Defect energy of infinite-component vector spin glasses

We compute numerically the zero temperature defect energy, Delta E, of the vector spin glass in the limit of an infinite number of spin components m, for a range of dimensions 2 <= d <= 5. Fitting to Delta E ~ L^theta, where L is the system size, we obtain: theta = -1.54 (d=2), theta = -1.04 (d=3), theta = -0.67 (d=4) and theta = -0.37 (d=5). These results show that the lower critical dimension, d_l (the dimension where theta changes sign), is significantly higher for m=infinity than for finite m (where 2 < d_l < 3).Comment: 4 pages, 5 figure

A molecular and morphological investigation of the red seaweed genus Porphyra (Bangiales, Rhodophyta) in the northwest Atlantic

To evaluate the possible occurrence of cryptic Porphyra taxa in the Northwest Atlantic, extensive field collections were made during winter and spring periods when relatively few previous collections had been made. Approximately 100 different sites extending from Chance Harbor, New Brunswick, Canada to Rye, New York, USA, were sampled during multiple years (2001-2005). Historical specimens from several herbaria (NHA, FH, BM, WTU, MICH, US) were also examined for possible cryptic taxa. A combination of morphological and molecular tools was used to screen both recent and historical collections. Sequences from the plastid-encoded, ribulose-1, 5-bisphosphate carboxylase-oxygenase large subunit (rbcL) gene and rbcL- rbcS spacer, the nuclear ribosomal small subunit (SSU), and internal transcribed spacer 1 (ITS1) regions were compared with other Porphyra taxa sequences available on GenBank. Sequences from four taxa were found to match Pacific taxa, with three of these having not been previously reported for the Northwest Atlantic (i.e. P. rediviva Stiller & Waaland, P. yezoensis f. narawaensis Miura, P. katadae Miura). In addition, five previously undescribed taxa, with unique rbcL, SSU, and ITS1 sequences were discovered. Porphyra rediviva, which was previously described from the Pacific, could not be morphologically or ecologically distinguished from P. purpurea (Roth) C. Agardh. Additionally, the rbcL and ITS1 sequences from the nomenclatural type specimens of both species were identical, providing compelling evidence for the synonymization of P. rediviva under the older named taxon, P. purpurea. As there was an equal amount of molecular variation within both the Atlantic and Pacific populations of P. purpurea, the designation of a parent population was unclear. With this synonym, the number of known monostromatic species occurring in the Northwest Atlantic having male/female gametangia on separate longitudinal halves of the blade includes P. purpurea, P. birdiae, and P. katadae. While molecular differences among these three species are distinct, morphological and ecological features are less clear. However, differences between these taxa are more apparent if combinations of both morphological and ecological characteristics are used. For example, by combining blade thickness and color, P. katadae can be delineated from both P. purpurea and P. birdiae , while a comparison of distributional patterns show a clear distinction between more northern P. birdiae and southern P. katadae. Despite the recent report of Porphyra yezoensis f. yezoensis from a single site in New Hampshire, USA, molecular screenings of specimens from across the region provides strong evidence of a once continuous distribution from mid-Maine to western Long Island Sound. In addition to the populations of P. yezoensis f. yezoensis in New England, three populations of this taxon were found on the Gulf Coast of Texas, with one specimen dating back to the late 1960\u27s. When comparisons of ITS1 sequences were made with Asian individuals, all New England specimens plus one Texas specimen had identical sequences to Japanese specimens, while the other two Texas populations showed a closer affinity to Chinese populations. Thus, the molecular evidence supports at least two introductions of P. yezoensis f. yezoensis to the Gulf Coast of Texas. The discovery of a second Asiatic cultivar, P. yezoensis f. narawaensis, in New England appears to be of more recent introduction than the established f. yezoensis as documented by its later development (1980\u27s) and more circumscribed distribution that interrupts the continuous distribution of P. yezoensis f. yezoensis. The ITS1 sequences of New England Porphyra yezoensis f. narawaensis populations show no variation and they are identical to as many as 16 commercial strains in Japan. Similarly, the distribution of another Asiatic species discovered in New England, P. katadae, is circumscribed, and it appears to be a recent introduction that shows no sequence variation in either the rbcL gene or ITS1 region. Comparison of ITS1 sequences with Asiatic specimens show New England specimens of P. katadae are identical to a specimen from China and differ by a 1 bp substitution from a specimen from Japan. Four of the five newly discovered taxa are herein described as new species (P. collinsii sp. nov., P. stamfordensis sp. nov., P. tsengii sp. nov., and P. spatuala sp. nov.). Detailed morphological and ecological descriptions are given along with their distributional pattern in New England. Sequences for partial rbcL, rbcL- rbcS spacer, SSU, and ITS1 are submitted to GenBank for type specimens. The fifth new species also occurs in the Mediterranean and has been recently described (as Porphyra olivii sp. nov.) in a joint publication with several European collaborators

Persistence in an antiferromagnetic Ising model with conserved magnetisation

We obtain the persistence exponents for an antiferromagnetic Ising system in which the magnetisation is kept constant. This system belongs to Model C (system with non-conserved order parameter with a conserved density) and is expected to have persistence exponents different from that of Model A (system with no conservation) but independent of the conserved density. Our numerical results for both local persistence at zero temperature and global persistence at the critical temperature however indicate that the exponents are dependent on the conserved magnetisation in both two and three dimensions. This nonuniversal feature is attributed to the presence of the conserved field and is special to the persistence phenomena.Comment: 8 pages, to be published in Physica A (Proceedings of the Statphys-Kolkata IV, 2002

Spin glasses in the limit of an infinite number of spin components

We consider the spin glass model in which the number of spin components, m, is infinite. In the formulation of the problem appropriate for numerical calculations proposed by several authors, we show that the order parameter defined by the long-distance limit of the correlation functions is actually zero and there is only "quasi long range order" below the transition temperature. We also show that the spin glass transition temperature is zero in three dimensions.Comment: 9 pages, 13 figure

Editorial

published_or_final_versionSpringer Open Choice, 01 Dec 201

Persistence in systems with algebraic interaction

Persistence in coarsening 1D spin systems with a power law interaction $r^{-1-\sigma}$ is considered. Numerical studies indicate that for sufficiently large values of the interaction exponent $\sigma$ ($\sigma\geq 1/2$ in our simulations), persistence decays as an algebraic function of the length scale $L$, $P(L)\sim L^{-\theta}$. The Persistence exponent $\theta$ is found to be independent on the force exponent $\sigma$ and close to its value for the extremal ($\sigma \to \infty$) model, $\bar\theta=0.17507588...$. For smaller values of the force exponent ($\sigma< 1/2$), finite size effects prevent the system from reaching the asymptotic regime. Scaling arguments suggest that in order to avoid significant boundary effects for small $\sigma$, the system size should grow as ${[{\cal O}(1/\sigma)]}^{1/\sigma}$.Comment: 4 pages 4 figure

On a Penrose Inequality with Charge

We construct a time-symmetric asymptotically flat initial data set to the Einstein-Maxwell Equations which satisfies the inequality: m - 1/2(R + Q^2/R) < 0, where m is the total mass, R=sqrt(A/4) is the area radius of the outermost horizon and Q is the total charge. This yields a counter-example to a natural extension of the Penrose Inequality to charged black holes.Comment: Minor revision: some typos; author's address updated; bibliographical reference added; journal information: to appear in Comm. Math. Phy

Analysis of prehistoric brown earth paleosols under the podzol soils of Exmoor, UK

The deforestation of the upland landscapes in southwest Britain during prehistory is an established archaeological narrative, documenting human impacts on the environment and questioning the relationship of prehistoric societies to the upland landscapes they inhabited. Allied to the paleoenvironmental analyses of pollen sequences, which have provided the evidence of this change, there has been some investigation of prehistoric paleosols fossilized under principally Bronze Age archaeological monuments. These analyses identified brown earth soils that were originally associated with temperate deciduous woodland, on occasion showing evidence of human impacts such as tilling. However, the number of analyses of these paleosols has been limited. This study presents the first analysis of a series of pre‐podzol brown earth paleosols on Exmoor, UK, two of which are associated with colluvial soil erosion sediments before the formation of peat. This study indicates these paleosols are spatially extensive and have considerable potential to inform a more nuanced understanding of prehistoric human impacts on the upland environments of the early‐mid Holocene and assess human agency in driving ecosystem change

Effectiveness of a six-week high-intensity interval training programme on cardiometabolic markers in sedentary males

High-intensity interval training (HIT) has been proposed as an effective, time efficient strategy to elicit similar cardiometabolic health benefits as traditional moderate-intensity endurance training. This is an important consideration as "lack of time" is a common cited barrier to regular physical activity