventions from the artist's book Sculpting the Land (2009). It can be argued that the artist's book is a medium that renders Van der Merwe's 'impossible to sell' art form more sellable in the broader art market. Nonetheless, this argument is put forward whilst also taking cognisance of David Paton's (2008) sentiment that the artist's book in itself is still an underappreciated art form in South Africa. In this article, the artist's book will thus be examined alongside land art as a seemingly 'impossible' art form. The premise of this article is that anything that can be called art is sellable and thus collectible. This is hue even of conceptual art forms deemed 'impossible' with reference to the art market context in the 1960s by Messer (1) (1969:31). For the purposes of this article, land art and the artist's book are likewise positioned as 'impossible'. The aim of this article is to inform, and to explore how these two 'impossible' art forms feature in the South African art market. …
Michael Fischer, Ulf Lorenz, Burkhard Schmidt
et al.
By means of quantum-dynamical and classical trajectory calculations of H2+ photodissociation in strong laser fields, it is shown that for certain combinations of pulse durations and intensities the rotational dynamics can lead to centrifugal fragmentation. In that case, the photofragments exhibit characteristic angular distributions. The classical calculations provide a transparent physical picture of this mechanism which is also very well established in collisions between atomic nuclei or liquid droplets: non-rotating systems are stable, whereas rotating systems fragment due to the decrease of the fragmentation barrier with increasing angular momentum.