704 research outputs found
Supersymmetric Solutions in Four-Dimensional Off-Shell Curvature-Squared Supergravity
Off-shell formulations of supergravities allow one to add closed-form
higher-derivative super-invariants that are separately supersymmetric to the
usual lower-derivative actions. In this paper we study four-dimensional
off-shell N=1 supergravity where additional super-invariants associated with
the square of the Weyl tensor and the square of the Ricci scalar are included.
We obtain a variety of solutions where the metric describes domain walls,
Lifshitz geometries, and also solutions of a kind known as gyratons. We find
that in some cases the solutions can be supersymmetric for appropriate choices
of the parameters. In some solutions the auxiliary fields may be imaginary. One
may reinterpret these as real solutions in an analytically-continued theory.
Since the supersymmetry transformation rules now require the gravitino to be
complex, the analytically-continued theory has a "fake supersymmetry" rather
than a genuine supersymmetry. Nevertheless, the concept of
pseudo-supersymmetric solutions is a useful one, since the Killing spinor
equations provide first-order equations for the bosonic fields.Comment: 28 page
Optimal Sliding Mode Control for a Class of Uncertain Nonlinear Systems Based on Feedback Linearization
The surface plasmon enhancement effect on adsorbed molecules at elevated temperatures
The surface plasmon enhancement effect on adsorbed molecules at elevated substrate temperatures is studied theoretically using surface enhanced Raman scattering (SERS) as an example. The surface structure is idealized to be a monodisperse spherical particle with its nonlocal dielectric response accounted for. The temperature effects are modeled using a temperature-dependent collision frequency in the Drude model. Numerical results show that only a small decrease in the SERS enhancement ratio occurs for temperatures up to the melting point of the substrate, even for scattering close to the surface plasmon resonance frequency of the metal. More definitive results are subjected to more realistic modeling as well as systematic experimental studies. The implication of this result to other surface photochemical processes is discussed
A Mixing Coupling Scheme for Spectra of Singly Heavy Baryons with Spin-1 Diquarks in P-waves
A new scheme of state classification is proposed and applied to analyze
masses of the heavy baryons , and
in P-waves. The results confirm all excited and
baryons reported recently by LHCb to be bound states of a P-wave -diquark
and a respective charm or bottom quark, and thereby predict Regge trajectories
for more excited and baryons. We suggest one excited
{} state to be unseen by LHCb around MeV,
and predict P-wave masses of all spin-partners of the odd-parity baryons
and
/. A computation is further given in
a relativized potential quark models to explain matched values of spin
couplings of all considered baryons, by which a scaling law for these spin
couplings is discussed.Comment: 28 pages, 3 figures in total, with one new figure (FIG. 3) and one
new section (Section VI) added in this enlarged version(V3). Due to twice
extensions (Section V and Section VI added) including two newly added
figures(FIG. 2 and FIG. 3), we also changed the title correspondingl
The difference of boundary effects between Bose and Fermi systems
In this paper, we show that there exists an essential difference of boundary
effects between Bose and Fermi systems both for Dirichlet and Neumann boundary
conditions: at low temperatures and high densities the influence of the
boundary on the Bose system depends on the temperature but is independent of
the density, but for the Fermi case the influence of the boundary is
independent of the temperature but depends on the density, after omitting the
negligible high-order corrections. We also show that at high temperatures and
low densities the difference of the influence of the boundary between Bose and
Fermi systems appears in the next-to-leading order boundary contribution, and
the leading boundary contribution is independent of the density. Moreover, for
calculating the boundary effects at high temperatures and low densities, since
the existence of the boundary modification causes the standard virial expansion
to be invalid, we introduce a modified virial expansion.Comment: 8 page
(2,4-Dihydroxybenzylidene)dimethylammonium dichlorophosphinate
In the title compound, C9H12NO2
+·Cl2PO2
−, the molecular skeleton of the cation is nearly planar with an r.m.s. deviation of 0.0336 Å. In the crystal structure, intermolecular O—H⋯O hydrogen bonds link cations and anions into chains running along [10]
2-(3-Pyridinio)benzimidazolium pentachloridobismuthate(III) monohydrate
In the title compound, (C12H11N3)[BiCl5]·H2O, the BiIII atom is coordinated by five chloride anions in a distorted square-pyramidal geometry. The planar imidazole ring system [maximum deviation = 0.012 (3) Å] is oriented at a dihedral angle of 6.08 (5)° with respect to the protonated pyridine ring. An O—H⋯Cl interaction links the water molecule to the dianion. In the crystal structure, intermolecular O—H⋯Cl, N—H⋯O and N—H⋯Cl interactions link the molecules into a three-dimensional network
Accurate description of the optical response of a multilayered spherical system in the long wavelength approximation
The optical response of a multilayered spherical system of unlimited number of layers (a “matryoshka”) in the long wavelength limit can be accounted for from the knowledge of the static multipole polarizability of the system to first-order accuracy. However, for systems of ultrasmall dimensions or systems with sizes not-too-small compared to the wavelength, this ordinary quasistatic long wavelength approximation (LWA) becomes inaccurate. Here we introduce two significant modifications of the LWA for such a nanomatryoshka in each of the two limits: the nonlocal optical response for ultrasmall systems (\u3c10 \u3enm), and the “finite-wavelength corrections” for systems ∼100 nm. This is accomplished by employing the previous work for a single-layer shell, in combination with a certain effective-medium approach formulated recently in the literature. Numerical calculations for the extinction cross sections for such a system of different dimensions are provided as illustrations for these effects. This formulation thus provides significant improvements on the ordinary LWA, yielding enough accuracy for the description of the optical response of these nanoshell systems over an appreciable range of sizes, without resorting to more involved quantum mechanical or fully electrodynamic calculations
- …