Generalized seniority for the shell model with realistic interactions

The generalized seniority scheme has long been proposed as a means of dramatically reducing the dimensionality of nuclear shell model calculations, when strong pairing correlations are present. However, systematic benchmark calculations, comparing results obtained in a model space truncated according to generalized seniority with those obtained in the full shell model space, are required to assess the viability of this scheme. Here, a detailed comparison is carried out, for semimagic nuclei taken in a full major shell and with realistic interactions. The even-mass and odd-mass Ca isotopes are treated in the generalized seniority scheme, for generalized seniority v<=3. Results for level energies, orbital occupations, and electromagnetic observables are compared with those obtained in the full shell model space.Comment: 13 pages, 8 figures; published in Phys. Rev.

Recursive relations for a quiver gauge theory

We study the recursive relations for a quiver gauge theory with the gauge group $SU(N_1)\times SU(N_2)$ with bifundamental fermions transforming as $(N_1,\bar{N_2})$. We work out the recursive relation for the amplitudes involving a pair of quark and antiquark and gluons of each gauge group. We realize directly in the recursive relations the invariance under the order preserving permutations of the gluons of the first and the second gauge group. We check the proposed relations for MHV, 6-point and 7-point amplitudes and find the agreements with the known results and the known relations with the single gauge group amplitudes. The proposed recursive relation is much more efficient in calculating the amplitudes than using the known relations with the amplitudes of the single gauge group.Comment: 33 pages and 2 figures, minor correction

Bound States and Critical Behavior of the Yukawa Potential

We investigate the bound states of the Yukawa potential $V(r)=-\lambda \exp(-\alpha r)/ r$, using different algorithms: solving the Schr\"odinger equation numerically and our Monte Carlo Hamiltonian approach. There is a critical $\alpha=\alpha_C$, above which no bound state exists. We study the relation between $\alpha_C$ and $\lambda$ for various angular momentum quantum number $l$, and find in atomic units, $\alpha_{C}(l)= \lambda [A_{1} \exp(-l/ B_{1})+ A_{2} \exp(-l/ B_{2})]$, with $A_1=1.020(18)$, $B_1=0.443(14)$, $A_2=0.170(17)$, and $B_2=2.490(180)$.Comment: 15 pages, 12 figures, 5 tables. Version to appear in Sciences in China

A comparison of efficient methods for the computation of Born gluon amplitudes

We compare four different methods for the numerical computation of the pure gluonic amplitudes in the Born approximation. We are in particular interested in the efficiency of the various methods as the number n of the external particles increases. In addition we investigate the numerical accuracy in critical phase space regions. The methods considered are based on (i) Berends-Giele recurrence relations, (ii) scalar diagrams, (iii) MHV vertices and (iv) BCF recursion relations.Comment: 20 page

A comparison of proximal femoral locking compression plates with dynamic hip screws in extracapsular femoral fractures

AbstractIntroductionThe potential value of proximal femoral locking compression plate (PFLCP) for extracapsular femoral fractures has been discussed in several case reports; however, clinical control studies are lacking. Therefore, we performed a case control study to assess: (1) If PFLCP offers better functional results and fewer complications than dynamic hip screws (DHS)? (2) Which kind of extracapsular femoral fractures would benefit from PFLCP fixation?HypothesisThe PFLCP fixation offers better functional results and fewer complications than the DHS for the treatment of extracapsular fractures.Patients and methodsA total of 83 patients with extracapsular femoral fractures were recruited. Forty-one patients underwent PFLCP fixation, and 42 patients underwent DHS fixation. Patient information, operative time, blood loss, functional level (as assessed by Sanders’ traumatic hip rating scale), bone union, and implant complications were compared for the two treatment groups.ResultsPatients with stable intertrochanteric fractures who underwent PFLCP fixation demonstrated shorter bone union time than the DHS fixation group (3.3±0.2 vs. 4.3±0.1 month; P<0.0001); however, both groups had 100% bone union and good to excellent scores on Sanders’ traumatic hip rating scale (P=1.000). Patients with unstable intertrochanteric fractures who underwent PFLCP fixation experienced greater blood loss (619.0±23.9 vs. 474.1±19.8ml; P<0.0001), which was mainly due to the need for open reduction (64.3% vs. 12.5%; P=0.003), compared to the DHS fixation group. No differences were identified with respect to bony union, functional level, or complications. Patients with subtrochanteric fractures who underwent PFLCP fixation demonstrated significantly shorter operative times (82.1±4.3 vs. 102.2±2.2minutes; P<0.0001), less blood loss (751.8±25.4 vs. 987.6±32.0ml; P<0.0001), shorter bone union times (5.2±0.4 vs. 8.8±1.0 month; P=0.006), more good to excellent Sanders’ traumatic hip rating scale scores (92.9% vs. 55.5%; P=0.009), and fewer complications (14.2% vs. 66.6%; P=0.005) than the DHS fixation group.ConclusionPFLCP fixation offers better functional outcomes and fewer complications for subtrochanteric femoral fractures but not for intertrochanteric femoral fractures.Levels of evidenceCase control study, level III

Using Muonic Hydrogen in Optical Spectroscopy Experiment to Detect Extra Dimensions

Considering that gravitational force might deviate from Newton's inverse-square law (ISL) and become much stronger in small scale, we propose a kind of optical spectroscopy experiment to detect this possible deviation and take electronic, muonic and tauonic hydrogen atoms as examples. This experiment might be used to indirectly detect the deviation of ISL down to nanometer scale and to explore the possibility of three extra dimensions in ADD's model, while current direct gravity tests cannot break through micron scale and go beyond two extra dimensions scenario.Comment: 9 pages, 2 figures. To appear in IJT