Hexagon functions and the three-loop remainder function

We present the three-loop remainder function, which describes the scattering of six gluons in the maximally-helicity-violating configuration in planar N=4 super-Yang-Mills theory, as a function of the three dual conformal cross ratios. The result can be expressed in terms of multiple Goncharov polylogarithms. We also employ a more restricted class of "hexagon functions" which have the correct branch cuts and certain other restrictions on their symbols. We classify all the hexagon functions through transcendental weight five, using the coproduct for their Hopf algebra iteratively, which amounts to a set of first-order differential equations. The three-loop remainder function is a particular weight-six hexagon function, whose symbol was determined previously. The differential equations can be integrated numerically for generic values of the cross ratios, or analytically in certain kinematics limits, including the near-collinear and multi-Regge limits. These limits allow us to impose constraints from the operator product expansion and multi-Regge factorization directly at the function level, and thereby to fix uniquely a set of Riemann-zeta-valued constants that could not be fixed at the level of the symbol. The near-collinear limits agree precisely with recent predictions by Basso, Sever and Vieira based on integrability. The multi-Regge limits agree with the factorization formula of Fadin and Lipatov, and determine three constants entering the impact factor at this order. We plot the three-loop remainder function for various slices of the Euclidean region of positive cross ratios, and compare it to the two-loop one. For large ranges of the cross ratios, the ratio of the three-loop to the two-loop remainder function is relatively constant, and close to -7.Comment: 103 pages, 12 figures, 9 ancillary files. v2: typos corrected, references adde

Be-10 age constraints on latest Pleistocene and Holocene cirque glaciation across the western United States

Paleoclimate: A rocky reworking of Holocene glaciology New dating of glacially-deposited rocks substantially revises our understanding of the waxing and waning of ice since the last glacial maximum. Glaciologists have long thought that moraines throughout the western United States represent ‘neoglacial’ advances about 6,000 years ago. Now, a multi-institution team led by Shaun Marcott at the University of Wisconsin-Madison has found — using cosmogenic isotopes — that these terminal deposits left by advancing glaciers are instead 9,000 to 15,000 years old. The research advances prior work by using absolute, not relative ages, and documents that glaciers retreated after the last glacial maximum ~ 21,000 years ago, fluctuated locally throughout much of the Holocene, and re-advanced during the Little Ice Age of a few hundred years ago. Glacial advances that might have occurred during the neoglacial were wiped away by the more extensive glaciations of the Little Ice Age

Spin Dynamics in the Magnetic Chains Arrays of Sr14Cu24O41: a Neutron Inelastic scattering Investigation

Below about 150 K, the spin arrangement in the chain arrays of Sr14Cu24O41 is shown to develop in two dimensions (2D). Both the correlations and the dispersion of the observed elementary excitations agree well with a model of interacting dimers. Along the chains, the intra- and inter-dimer distances are equal to 2 and about 3 times the distance (c) between neighboring Cu ions. While the intra-dimer coupling is J about 10 meV, the inter-dimer couplings along and between the chains are of comparable strenght, J// about -1.1 meV and Jperp about 1.7 meV, respectively. This remarkable 2D arrangement satisfies the formal Cu valence of the undoped compound. Our data suggest also that it is associated with a relative sliding of one chain with respect to the next one, which, as T decreases, develops in the chain direction. A qualitative analysis shows that nearest inter-dimer spin correlations are ferromagnetic, which, in such a 2D structure, could well result from frustration effects.Comment: 4 pages, 5 figures, submitted to Phys.Rev.B, date of receipt 29 June 199

Modes of Global Climate Variability during Marine Isotope Stage 3 (60–26 ka)

Recent analysis of 38 globally distributed paleoclimatic records covering Marine Isotope Stage 3 (MIS 3) 60–26 ka demonstrated that the two leading empirical orthogonal functions (EOFs) explaining the data are the Greenland ice-core signal (“northern” signal) and the Antarctic ice-core signal (“southern” signal). Here singular spectral analysis (SSA) is used to show that millennial-scale variability of each of these two leading EOFs is characterized by two independent modes. The two modes of each EOF share similar relative distributions of variance, identical spectra, and, where each mode has spectral power, coherency spectra, which are significantly above the null hypothesis level at 95% confidence. The only difference between the modes of the northern and southern signals is that they are phase shifted. The phasing and long response time of the low-frequency mode, combined with its relationship to atmospheric CO2 and sea level, are consistent with coupled changes in the ocean, ice sheets, atmosphere, and carbon cycle, whereas the phasing and short response time of the high-frequency mode are consistent with an atmospheric transmission likely induced by changes in hemispheric sea ice distributions and attendant feedbacks.Keywords: Empirical orthogonal functions, Climate variabilit

Law and the Body in Joseon Korea: Statecraft and the Negotiation of Ideology

Once considered almost exclusively to be the domain of legal scholars, Joseon dynasty criminal law is recently attracting increasing attention from social, political and intellectual historians of Korea. Despite often reaching opposing conclusions on the characteristics of Joseon legal culture, historians and legal scholars share a strong focus on the dominating role of Confucian ideology. While acknowledging the importance of Confucianism for Joseon statecraft, this paper argues that in actual statecraft and the application of the law, this ideology was negotiated with the perceived needs of the state. The focus of analysis is the relationship between the judicial process—investigation, interrogation and punishment—and cosmological, ideological and cultural notions related to the body. The purpose is to show the tension between the state need to maintain the system and uphold social order (as defined by the state) and the need for the state itself to adhere to the basic principles of the ideology that underpinned this system. Addressing the role of law and punishment in statecraft, the analysis is based on a theoretical framework that combines a conflict-based understanding of society with one that is consensus-based. While on the one hand the violation of notions related to the body was the purport of punishment when dealing with the most severe crimes against the state and its ideology, we can also see how such notions influenced the discourses on penal benevolence, torture and exhumation, whilst partly constituting the reason why some forms of torture were prohibited

Geochemical proxies of North American freshwater routing during the Younger Dryas cold event

Author Posting. © The Authors, 2006. This is the author's version of the work. It is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences 104 (2007): 6556-6561, doi:10.1073/pnas.0611313104.The Younger Dryas cold interval represents a time when much of the Northern Hemisphere cooled from ~12.9 to 11.5 kiloyears before present. The cause of this event, which has long been viewed as the canonical example of abrupt climate change, was initially attributed to the routing of freshwater to the St. Lawrence River with an attendant reduction in Atlantic meridional overturning circulation. However, this mechanism has recently been questioned because current proxies and dating techniques have been unable to confirm that eastward routing with an increase in freshwater flux occurred during the Younger Dryas. Here we use new geochemical proxies (ΔMg/Ca, U/Ca & 87Sr/86Sr) measured in planktonic foraminifera at the mouth of the St. Lawrence Estuary as tracers of freshwater sources to further evaluate this question. Our proxies, combined with planktonic δ18Oseawater and δ13C, confirm that routing of runoff from western Canada to the St. Lawrence River occurred at the start of the Younger Dryas, with an attendant increase in freshwater flux of 0.06 ± 0.02 Sverdrup (1 Sverdrup (Sv) = 106 m3 s-1). This base discharge increase is sufficient to have reduced Atlantic meridional overturning circulation and caused the Younger Dryas cold interval. In addition, our data indicate subsequent fluctuations in the freshwater flux to the St. Lawrence River of ~0.06 to 0.12 Sv, thus explaining the variability in the overturning circulation and climate during the Younger Dryas.This research was funded by the NSF Paleoclimate Program (P.U.C.) and the NSF (G.P.K.)

A double-blind placebo controlled trial into the impacts of HMB supplementation and exercise on free-living muscle protein synthesis, muscle mass and function, in older adults

Age-related sarcopenia and dynapenia are associated with frailty and metabolic diseases. Resistance exercise training (RET) adjuvant to evidence-based nutritional intervention(s) have been shown as mitigating strategies. Given that \u3b2-hydroxy-\u3b2-methyl-butyrate (HMB) supplementation during RET improves lean body mass in younger humans, and that we have shown that HMB acutely stimulates muscle protein synthesis (MPS) and inhibits breakdown; we hypothesized that chronic supplementation of HMB free acid (HMB-FA) would enhance MPS and muscle mass/function in response to RET in older people. We recruited 16 healthy older men (Placebo (PLA): 68.5 \ub1 1.0 y, HMB-FA: 67.8 \ub1 1.15 y) for a randomised double-blind-placebo controlled trial (HMB-FA 3 7 1 g/day vs. PLA) involving a 6-week unilateral progressive RET regime (6 7 8 repetitions, 75% 1-RM, 3 \ub7 wk 121). Deuterium oxide (D2O) dosing was performed over the first two weeks (0\u20132 wk) and last two weeks (4\u20136 wk) with bilateral vastus lateralis (VL) biopsies at 0\u20132 and 4\u20136 wk (each time 75 \ub1 2 min after a single bout of resistance exercise (RE)) for quantification of early and later MPS responses and post-RE myogenic gene expression. Thigh lean mass (TLM) was measured by DXA, VL thickness and architecture (fibre length and pennation angle) by ultrasound at 0/3/6 wk, and strength by knee extensor 1-RM testing and MVC by isokinetic dynamometry (approx. every 10 days). RET induced strength increases (1-RM) in the exercised leg of both groups (398 \ub1 22N to 499 \ub1 30N HMB-FA vs. 396 \ub1 29N to 510 \ub1 43N PLA (both P < 0.05)). In addition, maximal voluntary contraction (MVC) also increased (179 \ub1 12 Nm to 203 \ub1 12 Nm HMB-FA vs. 185 \ub1 10 Nm to 217 \ub1 11 Nm PLA (both P < 0.05); with no group differences. VL muscle thickness increased significantly in the exercised leg in both groups, with no group differences. TLM (by DXA) rose to significance only in the HMB-FA group (by 5.8%\u20135734 \ub1 245 g p = 0.015 vs. 3.0% to 5644 \ub1 323 g P = 0.06 in PLA). MPS remained unchanged in the untrained legs (UT) 0\u20132 weeks being 1.06 \ub1 0.08%.d 121 (HMB-FA) and 1.14 \ub1 0.09%.d 121 (PLA), the trained legs (T) exhibited increased MPS in the HMB-FA group only at 0\u20132-weeks (1.39 \ub1 0.10%.d 121, P < 0.05) compared with UT: but was not different at 4\u20136-weeks: 1.26 \ub1 0.05%.d 121. However, there were no significant differences in MPS between the HMB-FA and PLA groups at any given time point and no significant treatment interaction observed. We also observed significant inductions of c-Myc gene expression following each acute RE bout, with no group differences. Further, there were no changes in any other muscle atrophy/hypertrophy or myogenic transcription factor genes we measured. RET with adjuvant HMB-FA supplements in free-living healthy older men did not enhance muscle strength or mass greater than that of RET alone (PLA). That said, only HMB-FA increased TLM, supported by early increases in chronic MPS. As such, chronic HMB-FA supplementation may result in long term benefits in older males, however longer and larger studies may be needed to fully determine the potential effects of HMB-FA supplementation; translating to any functional benefit

The Physics of Heavy Flavours at SuperB

This is a review of the SuperB project, covering the accelerator, detector, and highlights of the broad physics programme. SuperB is a flavour factory capable of performing precision measurements and searches for rare and forbidden decays of $B_{u,d,s}$, $D$, $\tau$ and $\Upsilon({\mathrm{nS}})$ particles. These results can be used to test fundamental symmetries and expectations of the Standard Model, and to constrain many different hypothesised types of new physics. In some cases these measurements can be used to place constraints on the existence of light dark matter and light Higgs particles with masses below $10GeV/c^2$. The potential impact of the measurements that will be made by SuperB on the field of high energy physics is also discussed in the context of data taken at both high energy in the region around the \Upsilon({\mathrm{4S}})$, and near charm threshold.Comment: 49 pages, topical review submitted to J. Phys

Rapid Holocene Deglaciation of the Labrador Sector of the Laurentide Ice Sheet

Retreat of the Laurentide Ice Sheet (LIS) following the Last Glacial Maximum 21 000 yr BP affected regional to global climate and accounted for the largest proportion of sea level rise. Although the late Pleistocene LIS retreat chronology is relatively well constrained, its Holocene chronology remains poorly dated, limiting our understanding of its role in Holocene climate change and sea level rise. Here new ¹⁰Be cosmogenic exposure ages on glacially deposited boulders are used to date the final disappearance of the Labrador sector of the LIS (LS-LIS). These data suggest that following the deglaciation of the southeastern Hudson Bay coastline at 8.0 ± 0.2 cal ka BP, the southwestern margin of the LS-LIS rapidly retreated ~600 km in 140 yr and most likely in ~600 yr at a rate of ~900 m yr⁻¹, with final deglaciation by 6.8 ± 0.2 ¹⁰Be ka. The disappearance of the LS-LIS ~6.8 ¹⁰Be ka and attendant reduction in freshwater runoff may have induced the formation of Labrador Deep Seawater, while the loss of the high albedo surface may have initiated the Holocene Thermal Maximum in eastern Canada and southern Greenland. Moreover, the rapid melting just prior to ~6.8 ¹⁰Be ka indicates that the remnant LIS may be the primary source of a postulated rapid rise in global sea level of ~5 m that occurred sometime between 7.6 and 6.5 cal ka BP.Keywords: Ice sheets, Glaciers, Climate change, Sea level, AlbedoKeywords: Ice sheets, Glaciers, Climate change, Sea level, Albed