Cryptocurrencies : Threats and Applications from a Monetary Economic Perspective

Over the last years, cryptocurrencies gained attention from all over the world. However, one of the main reasons for their popularity, namely their independence from central banks and politics, might similarly impose severe threats to the financial system. The aim of this paper is to consider cryptocurrencies from a monetary economic standpoint by assessing what sets them apart from fiat money and why they might impose risks on existing financial systems and players. Based on that, we assess their current and potential application in practice by observing their traits as investment object, their ability to act as a safe haven and as a medium of exchange in cross-border trade from a traditional monetary economic point of view. Finally, this paper analyzes whether cryptocurrencies could serve as money in a traditional sense, hurdles they needed to take and potential implications of their implementation. Based on our assessment, their current functioning as currency in a traditional sense is still very limited so far, whereas regulatory forces will closely monitor and attempt to prevent unwanted developments. Consequently, their most promising field of application rather lies in other areas of application, especially in cross-border trade, as their unique characteristic bringing considerable potentials for saving intermediary and exchange costs. However, if States and Central Banks are capable of maintaining and improving all functionalities of fiat money, to keep it transparent, stable and technically up-to-date and to meet the demand of publicity, the desire to hold cryptocurrencies as alternative currencies might become obsolete

Axial Anomaly and Polarized Radiative Decays

We extend the approach of Dolgov and Zakharov to the axial anomaly to study polarized radiative decays. We analyse the pattern of mass singularity cancellation in the corresponding decay rates. We compare polarized and unpolarized cases. The cancellation of the infrared and collinear singularities is verified to all powers of the lepton mass for the $\pi^+$ and $Z^0$ polarized radiative decays.Comment: 18 pages, LaTeX, 4 PostScript figure

Fitbit Charge HR Wireless Heart Rate Monitor: Validation Study Conducted Under Free-Living Conditions

Background: Many modern smart watches and activity trackers feature an optical sensor that estimates the wearer’s heart rate. Recent studies have evaluated the performance of these consumer devices in the laboratory. Objective: The objective of our study was to examine the accuracy and sensitivity of a common wrist-worn tracker device in measuring heart rates and detecting 1-min bouts of moderate to vigorous physical activity (MVPA) under free-living conditions. Methods: Ten healthy volunteers were recruited from a large university in Singapore to participate in a limited field test, followed by a month of continuous data collection. During the field test, each participant would wear one Fitbit Charge HR activity tracker and one Polar H6 heart rate monitor. Fitbit measures were accessed at 1-min intervals, while Polar readings were available for 10-s intervals. We derived intraclass correlation coefficients (ICCs) for individual participants comparing heart rate estimates. We applied Centers for Disease Control and Prevention heart rate zone cut-offs to ascertain the sensitivity and specificity of Fitbit in identifying 1-min epochs falling into MVPA heart rate zone. Results: We collected paired heart rate data for 2509 1-min epochs in 10 individuals under free-living conditions of 3 to 6 hours. The overall ICC comparing 1-min Fitbit measures with average 10-s Polar H6 measures for the same epoch was .83 (95% CI .63-.91). On average, the Fitbit tracker underestimated heart rate measures by −5.96 bpm (standard error, SE=0.18). At the low intensity heart rate zone, the underestimate was smaller at −4.22 bpm (SE=0.15). This underestimate grew to −16.2 bpm (SE=0.74) in the MVPA heart rate zone. Fitbit devices detected 52.9% (192/363) of MVPA heart rate zone epochs correctly. Positive and negative predictive values were 86.1% (192/223) and 92.52% (2115/2286), respectively. During subsequent 1 month of continuous data collection (270 person-days), only 3.9% of 1-min epochs could be categorized as MVPA according to heart rate zones. This measure was affected by decreasing wear time and adherence over the period of follow-up. Conclusions: Under free-living conditions, Fitbit trackers are affected by significant systematic errors. Improvements in tracker accuracy and sensitivity when measuring MVPA are required before they can be considered for use in the context of exercise prescription to promote better health

Cross-Sectional Study of Online Preferences Among Adolescents

Background: The Internet is widely used by adolescents for sexual health information and bears the potential to increase knowledge and positively affect behavior. Objective: The objective of this study is to assess students’ preferences when looking for sexual health information online. Methods: We conducted a cross-sectional survey among ninth grade students in a convenience sample of 13 secondary schools in Berlin, Germany. During a regular school period, participants were requested to rate the importance they attribute to nine aspects of sexual health websites in a paper-based questionnaire. Bivariate and multivariable analyses were used to assess awareness and preferences by gender, age, migrant background, and school type. Results: Of 1190 eligible students, 1177 (98.91%) students with a mean age of 14.6 (SD 0.7) years participated, 52.52% (605/1152) were male, and 52.94% (612/1156) had at least one parent born abroad. Participant numbers were spread equally across three types of secondary schools in Berlin. Website aspects most frequently cited as important were easily comprehensible wording (88.33%, 961/1088), clear information layout (80.57%, 871/1081), and reliability of the website’s publisher (79.28%, 857/1081), whereas the visual style of a website was deemed important by the lowest number of students (35.13%, 378/1076). There was a marked gender difference in the importance students attached to website publisher reliability. Although 437/515 (84.9%) of female participants regarded this as important, only 420/566 (74.2%) of male participants did likewise (P<.001). In multivariable analyses, demographic differences were also particularly visible in the importance of publisher reliability: male participants were significantly less likely to find this aspect important (OR 0.50, 95% CI 0.37-0.69). The odds ratio for students with migrant background was 0.64 (95% CI 0.50-0.81, reference=no migrant background) and OR 2.04 (95% CI 1.03-4.03) for students in the most academic school type (reference=least academic). Conclusions: Students prefer easily understandable online resources. Setting up sexual health websites according to the explicit preferences of the target audience might encourage usage, especially by those subpopulations less likely to critically assess information validity: male adolescents, children of immigrants, and the academically disadvantaged

Renormalons in Effective Field Theories

We investigate the high-order behavior of perturbative matching conditions in effective field theories. These series are typically badly divergent, and are not Borel summable due to infrared and ultraviolet renormalons which introduce ambiguities in defining the sum of the series. We argue that, when treated consistently, there is no physical significance to these ambiguities. Although nonperturbative matrix elements and matching conditions are in general ambiguous, the ambiguity in any physical observable is always higher order in $1/M$ than the theory has been defined. We discuss the implications for the recently noticed infrared renormalon in the pole mass of a heavy quark. We show that a ratio of form factors in exclusive $\Lambda_b$ decays (which is related to the pole mass) is free from renormalon ambiguities regardless of the mass used as the expansion parameter of HQET. The renormalon ambiguities also cancel in inclusive heavy hadron decays. Finally, we demonstrate the cancellation of renormalons in a four-Fermi effective theory obtained by integrating out a heavy colored scalar.Comment: Minor changes mad

Linear polarization sensitivity of SeGA detectors

Parity is a key observable in nuclear spectroscopy. Linear polarization measurements of $\gamma$-rays are a probe to access the parities of energy levels. Utilizing the segmentation of detectors in the Segmented Germanium Array (SeGA) at the NSCL and analyzing the positions of interaction therein allows the detectors to be used as Compton polarimeters. Unlike other segmented detectors, SeGA detectors are irradiated from the side to utilize the transversal segmentation for better Doppler corrections. Sensitivity in such an orientation has previously been untested. A linear polarization sensitivity $Q \approx 0.14$ has been measured in the 350-keV energy range for SeGA detectors using $\alpha$-$\gamma$ correlations from a \nuc{249}{Cf} source.Comment: 7 pages, 9 figure

Eikonal Wave Functions and Model Independent Exclusive B Decays

In this letter we investigate the proper normalization for the B meson eikonal valence wave function used in exclusive B decays. The normalization appropriate for a hard scattering process renormalized at the scale $\mu$ is determined by calculating the short distance contribution to the purely leptonic decay.Comment: 8 pages (3 figures available upon request), UM-TH-94-0

Exploring the Invisible Renormalon: Renormalization of the Heavy-Quark Kinetic Energy

Using the virial theorem of the heavy-quark effective theory, we show that the mixing of the operator for the heavy-quark kinetic energy with the identity operator is forbidden at the one-loop order by Lorentz invariance. This explains why such a mixing was not observed in several one-loop calculations using regularization schemes with a Lorentz-invariant UV regulator, and why no UV renormalon singularity was found in the matrix elements of the kinetic operator in the bubble approximation (the ``invisible renormalon''). On the other hand, we show that the mixing is not protected in general by any symmetry, and it indeed occurs at the two-loop order. This implies that the parameter $\lambda_1^H$ of the heavy-quark effective theory is not directly a physical quantity, but requires a non-perturbative subtraction.Comment: 13 pages, 3 figure

Axial Anomaly Effects in Pion and Z0Z^0 Radiative Decays

We discuss a connection between axial anomaly and polarized radiative processes. By comparison with the corresponding unpolarized cases, we consider some physical outputs for the $\pi^+$ and $Z^0$ polarized radiative decays. We analyse in detail the pattern of mass singularity cancellation.Comment: 30 pages, 7 figure

Theoretical Review of B-physics

Weak decays and mixing of B-hadrons play a special role in our understanding of the physics of the Standard Model and beyond. The measured amplitudes, however, result from a complicated interplay of weak and strong interaction effects. Understanding strong interaction dynamics, which becomes simpler for heavy quarks, is thus a fundamental part of the game. In this review, several theoretical aspects of B dynamics which are relevant for current and future experimental measurements are discussed.Comment: LaTeX, 27 pages, 5 figures. Summary talk given at BEAUTY 96, June 17-21 1996, Rome (Italy), to appear in the Proceeding