bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seed size variability has implications for achieving cover cropping goals
Authors: Lounsbury Natalie P. , Warren Nicholas D. , Hobbie Julia , Darby Heather , Ryan Matthew R. , Mortensen David A. , Smith Richard G. 
Published: May 2022

AbstractIt is common to use mass‐based units (e.g., kg ha–1) to describe cover crop seeding rates. However, this convention obscures important information about seed size and resulting plant density in the field, which may be linked to cover crop performance and ecosystem services. Seed counts of 27 lots of commercially available winter rye (Secale cereale L.) spanned a wide range from 28,000 to 50,000 seeds kg–1. If the lots with the lowest and highest seed counts were seeded at a common mass‐based seeding rate of 125 kg ha–1, it would result in a nearly twofold difference in density‐based seeding rate, or 3.0 and 5.6 million live seeds ha–1. Including density‐based metrics such as live seeds per area and resulting in‐field plant density in research will help advance our understanding of cover crop management, and these efforts will make it easier for farmers and policymakers to tailor cover cropping practices for specific goals.
Light emission from Ag cluster films excited by conduction current
Authors: Nepijko S.A. , Fedorovich R.D. , Viduta L.V. , Ievlev D.N. , Schulze W. 
Published: May 2022

AbstractThe light emission spectra obtained for a silver cluster film, excited by the passage of electrical current through it, were measured by the charge‐coupled device (CCD) combined with a monochromator in the spectral range 200 ≑ 1050 nm (6.2 ≑ 1.18 eV). This film is a two‐dimensional ensemble of Ag clusters linked by tunneling on a dielectric substrate. It was shown that the light emission spectra had a number of features, and the shape of spectrum depends on a voltage applied to the film. With increasing the voltage the spectrum starts to extend to high energies. The light emission in the visible spectral region was observed already at 1 V applied to the film, i.e., the photon energy can exceed the excitation energy. It means that this phenomenon is not trivial. In order to explain these results, an assumption about the electron gas heating in metal clusters may be used.
2 + 1‐dimensional black holes with momentum and angular momentum
Authors: Brill D. 
Published: May 2022

AbstractExact solutions of Einstein's equations in 2 + 1‐dimensional anti‐de Sitter space containing any number of black holes are described. In addition to the black holes these spacetimes can possess “internal” structure. Accordingly the generic spacetime of this type depends on a large number of parameters. Half of these can be taken as mass parameters, and the rest as the conjugate (angular) momenta.The time development and horizon structure of some of these spacetimes are sketched.
Quantum phase transitions in electronic systems
Authors: Vojta Thomas 
Published: May 2022

AbstractQuantum phase transitions occur at zero temperature when some non‐thermal control‐parameter like pressure or chemical composition is changed. They are driven by quantum rather than thermal fluctuations. In this review we first give a pedagogical introduction to quantum phase transitions and quantum critical behavior emphasizing similarities with and differences to classical thermal phase transitions. We then illustrate the general concepts by discussing a few examples of quantum phase transitions occurring in electronic systems. The ferromagnetic transition of itinerant electrons shows a very rich behavior since the magnetization couples to additional electronic soft modes which generates an effective long‐range interaction between the spin fluctuations. We then consider the influence of rare regions on quantum phase transitions in systems with quenched disorder, taking the antiferromagnetic transitions of itinerant electrons as a primary example. Finally we discuss some aspects of the metal‐insulator transition in the presence of quenched disorder and interactions.
Synchronization transitions in Josephson arrays: a puzzle and its resolution
Authors: Heath Ted , Wiesenfeld K. 
Published: May 2022

AbstractWe resolve a long standing puzzle concerning synchronization in Josephson junction series arrays. We introduce a modified averaging technique to recover a crucial piece of the collective dynamics. The predicted transition between inphase and splay states is fundamentally changed, introducing the hysteresis long known to be observed in these systems. The analogous problem arises in a general class of globally coupled oscillators.
Making spatial structures by ratchets
Authors: Schimansky‐Geier L. , Seefeld S. , Buchholtz V. 
Published: May 2022

AbstractA chemical circular reaction with three states is considered. An external dichotomic signal switches between two sets of reaction rates. Without signal both sets of rates obey the law of mass action. For finite switching times of the dichotomic perturbation a directed clock wise flow between the three states arises. We show that the directed flow is sufficient to induce a pattern forming process. An optimal switching frequency can be found where clusters form most rapidly.
Magnetic bound states in SmB6
Authors: Riseborough Peter S. 
Published: May 2022

AbstractThe heavy fermion semiconductors such as Ce3Bi4Pt3, YbB12, and SmB6 may be modeled as indirect hybridization gap semiconductors. The magnitudes of the gap are smaller than the gaps predicted by local density functional electronic structure calculations, suggesting strong renormalizations due to electronic correlations. The inelastic neutron scattering spectra Im[χ(q,ω)] are examined within the context of this model. Anomalously sharp and temperature dependent peaks are seen at energies within the indirect gap in the inelastic neutron scattering experiments on SmB6 and YbB12 The in‐gap features are identified as excitations of magnetic bound states, which are induced by residual anti‐ferromagnetic interactions between the renormalized quasi‐particles.
The fundamental fermions and bosons
Authors: Drees J. 
Published: May 2022

AbstractRecent progress in understanding the properties of the fundamental fermions and bosons is presented. The masses and couplings of the heavy Z and W bosons are accurately known from experiments at the CERN electron‐positron storage ring LEP, the SLAC Linear Collider SLC, and the Fermilab proton‐antiproton collider Tevatron. The mass of the top quark has been measured at Fermilab and yields, together with the W mass, an important consistency test of the Minimal Standard Model. Detailed investigations of the properties of quark and gluon jets have been performed, some of the results are summarised. Constraints on the mass of the yet undiscovered Higgs boson are discussed and the perspectives for future searches for new fermions and bosons at the LHC are briefly mentioned.
Quantum mechanics and symmetries
Authors: Wess J. 
Published: May 2022

AbstractSymmetries have always played an important role in physics. With quantum mechanics, however, the interplay between physics and symmetries has reached a new dimension. The very structure of quantum mechanics invites the application of group theoretical methods to an extent that physicists would have been led to invent various concepts of group theory, such as Lie groups, by quantum mechanics had they not been known before.Symmetries are also a direct mediator between experimental facts and the theoretical structure of a theory. This is the case because there is a direct connection between symmetries and conservation laws. Space‐time symmetries are an obvious example. Conservation of energy, momentum and angular momentum are linked to invariance under time translation, space translation and rotation in space.It was in atomic physics that space‐time symmetries became significant, but they are as important in nuclear physics and in all the physics discovered after that. In nuclear physics, however, a new concept of symmetries, symmetries in an internal space, was discovered with the introduction of isospin. All our socalled fundamental models describing what we know about strong‐weak and electromagnetic interactions are built on symmetries in space‐time and internal spaces. These symmetries are not only used to extract information from a theory, they are also used to construct these theories, and this for good reasons. It turned out that only theories possessing such symmetries make sense as quantum field theories. Thus symmetries are not only a good tool to deal with quantum field theoretical models, they are necessary to define such models.Following this line of thought, a new type of symmetry, the socalled supersymmetry, proved to be extremely successfull. Quantum theory seems to have a very deep relation to supersymmetry. Thus it is not surprising that the most promising fundamental models of physics are based on supersymmetry, even when they go beyond a local quantum field theory, as string theory does.
Continuities and discontinuities in Planck's Akt der Verzweiflung
Authors: Darrigol O. 
Published: May 2022

AbstractPlanck's famous communication of December 1900 cannot be understood without taking into account an essential difference between his and Boltzmann's conceptions of the relation between micro‐ and macro‐world. For Boltzmann, macroscopic laws were in principle completely determined by the underlying microscopic dynamics. For Planck, the microscopic dynamics were partly undetermined and had to be supplemented by additional assumptions in order to reach macroscopic laws.Thanks to this leeway, Planck could introduce finite energy‐elements and derive his famous black‐body law without giving up the continuity and determinism of former dynamical theories. The purpose of this paper is to explain the origins, peculiarities, and evolution of Planck's approach; to show how it ultimately yielded the correct black‐body law; and to examine the status of the energy‐elements which Planck thereby introduced.
Photoemission spectroscopy in solids
Authors: Chiang T.‐C. , Seitz F. 
Published: May 2022

AbstractThe photoelectric effect was discovered and explained in terms of quantum physics about a hundred years ago. Today, photoemission spectroscopy using vacuum ultraviolet radiation and x‐rays is an important tool for studying the electronic properties and atomic structure of solids. This paper reviews the development of an understanding of the photoemission process and the basic applications of photoemission spectroscopy in solids, including band structure determination, studies of quasiparticle properties, and core level spectroscopy.
Matter‐antimatter asymmetry of the universe
Authors: Buchmüller W. 
Published: May 2022

AbstractThe asymmetry of the universe between matter and antimatter in the universe is related to neutrino properties due to non‐perturbative processes in the high‐temperature symmetric phase of the standard model. We show that the neutrino masses inferred from the solar and atmospheric neutrino anomalies are consistent with the hypothesis that the observed cosmological matter density has been created in decays of heavy Majorana neutrinos in the early universe.
Finite renormalizations in the Epstein Glaser framework and renormalization of the S‐matrix of Φ4‐theory
Authors: Pinter Gudrun 
Published: May 2022

AbstractA formula describing finite renormalizations is derived in the Epstein‐Glaser formalism and an explicit calculation of finite counterterms in Φ4‐theory is performed. The Zimmermann identities and the action principle for changes of parameters in the interaction are presented independent of the adiabatic limit.
Hamiltonian structure and gauge symmetries of Poincaré gauge theory
Authors: Bagojević M. 
Published: May 2022

AbstractThis is a review of the constrained dynamical structure of Poincaré gauge theory which concentrates on the basic canonical and gauge properties of the theory, including the identification of constraints, gauge symmetries and conservation laws. As an interesting example of the general approach, we discuss the teleparallel formulation of general relativity.
Quantum diffusion and scaling of localized interacting electrons
Authors: Halfpap Ole 
Published: May 2022

AbstractA new numerical method is introduced that enables a reliable study of disorder‐induced localization of interacting particles. It is based on a quantum mechanical time evolution calculation combined with a finite size scaling analysis. The time evolution of up to four particles in one dimension is studied and localization lengths are defined via the long‐time saturation values of the mean radius, the inverse participation ratio and the center of mass extension. A systematic study of finite size effects using the finite size scaling method is performed in order to extract the localization lengths in the limit of an infinite system size. For a single particle, the well‐known scaling of the localization length λ1 with disorder strength W is observed, λ1 ∝ W—2. For two particles, an interaction‐induced delocalization is found, confirming previous results obtained by numerically calculating matrix elements of the two‐particle Green's function: in the limit of small disorder, the localization length increases with decreasing disorder as λ2 ∝ W—4 and can be much larger than &#60;$&#62;\mitlambda λ1. For three and four particles, delocalization is even stronger. Based on analytical arguments, an upper bound for the n‐particle localization length λn is derived and shown to be in agreement with the numerical data, λn ∝ λ1. Although the localization length increases superexponentially with particle number and can become arbitrarily large for small disorder, it does not diverge for finite λ1 and n. Hence, no extendedstates exist in one dimension, at least for spinless fermions.
Dimple‐assisted dewetting: heterogeneous nucleation in undercooled wetting films
Authors: Blossey Ralf 
Published: May 2022

AbstractUndercooled wetting films near a first‐order wetting transition exhibit an unusually long lifetime: the thermal nucleation barrier for formation of a critical hole in a film of thickness F diverges according to Γ ∼ exp (ℰc/kBT) where the excess free energy ℰc ∼ Fζ with ζ ≥ 2. Localized perturbations of the liquid‐vapor interface (‘dimples’) are shown to be a useful tool in reducing Γ in a controlled way: they act as heterogeneous nucleation centers for thermal critical nuclei. For 4He wetting films on weak‐binding alkali substrates (Cs, Rb) dimples can be generated either by vortices in a superfluid film or by surface electrons. The theory of the heterogeneous nucleation process initiated by the presence of surface dimples (‘dimple‐assisted dewetting’) is developed, accompanied by quantitative predictions for experiment.
Fluctuation effects in disordered Peierls systems
Authors: Bartosch Lorenz 
Published: May 2022

AbstractWe review the density of states (DOS) and related quantities of quasi one‐dimensional disordered Peierls systems in which fluctuation effects of a backscattering potential play a crucial role. The low‐energy behavior of non‐interacting fermions which are subject to a static random backscattering potential will be described by the strictly one‐dimensional fluctuating gap model (FGM). Recently, the FGM has also been used to explain the pseudogap phenomenon in high‐Tc superconductors. We develop a non‐perturbative method which allows for a simultaneous calculation of the DOS and inverse localization length for an arbitrary given disorder potential by solving a simple initial value problem. In the white noise limit, we recover all known results by solving a Fokker‐Planck equation. For the physically interesting case of finite correlation lengths, we use analytical and numerical methods to show that a complex order parameter leads to a suppression of the DOS, i.e. a pseudogap, and that for a real order parameter this pseudogap is overshadowed by a singularity in the DOS. We will also consider the case of classical phase fluctuations which applies to low temperatures where amplitude fluctuations are frozen out. For this regime we present analytic results for the DOS, the inverse localization length, the specific heat, and the Pauli susceptibility.
Wave phenomena in low‐rate plastic flow of solids
Authors: Zuev Lev B. 
Published: May 2022

AbstractAn investigation of plastic flow localization patterns (waves) which are ordered in space and evolve with time has been performed for a wide range of metals and alloys. These waves are found to have the following basic features: the dependence of propagation rate on work hardening coefficient, dispersion law and scale effect. The possibility of addressing plastic flow localization as a self‐organization process occurring in a deforming medium is considered. A set of equations appropriate for the description of local flow nuclei is discussed. Consideration is given to a change‐over from one local strain pattern to another in accordance with the respective stages of flow. Proposed is a model for interpreting the large‐scale periodicities exhibited by the distribution of localized strain nuclei.
Many‐body Green's function theory for thin ferromagnetic films: exact treatment of the single‐ion anisotropy
Authors: Fröbrich P. , Kuntz P.J. , Saber M. 
Published: May 2022

AbstractA theory for the magnetization of ferromagnetic films is formulated within the framework of many‐body Green's function theory which considers all components of the magnetization. The model Hamiltonian includes a Heisenberg term, an external magnetic field, a second‐ and fourth‐order uniaxial single‐ion anisotropy, and the magnetic dipole‐dipole coupling. The single‐ion anisotropy terms can be treated exactlyby introducing higher‐order Green's functions and subsequently taking advantage of relations between products of spin operators which leads to an automatic closure of the hierarchy of the equations of motion for the Green's functions with respect to the anisotropy terms. This is an improvement on the method of our previous work, which treated the corresponding terms only approximately by decoupling them at the level of the lowest‐order Green's functions. RPA‐like approximations are used to decouple the exchange interaction terms in both the low‐order and higher‐order Green's functions. As a first numerical example we apply the theory to a monolayer for spin S = 1 in order to demonstrate the superiority of the present treatment of the anisotropy terms over the previous approximate decouplings.
Ring currents effect on the dielectric function of cylindrical nano‐organic materials
Authors: Pleutin Stéphane , Ovchinnikov Alexander 
Published: May 2022

AbstractWe review recent results on the behaviour of the dielectric function of cylindrical nano‐organic materials at very low frequencies in a magnetic field. For cylindrical structures — such as carbon nanotubes — the polarisability is shown to be a discontinuous function of a longitudinal magnetic field where plateau‐like regions are separated by sudden jumps or peaks. A relation is pointed out between each discontinuity in the polarisability and the cross‐over between ground and first excited states induced by the magnetic field. This one to one correspondence suggests to use measurements of the dielectric function in an applied magnetic field in order to obtain informations about the electronic structures of cylindrical nanostructures. In addition, it is shown, by studying finite graphene layers, that the measurement of the polarisability in a magnetic field could be a powerful way for detecting possible edge‐states in amorphous carbon materials such as activated carbon fibres. Finally, the importance of the electron‐electron interaction is emphasised by discussing examples of strongly interacting electrons on rings or cylinders, in the limit of infinite interaction.
Infrared absorption spectra studies in (NaNO3–NaNO2) system
Authors: Hammad Talaat Moussa 
Published: May 2022

AbstractA complete infrared study of the mixed crystal system of NaNO3 and NaNO2 is carried out in the region 600—3000 cm—1 at room temperature. The study includes fundamental internal normal vibrations of the NO—2 and NO—3 ions. The IR spectra, spectral band shape intensities, combination modes, and frequencies of the internal modes were studied as a function of NO—3 ion concentration. Special attention is paid to the bending mode, the combination mode, and a symmetric stretching mode.
Neutrino masses and particle physics beyond the standard model
Authors: Päs H. 
Published: May 2022

AbstractThe evidence for non‐vanishing neutrino masses from solar and atmospheric neutrinos provides the first solid hint towards physics beyond the standard model. A full reconstruction of the neutrino spectrum may well provide a key to the theoretical structures underlying the standard model such as supersymmetry, grand unification or extra space dimensions. In this article we discuss the impact of absolute neutrinos masses on physics beyond the standard model. We review the information obtained from neutrino oscillation data and discuss the prospects of the crucial determination of the absolute neutrino mass scale, as well as the intriguing connection with the Z‐burst model for extreme‐energy cosmic rays.
A supersymmetric extension of quantum gauge theory
Authors: Grigore D.R. , Scharf G. 
Published: May 2022

AbstractWe consider a supersymmetric extension of quantum gauge theory based on a vector multiplet containing supersymmetric partners of spin 3/2 for the vector fields. The constructions of the model follows closely the usual construction of gauge models in the Epstein‐Glaser framework for perturbative field theory. Accordingly, all the arguments are completely of quantum nature without reference to a classical supersymmetric theory. As an application we consider the supersymmetric electroweak theory. The resulting self‐couplings of the gauge bosons agree with the standard model up to a divergence.
The temperature dependence of saturation magnetization of γ‐Fe2O3/SiO2 magnetic nanocomposite
Authors: Caizer C. , Hrianca I. 
Published: May 2022

AbstractThe saturation magnetization of ferrimagnetic nanoparticles of γ‐Fe2O3 that are isolated in an amorphous SiO2 matrix, has a high increase when the temperature decreases from 300 to 77K. In this case, the relative variation (69.7 magnetization corresponding to bulk ferrite (9.5 is attributed to the narrowing of the paramagnetic layer that exists at the surface of nanoparticles; with the decrease of temperature, the mean magnetic diameter, and implicitly the magnetic moment of the particles increases, which in turn leads to an increase of the saturation magnetization. The existence of the paramagnetic layer is a result of the modification of the superexchange interaction between iron ions at the nanoparticle surface, due to the distortion of the crystalline network in the presence of the silica matrix. Based on the experimental results we propose a core‐shell model that explains the abnormal increase of the saturation magnetization of γ‐Fe2O3 nanoparticles dispersed in a silica matrix compared to bulk γ‐Fe2O3.