Search results for "Field Theory"

Resolution of singularities for multi-loop integrals

2007

We report on a program for the numerical evaluation of divergent multi-loop integrals. The program is based on iterated sector decomposition. We improve the original algorithm of Binoth and Heinrich such that the program is guaranteed to terminate. The program can be used to compute numerically the Laurent expansion of divergent multi-loop integrals regulated by dimensional regularisation. The symbolic and the numerical steps of the algorithm are combined into one program.

Design of 3d–4f molecular squares through the [Fe{(HB(pz)3)}(CN)3]− metalloligand

2018

A new series of {FeIII2LnIII2} heterobimetallic squares of general formula [FeIII{HB(pz)3}(CN)(μ-CN)2Ln(pyim)x(NO3)2(H2O)y]2·zH2O [Ln = La (1), Gd (2), Tb (3) and Dy (4); {HB(pz)3}− = hydrotris(pyrazolyl)borate and pyim = 2-(1H-imidazol-2-yl)pyridine; x = 2, y = 0 (1), x = y = 1 (2–4) and z = 10 (1), 6 (2), 2.76 (3), 4 (4)] were synthesized by reacting the low-spin [FeIII{HB(pz)3}(CN)3]− complex anion with the preformed [LnIII(pyim)x(NO3)2(H2O)y]+ complex cation [formed in situ by mixing the lanthanide(III) salt and the pyim ligand]. Single-crystal X-ray diffraction shows that 1–4 crystallize in the P triclinic space group, 2–4 being isomorphous. In all cases, the structure comprises neutra…

Lanthanoid single-ion magnets based on polyoxometalates with a 5-fold symmetry: The series [LnP5W30O110]12– (Ln3+ = Tb, Dy, Ho, Er, Tm, and Yb)

2012

A robust, stable and processable family of mononuclear lanthanoid complexes based on polyoxometalates (POMs) that exhibit single-molecule magnetic behavior is described here. Preyssler polyanions of general formula [LnP 5W 30O 110] 12- (Ln 3+ = Tb, Dy, Ho, Er, Tm, and Yb) have been characterized with static and dynamic magnetic measurements and heat capacity experiments. For the Dy and Ho derivatives, slow relaxation of the magnetization has been found. A simple interpretation of these properties is achieved by using crystal field theory. © 2012 American Chemical Society.

Magnetic properties of the layered lanthanide hydroxide series Y(x)Dy(8-x)(OH)20Cl4·6H2O: from single ion magnets to 2D and 3D interaction effects.

2015

The magnetic properties of layered dysprosium hydroxides, both diluted in the diamagnetic yttrium analogous matrix (LYH:0.04Dy), and intercalated with 2,6-naphthalene dicarboxylate anions (LDyH-2,6-NDC), were studied and compared with the recently reported undiluted compound (LDyH = Dy8(OH)20Cl4·6H2O). The Y diluted compound reveals a single-molecule magnet (SMM) behavior of single Dy ions, with two distinct slow relaxation processes of the magnetization at low temperatures associated with the two main types of Dy sites, 8- and 9-fold coordinated. Only one relaxation process is observed in both undiluted LDyH and intercalated compounds as a consequence of dominant ferromagnetic Dy-Dy intera…

Mononuclear Lanthanide Complexes: Use of the Crystal Field Theory to Design Single-Ion Magnets and Spin Qubits

2015

Supersymmetric Indices of 3d S-fold SCFTs

2019

Enhancement of global symmetry and supersymmetry in the infrared is one of the most intriguing phenomena in quantum field theory. We investigate such phenomena in a large class of three dimensional superconformal field theories, known as the S-fold SCFTs. Supersymmetric indices are computed for a number of theories containing small rank gauge groups. It is found that indices of several models exhibit enhancement of supersymmetry at the superconformal fixed point in the infrared. Dualities between S-fold theories that have different quiver descriptions are also analysed. We explore a new class of theories with a discrete global symmetry, whose gauge symmetry in the quiver has a different glo…

The Heisenberg dynamics of spin systems: A quasi*‐algebras approach

1996

The problem of the existence of the thermodynamical limit of the algebraic dynamics for a class of spin systems is considered in the framework of a generalized algebraic approach in terms of a special class of quasi*-algebras, called CQ*-algebras. Physical applications to (almost) mean-field models and to bubble models are discussed. © 1996 American Institute of Physics.

Intramolecular phase separation of copolymer "bottle brushes": No sharp phase transition but a tunable length scale

2006

A lattice model for a symmetrical copolymer "bottle brush" molecule, where two types (A,B) of flexible side chains are grafted with one chain end to a rigid backbone, is studied by a variant of the pruned-enriched Rosenbluth method (PERM), allowing for simultaneous growth of all side chains in the Monte Carlo sampling. Choosing repulsive binary interactions between unlike monomers and varying the solvent quality, it is found that phase separation into an $A$-rich part of the cylindrical molecule and a $B$-rich part can occur only locally. Long range order (in the direction of the backbone) does not occur, and hence the transition from the randomly mixed state of the bottle brush to the phas…

Static and non-static vector screening masses

2016

Thermal screening masses of the conserved vector current are calculated both in a weak-coupling approach and in lattice QCD. The inverse of a screening mass can be understood as the length scale over which an external electric field is screened in a QCD medium. The comparison of screening masses both in the zero and non-zero Matsubara frequency sectors shows good agreement of the perturbative and the lattice results. Moreover, at $T\approx 508\mathrm{MeV}$ the lightest screening mass lies above the free result ($2\pi T$), in agreement with the $\mathcal{O}(g^2)$ weak-coupling prediction.

Excited state decay of cyclometalated polypyridine ruthenium complexes: insight from theory and experiment.

2016

Deactivation pathways of the triplet metal-to-ligand charge transfer ((3)MLCT) excited state of cyclometalated polypyridine ruthenium complexes with [RuN5C](+) coordination are discussed on the basis of the available experimental data and a series of density functional theory calculations. Three different complex classes are considered, namely with [Ru(N^N)2(N^C)](+), [Ru(N^N^N)(N^C^N)](+) and [Ru(N^N^N)(N^N^C)](+) coordination modes. Excited state deactivation in these complex types proceeds via five distinct decay channels. Vibronic coupling of the (3)MLCT state to high-energy oscillators of the singlet ground state ((1)GS) allows tunneling to the ground state followed by vibrational rela…