Torsion as electromagnetism and spin

We show that it is possible to formulate the classical Einstein-Maxwell-Dirac theory of spinors interacting with the gravitational and electromagnetic fields as the Einstein-Cartan-Kibble-Sciama theory with the Ricci scalar of the traceless torsion, describing gravity, and the torsion trace acting as the electromagnetic potential.Comment: 6 pages; published versio

Ambiguity of gamma-ray tracking of "two-interaction" events

Tracking of gamma-ray interactions in germanium detectors can allow reconstruction of the photon paths, and is useful for many applications. Scrutiny of the kinematics and geometry of gamma rays which are Compton scattered only once prior to full absorption reveals that there are cases where even perfect spatial and energy resolution cannot resolve the true interaction sequence and consequently gamma-ray tracks cannot be reconstructed. The photon energy range where this ambiguity exists is from 255 keV to around 700 keV. This is a region of importance for nuclear structure research where two-point interactions are probable.Comment: 8 pages, 2 figure

Four-fermion interaction from torsion as dark energy

The observed small, positive cosmological constant may originate from a four-fermion interaction generated by the spin-torsion coupling in the Einstein-Cartan-Sciama-Kibble gravity if the fermions are condensing. In particular, such a condensation occurs for quark fields during the quark-gluon/hadron phase transition in the early Universe. We study how the torsion-induced four-fermion interaction is affected by adding two terms to the Dirac Lagrangian density: the parity-violating pseudoscalar density dual to the curvature tensor and a spinor-bilinear scalar density which measures the nonminimal coupling of fermions to torsion.Comment: 6 pages; published versio

Mirror energy differences in the A=31 mirror nuclei, S31 and P31, and their significance in electromagnetic spin-orbit splitting

Excited states in S31 and P31 were populated in the C12(Ne20,n) and C12(Ne20,p) reactions, respectively, at a beam energy of 32 MeV. High spin states of positive and negative parity have been observed in S31 for the first time, and the yrast scheme of P31 has been extended. Large mirror energy differences between the first 9/2- and 13/2- states were observed, but only small differences for the first 7/2- and 11/2- levels. The significance of these observations is discussed in relation to the electromagnetic spin-orbit effect and the relative binding energy of the levels

Lifetime measurements of triaxial strongly deformed bands in Tm163

With the Doppler Shift Attenuation Method, quadrupole transition moments Qt were determined for the two recently proposed triaxial strongly deformed (TSD) bands in Tm163. The measured Qt values indicate that the deformation of these bands is larger than that of the yrast signature partners. However, the measured values are smaller than those predicted by theory. This observation appears to be valid for TSD bands in several nuclei of the region

Candidate superdeformed band in 28Si

Recent antisymmetrized molecular dynamics (AMD) calculations for 28Si suggest the presence of a superdeformed (SD) band with a dominant 24Mg+α clustering for its configuration, with firm predictions for its location and associated moment of inertia. This motivates a review of the experimental results reported in the literature with a particular focus on 24Mg(α,γ) studies, as well as on α-like heavy-ion transfer reactions such as 12C(20Ne,α)28Si. Combining this information for the first time leads to a set of candidate SD states whose properties point to their α-cluster structure and strong associated deformation. Analysis of data from Gammasphere allows the electromagnetic decay of these candidate states to be probed and reveals further supporting evidence for such a structure. This paper appraises this body of information and finds the evidence for an SD band is strong

Configurations and decay hindrances of high- K states in Hf 180

Multi-quasiparticle high-K states, several of which are isomeric, were observed in Hf180 with the Gammasphere array. Lifetimes in the ns-μs range were determined using centroid-shift and decay measurements within a μs coincidence time window. The configurations of high-K states involve two and four quasiparticles, with states up to Kπ=(18-) established. High-K excitations are found to be progressively more favored with increasing excitation energy. The K quantum number is quite robust up to the highest spins observed, as evidenced by the large values of the reduced hindrance for isomeric decays. Rotational bands built on three high-K states are identified, and the measured branching ratios in these sequences enable the assignment of underlying configurations. Multi-quasiparticle calculations using the Lipkin-Nogami approach for pairing, with blocking included, reproduce the observed high-K energies quite well

Reevaluation of the P30(p,γ)S31 astrophysical reaction rate from a study of the T=1/2 mirror nuclei, S31 and P31

The P30(p,γ)S31 reaction rate is expected to be the principal determinant for the endpoint of nucleosynthesis in classical novae. To date, the reaction rate has only been estimated through Hauser-Feschbach calculations and is unmeasured experimentally. This paper aims to remedy this situation. Excited states in S31 and P31 were populated in the C12(Ne20,n) and C12(Ne20,p) reactions, respectively, at a beam energy of 32 MeV, and their resulting γdecay was detected with the Gammasphere array. Around half the relevant proton unbound states in S31 corresponding to the Gamow window for the P30(p,γ)S31 reaction were identified. The properties of the unobserved states were inferred from mirror symmetry using our extended data on P31. The implications of this new spectroscopic information for the P30(p,γ)S31 reaction rate are considered and recommendations for future work with radioactive beams are discussed

T=1 states in Rb74 and their Kr74 analogs

Charge symmetry breaking effects that perturb analog symmetry between nuclei are usually small but are important in extracting reliable Fermi matrix elements from "superallowed" β decays and testing conserved vector current theory, especially for the heavier cases. We have used the Ca40(Ar36, pn)Rb74 and Ca40(Ca40,αpn)Rb74 reactions at 108, 123 and 160 MeV, respectively, to populate Rb74 and determine the analog distortion through comparison of T=1 states in Rb74 with their corresponding Kr74 levels. We have traced the analogs of the Kr74 ground-state band in Rb74 to a candidate spin J=8 state and determined the Coulomb energy differences. They are small and positive and increase smoothly with spin. New T=0 states were found that better delineate the deformed band structure and clarify the steps in deexcitation from high spin. A new T=0 band was found. No evidence was found for γ decay to or from a low-lying Jπ=0+ state in Rb74 despite a careful search

Triple negative breast cancer: proposals for a pragmatic definition and implications for patient management and trial design.

In trials in triple negative breast cancer (TNBC), oestrogen and progesterone receptor negativity should be defined as < 1% positive cells. Negativity is a ratio of <2 between Her2 gene copy number and centromere of chromosome 17 or a copy number of 4 or less. In routine practice, immunohistochemistry is acceptable given stringent quality assurance. Triple negativity emerging after neoadjuvant treatment differs from primary TN and such patients should not enter TNBC trials. Patients relapsing with TN metastases should be eligible even if their primary was positive. Rare TN subtypes such as apocrine, adenoid-cystic and low-grade metaplastic tumours should be excluded. TN and basal-like (BL) signatures overlap but are not equivalent. Since the significance of basal cytokeratin or EGFR overexpression is not known and we lack validated assays, these features should not be used to subclassify TN tumours. Tissue collection in trials is mandatory so the effect on outcome of different tumour phenotypes and BRCA mutation can be explored. No prospective studies have established that TN tumours have particular sensitivity or resistance to any specific chemotherapy agent or radiation. TNBC patients should be treated according to tumour and clinical characteristics