Which Fine-Tuning Arguments Are Fine?

Fine-tuning arguments are a frequent find in the literature on quantum field theory. They are based on naturalness—an aesthetic criterion that was given a precise definition in the debates on the Higgs mechanism. We follow the history of such definitions and of their application at the scale of electroweak symmetry breaking. They give rise to a special interpretation of probability, which we call Gedankenfrequency. Finally, we show that the argument from naturalness has been extended to comparing different models of the physics beyond the Standard Model and that naturalness in this case can at best be understood a socio-historic heuristic.     

Effects of acceleration on the collision of particles in the rotating black hole spacetime

We study the collision of two geodesic particles in the accelerating and rotating black hole spacetime and probe the effects of the acceleration of black hole on the center-of-mass energy of the colliding particles and on the high-velocity collision belts. We find that the dependence of the center-of-mass energy on the acceleration in the near event-horizon collision is different from that in the near acceleration-horizon case. Moreover, the presence of the acceleration changes the shape and position of the high-velocity collision belts. Our results show that the acceleration of black holes brings about richer physics for the collision of particles.     

Wave functions and decay constants of <Emphasis Type="Italic">B</Emphasis> and <Emphasis Type="Italic">D</Emphasis> mesons in the relativistic potential model

With the decay constants of D and D _s mesons measured in experiment recently, we revisit the study of the bound states of quark and antiquark in B and D mesons in the relativistic potential model. The relativistic bound state wave equation is solved numerically. The masses, decay constants and wave functions of B and D mesons are obtained. Both the masses and decay constants obtained here can be seen as consistent with the experimental data. The wave functions can be used in the study of B and D meson decays.     

Gender effect on neurodegeneration and myelin markers in an animal model for multiple sclerosis

Background  

Multiple sclerosis (MS) varies considerably in its incidence and progression in females and males. In spite of clinical evidence, relatively few studies have explored molecular mechanisms possibly involved in gender-related differences. The present study describes possible cellular- and molecular-involved markers which are differentially regulated in male and female rats and result in gender-dependent EAE evolution and progression. Attention was focused on markers of myelination (MBP and PDGFαR) and neuronal distress and/or damage (GABA synthesis enzymes, GAD65 and GAD67, NGF, BDNF and related receptors), in two CNS areas, i.e. spinal cord and cerebellum, which are respectively severely and mildly affected by inflammation and demyelination. Tissues were sampled during acute, relapse/remission and chronic phases and results were analysed by two-way ANOVA.     

Near generalized balanced tournament designs with block sizes 4 and 5

A near generalized balanced tournament design, or an NGBTD(k,m) in short, is a (km + 1, k, k − 1)-BIBD defined on a (km +1)-set V. Its blocks can be arranged into an m × (km + 1) array in such a way that (1) the blocks in every column of the array form a partial parallel class partitioning V[x] for some point x, and (2) every element of V is contained in precise k cells of each row. In this paper, we completely solve the existence of NGBTD(4,m) and almost completely solve the existence of NGBTD(5,m) with four exceptions.     

Crystal growth,spectroscopic characterization and laser performance of Nd:Lu<Subscript>0.33</Subscript>Y<Subscript>0.36</Subscript>Gd<Subscript>0.3</Subscript>VO<Subscript>4</Subscript> crystal

A new three-matrix mixed vanadate crystal Nd:Lu_0.33Y_0.36Gd_0.3VO₄ (Nd:LuYGdVO₄) crystal was grown by the Czochralski method. Room temperature absorption and fluorescence spectra of the Nd:LuYGdVO₄ crystals were measured and the spectroscopic parameters were calculated by the Judd-Ofelt theory. The intensity parameters of the Nd:LuYGdVO₄ crystal were Ω₂ = 9.736 × 10⁻²⁰ cm², Ω₄ = 4.179 × 10⁻²⁰ cm², Ω₆ = 8.020 × 10⁻²⁰ cm² and the stimulate emission cross section was 5.3 × 10⁻¹⁹ cm². Diodepumped actively Q-switched and passively Q-switched Nd:LuYGdVO₄ and Nd:Lu_0.14Y_0.86VO₄ lasers at 1.06 μm were demonstrated. The results indicate that, for both actively and passively Q-switched lasers, the Nd:LuYGdVO₄ lasers can generate shorter pulse width with higher peak power than the Nd:Lu_0.14Y_0.86VO₄ lasers at the same cavity conditions.     

Three-dimensional simulation of laser–plasma-based electron acceleration

A sequential three-dimensional (3D) particle-in-cell simulation code PICPSI-3D with a user friendly graphical user interface (GUI) has been developed and used to study the interaction of plasma with ultrahigh intensity laser radiation. A case study of laser–plasma-based electron acceleration has been carried out to assess the performance of this code. Simulations have been performed for a Gaussian laser beam of peak intensity 5 × 10¹⁹ W/cm² propagating through an underdense plasma of uniform density 1 × 10¹⁹ cm^− 3, and for a Gaussian laser beam of peak intensity 1.5 × 10¹⁹ W/cm² propagating through an underdense plasma of uniform density 3.5 × 10¹⁹ cm^− 3. The electron energy spectrum has been evaluated at different time-steps during the propagation of the laser beam. When the plasma density is 1 × 10¹⁹ cm^− 3, simulations show that the electron energy spectrum forms a monoenergetic peak at ~14 MeV, with an energy spread of ±7 MeV. On the other hand, when the plasma density is 3.5 × 10¹⁹ cm^− 3, simulations show that the electron energy spectrum forms a monoenergetic peak at ~23 MeV, with an energy spread of ±7.5 MeV.     

A Study of the Intrinsic Autofluorescence of Poly (ethylene glycol)-co-(<Subscript><Emphasis Type="Italic">L</Emphasis></Subscript>-Lactic acid) Diacrylate

Poly (ethylene glycol)-co-( _L -Lactic acid) diacrylate (PEG-PLLA-DA) copolymers have been extensively investigated for a number of applications in medicine. PEG-PLLA-DA is biodegradable and the human body can process its degradation products. In this study, we describe the autofluorescence of PEG-PLLA-DA copolymers and compared it to the fluorescence of poly(ethylene glycol) diacrylate (PEG-DA) and the precursor molecules used for their synthesis. In addition, we examined the influence of pH on the fluorescence spectra. We found that PEG-PLLA-DA exhibits higher fluorescence than PEG-DA and all reagents involved in the synthesis of PEG-PLLA-DA. The fluorescence of PEG-PLLA-DA was affected by pH with fluorescence decreasing at high pH values. At high pH, PEG-PLLA-DA could not polymerize into hydrogels and exhibited a dramatic decrease in autofluorescence, suggesting that hydrolysis of the ester bond affected its autofluorescence. At low pH, PEG-PLLA-DA exhibited higher fluorescence and it was able to form crosslinked hydrogels. The autofluorescence of PEG-PLLA-DA could be exploited to monitor polymer degradation and material structure without the need to introduce exogenous fluorescent probes. The origin of fluorescence is not clear at this point in time but it appears to result from a synergetic effect of both lactate units and diacrylate groups in the PEG-PLLA-DA backbone. The observed autofluorescence of PEG-PLLA-DA persists after reaction of the acrylate groups in the polymerization reaction. This autofluorescence is advantageous because it could assist in the study of polymers used for drug delivery and tissue engineering applications.     

Extended Birkhoff’s theorem in <Emphasis Type="Italic">f</Emphasis>(<Emphasis Type="Italic">T</Emphasis>) gravity

f(T) theory, a generally modified teleparallel gravity, has been proposed as an alternative gravity model to account for the dark energy phenomena. Following our previous work [Xin-he Meng and Ying-bin Wang, Eur. Phys. J. (2011), ], we prove that Birkhoff’s theorem holds in a more general context, specifically with the off diagonal tetrad case, in this communication letter. Then, we discuss, respectively, the results of the external vacuum and internal gravitational field in the f(T) gravity framework, as well as the extended meaning of this theorem. We also investigate the validity of Birkhoff’s theorem in the frame of f(T) gravity via a conformal transformation by regarding the Brans–Dicke-like scalar as effective matter, and study the equivalence between both Einstein frame and Jordan frame.     

Optimal control of Markovian jump processes with partial information and applications to a parallel queueing model

We consider a stochastic control problem over an infinite horizon where the state process is influenced by an unobservable environment process. In particular, the Hidden-Markov-model and the Bayesian model are included. This model under partial information is transformed into an equivalent one with complete information by using the well-known filter technique. In particular, the optimal controls and the value functions of the original and the transformed problem are the same. An explicit representation of the filter process which is a piecewise-deterministic process, is also given. Then we propose two solution techniques for the transformed model. First, a generalized verification technique (with a generalized Hamilton–Jacobi–Bellman equation) is formulated where the strict differentiability of the value function is weaken to local Lipschitz continuity. Second, we present a discrete-time Markovian decision model by which we are able to compute an optimal control of our given problem. In this context we are also able to state a general existence result for optimal controls. The power of both solution techniques is finally demonstrated for a parallel queueing model with unknown service rates. In particular, the filter process is discussed in detail, the value function is explicitly computed and the optimal control is completely characterized in the symmetric case.