Time-dependent multi-orbital mean-field for fragmented Bose-Einstein condensates

The evolution of Bose-Einstein condensates is usually described by the famous time-dependent Gross-Pitaevskii equation, which assumes all bosons to reside in a single time-dependent orbital. In the present work we address the evolution of fragmented condensates, for which two (or more) orbitals are occupied, and derive a corresponding time-dependent multi-orbital mean-field theory. We call our theory TDMF($n$), where $n$ stands for the number of evolving fragments. Working equations for a general two-body interaction between the bosons are explicitly presented along with an illustrative numerical example.Comment: 16 pages, 1 figur

Thermal seasons in northern Europe in projected future climate

Global warming acts to prolong thermal summers and shorten winters. In this work, future changes in the lengths and timing of four thermal seasons in northern Europe, with threshold temperatures 0 and 10 degrees C, are derived from bias-adjusted output data from 23 CMIP5 global climate models. Three future periods and two Representative Concentration Pathway (RCP) scenarios are discussed. The focus is on the period 2040-2069 under RCP4.5, which approximately corresponds to a 2 degrees C global warming relative to the preindustrial era. By the period 2040-2069, the average length of the thermal summer increases by nearly 30 days relative to 1971-2000, and the thermal winter shortens by 30-60 days. The timing of the thermal springs advances while autumns delay. Within the model ensemble, there is a high linear correlation between the modelled annual-mean temperature increase and shifts in the thermal seasons. Thermal summers lengthen by about 10 days and winters shorten by 10-24 days per 1 degrees C of local warming. In the mid-21st century, about two-thirds of all summers (winters) are projected to be very long (very short) according to the baseline-period standards, with an anomaly greater than 20 days relative to the late-20th century temporal mean. The proportion of years without a thermal winter increases remarkably in the Baltic countries and southern Scandinavian peninsula. Implications of the changing thermal seasons on nature and human society are discussed in a literature review.Peer reviewe

A numerical comparison of theories of violent relaxation

Using N-body simulations with a large set of massless test particles we compare the predictions of two theories of violent relaxation, the well known Lynden-Bell theory and the more recent theory by Nakamura. We derive ``weaken'' versions of both theories in which we use the whole equilibrium coarse-grained distribution function as a constraint instead of the total energy constraint. We use these weaken theories to construct expressions for the conditional probability $K_i(\tau)$ that a test particle initially at the phase-space coordinate $\tau$ would end-up in the $i$'th macro-cell at equilibrium. We show that the logarithm of the ratio $R_{ij}(\tau) \equiv K_i(\tau)/K_j(\tau)$ is directly proportional to the initial phase-space density $f_0(\tau)$ for the Lynden-Bell theory and inversely proportional to $f_0(\tau)$ for the Nakamura theory. We then measure $R_{ij}(\tau)$ using a set of N-body simulations of a system undergoing a gravitational collapse to check the validity of the two theories of violent relaxation. We find that both theories are at odds with the numerical results, qualitatively and quantitatively.Comment: Replaced with a revised version, which is now accepted to MNRAS. LaTeX, 12 pages, 6 figure

Non-stationary Rayleigh-Taylor instability in supernovae ejecta

The Rayleigh-Taylor instability plays an important role in the dynamics of several astronomical objects, in particular, in supernovae (SN) evolution. In this paper we develop an analytical approach to study the stability analysis of spherical expansion of the SN ejecta by using a special transformation in the co-moving coordinate frame. We first study a non-stationary spherical expansion of a gas shell under the pressure of a central source. Then we analyze its stability with respect to a no radial, non spherically symmetric perturbation of the of the shell. We consider the case where the polytropic constant of the SN shell is $\gamma=5/3$ and we examine the evolution of a arbitrary shell perturbation. The dispersion relation is derived. The growth rate of the perturbation is found and its temporal and spatial evolution is discussed. The stability domain depends on the ejecta shell thickness, its acceleration, and the perturbation wavelength.Comment: 16 page

Americans on International Trade Policy

A policymaking simulation is an online process that puts citizens in the shoes of elected officials by simulating the process they go through in making policy decisions. Each simulation introduces a broader policy topic and then presents a series of modules that address a specific policy option that is currently under consideration in the current discourse. For each module, respondents: 1) receive a short briefing on a policy issue and the option or options for addressing it; 2) evaluate arguments for and against the policy options; and 3) finally, make their recommendation for what their elected officials should do.Promoting the Growth of Trade Through an International Rules-Based System: Respondents were introduced to the international system for promoting international trade—two-thirds said they were familiar with it. Evaluating arguments for and against continuing to seek to further the growth of international trade through international agreements, in most cases large majorities from both parties found both pro and con arguments convincing, with Democrats responding more to the pro arguments and Republicans responding more to the con arguments. Nonetheless, in the end an overwhelming bipartisan majority approved of United States, together with other countries, promoting international trade through a set of agreed-on rules that seek to lower barriers to trade and to ensure trade is done fairly. The World Trade Organization: A very large majority approved of the US continuing to be part of the World Trade Organization, though for Republicans this was only a modest majority, while Democrats approved overwhelmingly. MITIGATING THE NEGATIVE EFFECTS OF TRADE: Increasing Unemployment Benefits: As a means of addressing some of the negative effects of trade, a bipartisan majority favored increasing unemployment benefits, with a majority favoring increasing the amount from 39% to 50% of previous earnings. However, a bipartisan majority did not support increasing the maximum period of unemployment benefits beyond the current average of 26 weeks. Worker Retraining and Education: Presented several proposals for job training and education under consideration in Congress, very large bipartisan majorities favored proposals to increase spending on training for jobs in cybersecurity and the energy industry, and a proposal to provide employers a tax credit for apprenticeship programs. Trade Adjustment Assistance: A majority of six in ten favored expanding the Trade Adjustment Assistance program to more people who get laid off from their job directly because of an increase in trade, however six in ten Republicans were opposed. Just four in ten, but a modest majority of Democrats, favored extending such assistance to all people who get laid off from their job. Labor and Environment Standards in Trade Agreements: Overwhelming bipartisan majorities favored including in new international trade agreements the requirement that countries abide by both the labor and environmental standards they have committed to, that they do not lower their standards to attract business or to get a competitive edge, and that there is an effective system for enforcing these requirements. Impact of Mitigating Negative Effects on Attitudes About Trade: Respondents who disapproved of promoting greater trade through international agreements, while also favoring steps to mitigate the negative effects, were asked how they would feel about the promoting trade if the mitigating steps they favored were adopted. About half said that they would then favor promoting greater trade through international agreements. THE USE OF TARIFFS: Steel Tariffs: Voters divided sharply along party lines on the US administration invoking the national security exemption and imposing tariffs of 25% on steel imports and 10% on aluminum imports, with a large majority of Republicans approving and a large majority of Democrats disapproving. Overall, a very slight majority approved. Tariffs on China: Voters divided along party lines on whether the US should have imposed tariffs on China without first getting a WTO ruling. Going forward, a modest majority opposed imposing additional tariffs on China to get them to change their trade practices, but instead favored working through the WTO to get a ruling against China. Views on both issues are highly polarized along partisan lines with large majorities of Democrats favoring working through the WTO and large majorities of Republicans favoring imposing tariffs. North American Trade: NAFTA and the USMCA: Asked about the original North American Free Trade Agreement (NAFTA) agreement, a very large majority, including a majority of Republicans, expressed approval. Told about the proposed U.S.-Mexico-Canada Agreement (USMCA) agreement, a slight majority favored it, with large majority of Republicans in support and a modest majority of Democrats opposed. If Congress does not approve the USMCA deal, a large majority favors staying in NAFTA. Those who favored the new USMCA agreement and approved the steel and aluminum tariffs were asked whether they would be willing to lift the new steel and aluminum tariffs on imports from Canada and Mexico if it appears necessary to get an agreement on USMCA; most said they would

Enhanced inverse bremsstrahlung heating rates in a strong laser field

Test particle studies of electron scattering on ions, in an oscillatory electromagnetic field have shown that standard theoretical assumptions of small angle collisions and phase independent orbits are incorrect for electron trajectories with drift velocities smaller than quiver velocity amplitude. This leads to significant enhancement of the electron energy gain and the inverse bremsstrahlung heating rate in strong laser fields. Nonlinear processes such as Coulomb focusing and correlated collisions of electrons being brought back to the same ion by the oscillatory field are responsible for large angle, head-on scattering processes. The statistical importance of these trajectories has been examined for mono-energetic beam-like, Maxwellian and highly anisotropic electron distribution functions. A new scaling of the inverse bremsstrahlung heating rate with drift velocity and laser intensity is discussed.Comment: 12 pages, 12 figure

Overweight in relation to allergic disease in childhood and adolescence

The prevalences of childhood overweight and allergic diseases have increased in parallel during the last decades. The overall aim of this thesis was to investigate the associations between overweight (maternal and childhood) and allergic diseases, as well as lung function, throughout childhood up to adolescence. In addition, we investigated the validity of self-reported height, weight and corresponding body mass index (BMI) among Swedish adolescents. All studies were based on the BAMSE study, a population-based birth cohort of 4,089 children followed until age 16 years. Maternal BMI was obtained from the Swedish medical birth register, while childhood BMI was measured at clinical investigations, collected from child and school health care records and self-reported. Allergic diseases were assessed by repeated questionnaires regarding symptoms and medications, while allergic sensitization to inhalant allergens was defined by the presence of specific immunoglobulin E (IgE)-antibodies in blood. Lung function was measured by spirometry at 8 and 16 years and by impulse oscillometry (IOS) at 16 years. The results of Study I showed that maternal BMI in early pregnancy was associated with asthma, but not rhinitis, eczema or allergic sensitization in the offspring up to 16 years. The association was strongest for persistent asthma, while no increased risk was observed for transient asthma. Categorization of maternal BMI showed that maternal obesity, but not overweight, was significantly associated with childhood asthma. However, the child’s own weight status could partly explain the observed association between maternal BMI and asthma in the offspring. In Study II, we found that girls with persistent asthma had a higher BMI and an increased risk of overweight throughout childhood, compared to girls without asthma. Girls with transient asthma had an increased risk of overweight at ages 4-7.9 years, whereas girls with late-onset asthma had a tendency towards an increased risk of overweight at age ≥15 years. In boys, the difference in BMI between children with and without asthma was smaller, and no consistent association was observed between asthma phenotypes and overweight. In Study III, we observed that overweight and obesity at age 8 years were associated with increased forced vital capacity (FVC) and to some extent forced expiratory volume in one second (FEV1), but reduced FEV1/FVC ratios at 8 and 16 years. The strongest association with FEV1/FVC was observed for persistent overweight at both 8 and 16 years, whereas no significant association was found for transient overweight. Cross-sectional analyses of IOS showed that overweight and obesity were associated with higher peripheral airway resistance and reactance at 16 years. The result of Study IV showed that self-reported and measured height and weight were highly correlated at 16 years (r=0.98 for height, r=0.96 for weight). On average, self-reported weight was underreported by 1.1 kg and height was overreported by 0.5 cm, leading to an underestimation of BMI by 0.5 kg/m2. The accuracy of self-reported BMI was somewhat lower among girls and among overweight and obese participants, compared to normal weight participants. Our results suggest that maternal and childhood overweight and obesity are associated with asthma and evidence of airway obstruction in children and adolescents. The association between maternal BMI and asthma may, to some extent, be mediated through childhood overweight and seems to be explained by non-allergic mechanisms. In addition, we conclude that web-based self-reported BMI can be used as a valid, quick and cost-effective alternative to measured BMI among Swedish adolescents. The accuracy however declines with increasing BMI, and is somewhat lower among girls compared to boys

Residential greenness is differentially associated with childhood allergic rhinitis and aeroallergen sensitization in seven birth cohorts

Background The prevalence of allergic rhinitis is high, but the role of environmental factors remains unclear. We examined cohort‐specific and combined associations of residential greenness with allergic rhinitis and aeroallergen sensitization based on individual data from Swedish (BAMSE), Australian (MACS), Dutch (PIAMA), Canadian (CAPPS and SAGE), and German (GINIplus and LISAplus) birth cohorts (n = 13 016). Methods Allergic rhinitis (doctor diagnosis/symptoms) and aeroallergen sensitization were assessed in children aged 6–8 years in six cohorts and 10–12 years in five cohorts. Residential greenness was defined as the mean Normalized Difference Vegetation Index (NDVI) in a 500‐m buffer around the home address at the time of health assessment. Cohort‐specific associations per 0.2 unit increase in NDVI were assessed using logistic regression models and combined in a random‐effects meta‐analysis. Results Greenness in a 500‐m buffer was positively associated with allergic rhinitis at 6–8 years in BAMSE (odds ratio = 1.42, 95% confidence interval [1.13, 1.79]) and GINI/LISA South (1.69 [1.19, 2.41]) but inversely associated in GINI/LISA North (0.61 [0.36, 1.01]) and PIAMA (0.67 [0.47, 0.95]). Effect estimates in CAPPS and SAGE were also conflicting but not significant (0.63 [0.32, 1.24] and 1.31 [0.81, 2.12], respectively). All meta‐analyses were nonsignificant. Results were similar for aeroallergen sensitization at 6–8 years and both outcomes at 10–12 years. Stratification by NO2 concentrations, population density, an urban vs rural marker, and moving did not reveal consistent trends within subgroups. Conclusion Although residential greenness appears to be associated with childhood allergic rhinitis and aeroallergen sensitization, the effect direction varies by location

Introduction of oral vitamin D supplementation and the rise of the allergy pandemic

The history of the allergy pandemic is well documented, enabling us to put the vitamin D hypothesis into its historical context. The purpose of this study is to compare the prevalence of rickets, vitamin D supply, and allergy prevalence at 50-year intervals by means of a retrospective analysis of the literature since 1880

Prime movers : mechanochemistry of mitotic kinesins

Mitotic spindles are self-organizing protein machines that harness teams of multiple force generators to drive chromosome segregation. Kinesins are key members of these force-generating teams. Different kinesins walk directionally along dynamic microtubules, anchor, crosslink, align and sort microtubules into polarized bundles, and influence microtubule dynamics by interacting with microtubule tips. The mechanochemical mechanisms of these kinesins are specialized to enable each type to make a specific contribution to spindle self-organization and chromosome segregation