The Quantum Mechanical Arrows of Time

The familiar textbook quantum mechanics of laboratory measurements incorporates a quantum mechanical arrow of time --- the direction in time in which state vector reduction operates. This arrow is usually assumed to coincide with the direction of the thermodynamic arrow of the quasiclassical realm of everyday experience. But in the more general context of cosmology we seek an explanation of all observed arrows, and the relations between them, in terms of the conditions that specify our particular universe. This paper investigates quantum mechanical and thermodynamic arrows in a time-neutral formulation of quantum mechanics for a number of model cosmologies in fixed background spacetimes. We find that a general universe may not have well defined arrows of either kind. When arrows are emergent they need not point in the same direction over the whole of spacetime. Rather they may be local, pointing in different directions in different spacetime regions. Local arrows can therefore be consistent with global time symmetry.Comment: 9 pages, 4 figures, revtex4, typos correcte

Cross-sectional DXA and MR measures of tibial periarticular bone associate with radiographic knee osteoarthritis severity

SummaryObjectiveWe evaluated the relationship of medial proximal tibial periarticular areal bone mineral density (paBMD) and trabecular morphometry and determined whether these bone measures differed across radiographic medial joint space narrowing (JSN) scores.Methods482 participants of the Osteoarthritis Initiative (OAI) Bone Ancillary Study had knee dual X-ray absorptiometry (DXA) and trabecular bone 3T magnetic resonance imaging (MRI) exams assessed at the same visit. Medial proximal tibial paBMD was measured on DXA and apparent trabecular bone volume fraction (aBV/TV), thickness (aTb.Th), number (aTb.N), and spacing (aTb.Sp) were determined from MR images. Radiographs were assessed for medial JSN scores (0–3). We evaluated associations between medial paBMD and trabecular morphometry. Whisker plots with notches of these measures versus medial JSN scores were generated and presented.ResultsMean age was 63.9 (9.2) years, BMI 29.6 (4.8) kg/m2, and 53% were male. The Spearman correlation coefficients between DXA-measured medial paBMD and aBV/TV was 0.61 [95% confidence interval (CI) 0.55–0.66]; between paBMD and aTb.Th was 0.38 (95%CI 0.30–0.46); paBMD and aTb.N was 0.65 (95%CI 0.60–0.70); paBMD and aTb.Sp was −0.65 (95%CI −0.70 to −0.59). paBMD and the trabecular metrics were associated with medial JSN scores.ConclusionThe moderate associations between periarticular trabecular bone density and morphometry and their relationship with greater severity of knee OA support hypotheses of remodeling and/or microscopic compression fractures in the natural history of OA. Longitudinal studies are needed to assess whether knee DXA will be a predictor of OA progression. Further characterization of the periarticular bone in OA utilizing complementary imaging modalities will help clarify OA pathophysiology

Finite-Dimensional Bicomplex Hilbert Spaces

This paper is a detailed study of finite-dimensional modules defined on bicomplex numbers. A number of results are proved on bicomplex square matrices, linear operators, orthogonal bases, self-adjoint operators and Hilbert spaces, including the spectral decomposition theorem. Applications to concepts relevant to quantum mechanics, like the evolution operator, are pointed out.Comment: 21 page

Layer dynamics of a freely standing smectic-A film

We study the hydrodynamics of a freely-standing smectic-A film in the isothermal, incompressible limit theoretically by analyzing the linearized hydrodynamic equations of motion with proper boundary conditions. The dynamic properties for the system can be obtained from the response functions for the free surfaces. Permeation is included and its importance near the free surfaces is discussed. The hydrodynamic mode structure for the dynamics of the system is compared with that of bulk systems. We show that to describe the dynamic correlation functions for the system, in general, it is necessary to consider the smectic layer displacement $u$ and the velocity normal to the layers, $v_z$, together. Finally, our analysis also provides a basis for the theoretical study of the off-equilibrium dynamics of freely-standing smectic-A films.Comment: 22 pages, 4 figure

Comparison of K+K^+ and e−e^- Quasielastic Scattering

We formulate $K^+$-nucleus quasielastic scattering in a manner which closely parallels standard treatments of $e^-$-nucleus quasielastic scattering. For $K^+$ scattering, new responses involving scalar contributions appear in addition to the Coulomb (or longitudinal) and transverse $(e,e')$ responses which are of vector character. We compute these responses using both nuclear matter and finite nucleus versions of the Relativistic Hartree Approximation to Quantum Hadrodynamics including RPA correlations. Overall agreement with measured $(e,e')$ responses and new $K^+$ quasielastic scattering data for $^{40}$Ca at |\qs|=500 MeV/c is good. Strong RPA quenching is essential for agreement with the Coulomb response. This quenching is notably less for the $K^+$ cross section even though the new scalar contributions are even more strongly quenched than the vector contributions. We show that this ``differential quenching'' alters sensitive cancellations in the expression for the $K^+$ cross section so that it is reduced much less than the individual responses. We emphasize the role of the purely relativistic distinction between vector and scalar contributions in obtaining an accurate and consistent description of the $(e,e')$ and $K^+$ data within the framework of our nuclear structure model.Comment: 26 pages, 5 uuencoded figures appended to end of this fil

LexMAL: A quick and reliable lexical test for Malay speakers

Objective language proficiency measures have been found to provide better and more consistent estimates of bilinguals’ language processing than self-rated proficiency (e.g., Tomoschuk et al., 2019; Wen & van Heuven, 2017a). However, objectively measuring language proficiency is often not possible because of a lack of quick and freely available language proficiency tests (Park et al., 2022). Therefore, quick valid vocabulary tests, such as LexTALE (Lemhöfer & Broersma, 2012) and its extensions (e.g., LexITA: Amenta et al., 2020; LEXTALE-FR: Brysbaert, 2013; LexPT: Zhou & Li, 2022) have been developed to reliably assess language proficiency of speakers of various languages. The present study introduces a Lexical Test for Malay Speakers (LexMAL), which estimates language proficiency for Malay first language (L1) and second language (L2) speakers. An initial 180-item LexMAL prototype was evaluated using 60 Malay L1 and 60 L2 speakers in Experiment 1. Sixty words and 30 nonwords with the highest discriminative power that span across the full difficulty range were selected for the final LexMAL based on point-biserial correlations and an item response theory analysis. The validity of LexMAL was demonstrated through a reliable discrimination between L1 and L2 speakers, significant correlations between LexMAL scores and performance on other Malay language tasks (i.e., translation accuracy and cloze test scores), and LexMAL outperforming self-rated proficiency. A validation study (Experiment 2) with the 90-item final LexMAL tested with a different group of Malay L1 (N = 61) and L2 speakers (N = 61) replicated the findings of Experiment 1. LexMAL is freely available for researchers at www.lexmal.org

Spin, charge and orbital ordering in ferrimagnetic insulator YBaMn2_2O5_5

The oxygen-deficient (double) perovskite YBaMn$_2$O$_5$, containing corner-linked MnO$_5$ square pyramids, is found to exhibit ferrimagnetic ordering in its ground state. In the present work we report generalized-gradient-corrected, relativistic first-principles full-potential density-functional calculations performed on YBaMn$_2$O$_5$ in the nonmagnetic, ferromagnetic and ferrimagnetic states. The charge, orbital and spin orderings are explained with site-, angular momentum- and orbital-projected density of states, charge-density plots, electronic structure and total energy studies. YBaMn$_2$O$_5$ is found to stabilize in a G-type ferrimagnetic state in accordance with experimental results. The experimentally observed insulating behavior appears only when we include ferrimagnetic ordering in our calculation. We observed significant optical anisotropy in this material originating from the combined effect of ferrimagnetic ordering and crystal field splitting. In order to gain knowledge about the presence of different valence states for Mn in YBaMn$_2$O$_5$ we have calculated $K$-edge x-ray absorption near-edge spectra for the Mn and O atoms. The presence of the different valence states for Mn is clearly established from the x-ray absorption near-edge spectra, hyperfine field parameters and the magnetic properties study. Among the experimentally proposed structures, the recently reported description based on $P$4/$nmm$ is found to represent the stable structure

Non Linear Current Response of a Many-Level Tunneling System: Higher Harmonics Generation

The fully nonlinear response of a many-level tunneling system to a strong alternating field of high frequency $\omega$ is studied in terms of the Schwinger-Keldysh nonequilibrium Green functions. The nonlinear time dependent tunneling current $I(t)$ is calculated exactly and its resonance structure is elucidated. In particular, it is shown that under certain reasonable conditions on the physical parameters, the Fourier component $I_{n}$ is sharply peaked at $n=\frac {\Delta E} {\hbar \omega}$, where $\Delta E$ is the spacing between two levels. This frequency multiplication results from the highly nonlinear process of $n$ photon absorption (or emission) by the tunneling system. It is also conjectured that this effect (which so far is studied mainly in the context of nonlinear optics) might be experimentally feasible.Comment: 28 pages, LaTex, 7 figures are available upon request from [email protected], submitted to Phys.Rev.

Full adoption of the most effective strategies to mitigate methane emissions by ruminants can help meet the 1.5 °C target by 2030 but not 2050

To meet the 1.5 °C target, methane (CH) from ruminants must be reduced by 11 to 30% by 2030 and 24 to 47% by 2050 compared to 2010 levels. A meta-analysis identified strategies to decrease product-based (PB; CH per unit meat or milk) and absolute (ABS) enteric CH emissions while maintaining or increasing animal productivity (AP; weight gain or milk yield). Next, the potential of different adoption rates of one PB or one ABS strategy to contribute to the 1.5 °C target was estimated. The database included findings from 430 peer-reviewed studies, which reported 98 mitigation strategies that can be classified into three categories: animal and feed management, diet formulation, and rumen manipulation. A random-effects meta-analysis weighted by inverse variance was carried out. Three PB strategies—namely, increasing feeding level, decreasing grass maturity, and decreasing dietary forage-to-concentrate ratio—decreased CH per unit meat or milk by on average 12% and increased AP by a median of 17%. Five ABS strategies—namely CH inhibitors, tanniferous forages, electron sinks, oils and fats, and oilseeds—decreased daily methane by on average 21%. Globally, only 100% adoption of the most effective PB and ABS strategies can meet the 1.5 °C target by 2030 but not 2050, because mitigation effects are offset by projected increases in CH due to increasing milk and meat demand. Notably, by 2030 and 2050, low- and middle-income countries may not meet their contribution to the 1.5 °C target for this same reason, whereas high-income countries could meet their contributions due to only a minor projected increase in enteric CH emissions.We thank the GLOBAL NETWORK project for generating part of the database. The GLOBAL NETWORK project (https://globalresearchalliance.org/research/livestock/collaborative-activities/global-research-project/; accessed 20 June 2020) was a multinational initiative funded by the Joint Programming Initiative on Food Security, Agriculture, and Climate Change and was coordinated by the Feed and Nutrition Network (https://globalresearchalliance.org/research/livestock/networks/feed-nutrition-network/; accessed 20 June 2020) within the Livestock Research Group of the Global Research Alliance on Agricultural GHG (https://globalresearchalliance.org; accessed 20 June 2020). We thank MitiGate, which was part of the Animal Change project funded by the EU under Grant Agreement FP7-266018 for sharing their database with us (http://mitigate.ibers.aber.ac.uk/, accessed 1 July 2017). Part of C.A., A.N.H., and S.C.M.’s time in the early stages of this project was funded by the Kravis Scientific Research Fund (New York) and a gift from Sue and Steve Mandel to the Environmental Defense Fund. Another part of C.A.’s work on this project was supported by the National Program for Scientific Research and Advanced Studies - PROCIENCIA within the framework of the "Project for the Improvement and Expansion of the Services of the National System of Science, Technology and Technological Innovation" (Contract No. 016-2019) and by the German Federal Ministry for Economic Cooperation and Development (issued through Deutsche Gesellschaft für Internationale Zusammenarbei) through the research “Programme of Climate Smart Livestock” (Programme 2017.0119.2). Part of A.N.H.’s work was funded by the US Department of Agriculture (Washington, DC) National Institute of Food and Agriculture Federal Appropriations under Project PEN 04539 and Accession no. 1000803. E.K. was supported by the Sesnon Endowed Chair Fund of the University of California, Davis