Invariance of the relativistic one-particle distribution function

The one-particle distribution function is of importance both in non-relativistic and relativistic statistical physics. In the relativistic framework, Lorentz invariance is possibly its most fundamental property. The present article on the subject is a contrastive one: we review, discuss critically, and, when necessary, complete, the treatments found in the standard literature

Do dietary patterns in older men influence change in homocysteine through folate fortification? The Normative Aging Study

Objective We aimed to describe the difference in B-vitamin intake and in plasma B-vitamin and homocysteine concentrations before and after folic acid fortification, in relation to dietary patterns. Design The Normative Aging Study (NAS) is a longitudinal study on ageing. Between 1961 and 1970, 2280 male volunteers aged 21¿80 years (mean 42 years) were recruited. Dietary intake data have been collected since 1987 and assessment of plasma B vitamins and homocysteine was added in 1993. Setting Boston, Massachusetts, USA. Subjects In the present study, 354 men who had completed at least one FFQ and one measurement of homocysteine, both before and after the fortification period, were included. Results Three dietary patterns were identified by cluster analysis: (i) a prudent pattern, with relatively high intakes of fruit, vegetables, low-fat milk and breakfast cereals; (ii) an unhealthy pattern, with high intakes of baked products, sweets and added fats; and (iii) a low fruit and vegetable but relatively high alcohol intake pattern. Dietary intake and plasma concentrations of folate increased significantly (P <0·05) among all dietary patterns after the fortification period. Homocysteine tended to decrease in supplement non-users and in subjects in the high alcohol, low fruit and vegetable dietary pattern (both P = 0·08). Conclusions After fortification with folic acid, folate intake and plasma folate concentration increased significantly in all dietary patterns. There was a trend towards greatest homocysteine lowering in the high alcohol, low fruit and vegetable grou

The Cross-Section of Stock Returns in Frontier Emerging Markets

We are the first to investigate the cross-section of stock returns in the new emerging equity markets, the so-called frontier emerging markets. Our unique survivorship-bias free data set consists of more than 1,400 stocks over the period 1997 to 2008 and covers 24 of the most liquid frontier emerging markets. The major benefit of using individual stock characteristics is that it allows us to investigate whether return factors that have been documented in developed countries also exist in these markets. We document the presence of economically and statistically significant value and momentum effects, and a local size effect. Our results indicate that the value and momentum effects still exist when incorporating conservative assumptions of transaction costs. Additionally, we show that value, momentum, and local size returns in frontier markets cannot be explained by global risk factors

Another look at trading costs and short-term reversal profits

Several studies report that abnormal returns associated with short-term reversal investment strategies diminish once trading costs are taken into account. We show that the impact of trading costs on the strategies' profitability can largely be attributed to excessively trading in small cap stocks. Limiting the stock universe to large cap stocks significantly reduces trading costs. Applying a more sophisticated portfolio construction algorithm to lower turnover reduces trading costs even further. Our finding that reversal strategies generate 30-50 basis points per week net of trading costs poses a serious challenge to standard rational asset pricing models. Our findings also have important implications for the understanding and practical implementation of reversal strategies

Assessing Asset Pricing Anomalies

One of the most important challenges in the field of asset pricing is to understand anomalies: empirical patterns in asset returns that cannot be explained by standard asset pricing models. Currently, there is no consensus in the academic literature on the underlying causes of well-known anomalies, such as the value and momentum anomalies. Anomalies could be the result of data mining, disappear when trading costs are taken into account, be a compensation for a particular form of risk, or have a behavioral explanation. The motivation of this research project is to gain more and better insight into possible explanations for well-known asset pricing anomalies. Understanding asset pricing anomalies is of the utmost importance for investors. It allows them to make better informed investment decisions, and thereby achieve higher return premiums. The first study in this dissertation shows that the value, momentum and size anomalies are also present in the new emerging equity markets, the so-called frontier emerging markets, which makes data mining as an explanation for these anomalies unlikely. The second study focuses on trading costs as a possible explanation for the short-term reversal anomaly. Focusing on large-cap stocks and applying a more sophisticated portfolio construction algorithm lower trading costs significantly, such that reversal strategies generate profitable results net of trading costs. The third study examines risk as an explanation for the value and size anomalies. Although value and small-cap exposures are typically associated with distress risk, the results indicate that distress risk is not priced and that the small-cap and value premiums are priced beyond distress risk. The fourth and last study examines a behavioral explanation for the low-risk anomaly. Based on a general equilibrium model, tournament behavior causes the returns of low-risk (high-risk) assets to be larger (smaller) than expected according to the Capital Asset Pricing Model. In addition, empirical analyses confirm a positive and significant relation between tournament behavior and the low-risk premium

1s2p resonant inelastic x-ray scattering in a-Fe2O3

We report experimental and theoretical results on the Fe K edge x-ray absorption spectrum and 1s2p resonant inelastic x-ray scattering (RIXS) spectra in a-Fe2O3 . The results are interpreted using an FeO6^9- cluster model with intra-atomic multiplet coupling and interatomic covalency hybridization. The 1s2p RIXS is treated as a coherent second-order optical process. It is shown that the double-peak structure in the pre-edge region of Fe K absorption spectrum is due to the cubic crystal-field splitting, and that the intensity of the eg (t2g) component in the 1s2p resonant inelastic spectrum is enhanced by tuning the incident photon energy to the eg (t2g) component in the absorption spectrum

Validation of dietary history method in a group of elderly women using measurements of total energy expenditure.

The objective of the present study was to validate energy intake data, obtained by dietary history, in twelve elderly women aged 69–82 years. Energy and protein intakes were obtained using the dietary history method with a reference period of 30 d. Reported energy intake was compared with total energy expenditure (TEE) measured on two consecutive days in a respiration chamber. Reported protein intake was compared with mean N excretion from four 24 h urine collections. Mean reported energy intake was 7.2 (SD 1.5) MJ/d which was lower than TEE (P=0.059). Reported protein intake was 64 (SD 13) g/d and lower than estimated protein intake (P=0.053). The percentage underestimation was not related to body weight or percentage body fat. Subjects with a relatively high TEE or a relatively high estimated protein intake underestimated their energy intake to a greater extent. The discrepancy between reported energy intake and TEE was positively associated with the discrepancy between reported and estimated protein intakes. The results of this present study show an underestimation of energy intake of about 12% when using the dietary history method. Physical activity diaries completed in the chamber and during 4 d at home, as well as pedometer counts, indicated a higher level of physical activity in the free-living situation compared with the chamber situation. This suggests that the actual underestimation of energy intake may be even higher in this group of elderly women. These results have implications for the use of the dietary history method in, for example, epidemiological studies carried out in elderly subjects

Anomalies on orbifolds with gauge symmetry breaking

We embed two 4D chiral multiplets of opposite representations in the 5D N=2 $SU(N+K)$ gauge theory compactified on an orbifold $S^1/(Z_2\times Z'_2)$. There are two types of orbifold boundary conditions in the extra dimension to obtain the 4D N=1 $SU(N)\times SU(K)\times U(1)$ gauge theory from the bulk: in Type I, one has the bulk gauge group at $y=0$ and the unbroken gauge group at $y=\pi R/2$ while in Type II, one has the unbroken gauge group at both fixed points. In both types of orbifold boundary conditions, we consider the zero mode(s) as coming from a bulk $(K+N)$-plet and brane fields at the fixed point(s) with the unbroken gauge group. We check the consistency of this embedding of fields by the localized anomalies and the localized FI terms. We show that the localized anomalies in Type I are cancelled exactly by the introduction of a bulk Chern-Simons term. On the other hand, in some class of Type II, the Chern-Simons term is not enough to cancel all localized anomalies even if they are globally vanishing. We also find that for the consistent embedding of brane fields, there appear only the localized log FI terms at the fixed point(s) with a U(1) factor.Comment: LaTeX file of 19 pages with no figure, published versio

Localized anomalies in orbifold gauge theories

We apply the path-integral formalism to compute the anomalies in general orbifold gauge theories (including possible non-trivial Scherk-Schwarz boundary conditions) where a gauge group G is broken down to subgroups H_f at the fixed points y=y_f. Bulk and localized anomalies, proportional to \delta(y-y_f), do generically appear from matter propagating in the bulk. The anomaly zero-mode that survives in the four-dimensional effective theory should be canceled by localized fermions (except possibly for mixed U(1) anomalies). We examine in detail the possibility of canceling localized anomalies by the Green-Schwarz mechanism involving two- and four-forms in the bulk. The four-form can only cancel anomalies which do not survive in the 4D effective theory: they are called globally vanishing anomalies. The two-form may cancel a specific class of mixed U(1) anomalies. Only if these anomalies are present in the 4D theory this mechanism spontaneously breaks the U(1) symmetry. The examples of five and six-dimensional Z_N orbifolds are considered in great detail. In five dimensions the Green-Schwarz four-form has no physical degrees of freedom and is equivalent to canceling anomalies by a Chern-Simons term. In all other cases, the Green-Schwarz forms have some physical degrees of freedom and leave some non-renormalizable interactions in the low energy effective theory. In general, localized anomaly cancellation imposes strong constraints on model building.Comment: 30 pages, 4 figures. v2: reference adde

On the nature of the so-called generic instabilities in dissipative relativistic hydrodynamics

It is shown that the so-called generic instabilities that appear in the framework of relativistic linear irreversible thermodynamics, describing the fluctuations of a simple fluid close to equilibrium, arise due to the coupling of heat with hydrodynamic acceleration which appears in Eckart's formalism of relativistic irreversible thermodynamics. Further, we emphasize that such behavior should be interpreted as a contradiction to the postulates of linear irreversible thermodynamics (LIT), namely a violation of Onsager's hypothesis on the regression of fluctuations, and not as fluid instabilities. Such contradictions can be avoided within a relativistic linear framework if a Meixner-like approach to the phenomenological equations is employed.Comment: 13 pages, no figures. Accepted for publication in GR