Comment on "Melting of Isolated Tin Nanoparticles"

Comment on the paper of T.Bachels, H. J. G\"{u}ntherodt and R.Sch\"{a}fer : "Melting of Isolated Tin Nanoparticles".Comment: Accepted for publication in Phys. Rev. Let

Limits to Linear Price Behaviour: Target Zones for Futures Prices Regulated By Limits

This paper analyzes the random walk behaviour of futures prices when the exchange regulated by price limits. Using a model analogous to exchange rate target zone models, the study tests for the existence of a nonlinear S-shape relation between observed and theoretical futures prices. This phenomenon reflects the adjustment in traders' expectations even when limits are not actually hit. The approach is illustrated for five agricultural futures contracts traded at the Chicago Board of Trade. There is some evidence of nonlinearity in quiet periods. In cases of fundamental realignments, that is volatile periods, this non-liearity disappears.price limits; target zones; gravitation; mean reversion

Rapid roll Inflation with Conformal Coupling

Usual inflation is realized with a slow rolling scalar field minimally coupled to gravity. In contrast, we consider dynamics of a scalar with a flat effective potential, conformally coupled to gravity. Surprisingly, it contains an attractor inflationary solution with the rapidly rolling inflaton field. We discuss models with the conformal inflaton with a flat potential (including hybrid inflation). There is no generation of cosmological fluctuations from the conformally coupled inflaton. We consider realizations of modulated (inhomogeneous reheating) or curvaton cosmological fluctuations in these models. We also implement these unusual features for the popular string-theoretic warped inflationary scenario, based on the interacting D3-anti D3 branes. The original warped brane inflation suffers a large inflaton mass due to conformal coupling to 4-dimensional gravity. Instead of considering this as a problem and trying to cure it with extra engineering, we show that warped inflation with the conformally coupled, rapidly rolling inflaton is yet possible with N=37 efoldings, which requires low energy scales 1-100 TeV of inflation. Coincidentally, the same warping numerology can be responsible for the hierarchy. It is shown that the scalars associated with angular isometries of the warped geometry of compact manifold (e.g. S^3 of KS geometry) have solutions identical to conformally coupled modes and also cannot be responsible for cosmological fluctuations. We discuss other possibilities.Comment: 15 pages, version accepted for publication in PR

Gendered dynamics of international labour migration: migrant women working in Pakistan

Overview There are nearly 8.5 million migrant workers working across different regions of Pakistan, which include both internal and foreign migrant workers. Forty-five per cent of these workers are engaged in informal activities including day labourers, construction workers, domestic helpers, factory workers, informal restaurants, and beauty salons. Pakistan has received a mass influx of people fleeing conflict. The Afghan community is among the largest among undocumented migrants living in the country ( 500,000 as per recent estimates ), followed by a combined population of Bengali, Bangladeshi, and Burmese nationals. Pakistan in not a signatory of the 1951 Refugee Convention and its 1967 Protocol. Additionally, the country lacks a national refugee law, and has therefore been able to avoid granting Afghans clear and defined rights, legal integration, and citizenship. The domestic service sector is one of the largest informal employment sectors in Pakistan. Middle and upper-class households employ women domestic workers, primarily Pakistani domestic workers. However, there are several women workers groups of migrant origin involved in the domestic care industry, for example, such as the ‘Hazara’ in Baluchistan and the Pakistani Bengalis who are Pakistani citizens of Bangladeshi heritage. Pakistan has become an employment destination for Migrant Filipino Domestic Workers (MFDW) , who constitute one of the largest groups among the estimated over 2,000 Filipinos living in Pakistan and of the over 1,000 Filipinos holding a working visa . Despite having a written contractual agreement – that national domestic workers do not hold – literature has shown the absence of labour protections and economic security. Key findings This study is part of a multi-country research project ‘Gendered Dynamics of International Labour Migration’ also involving Turkey, Lebanon, and the Kurdistan Region of Iraq (KRI), which investigated drivers of migration, incorporation into the labour market, experiences of work and living in Pakistan, agency and coping strategies and use of public space. Overall, 22 individual, semi-structured interviews were conducted, predominantly in Islamabad, with adult migrant women with different skill levels, nationalities, and migration experiences. The majority of participants consists of highly skilled and educated migrant women of diverse nationalities who migrated from the Philippines, Canada, China-Korea, Uganda, Germany, Egypt, and Somalia. Among these highly skilled migrants, a good number hold a PhD and/or have professional degrees and worked in formal sectors, i.e., in teaching and as development professionals in international NGOs/UN agencies. Notably, they came to Pakistan for different reasons: family reunification, marriage, independent work and for education and professional opportunities. Of the seven female migrants who worked in domestic and care work, six were MFDW and one was from Tanzania. Most of them, in fact, wanted to find either a job – if they were housewives in their country of origin – or a better paid one, highlighting the lack of opportunities. Most of them had children and providing for them was the chief motivation behind seeking a higher income. Other personal motivations included the desire to escape an unhappy marriage. All Afghan participants worked in the semi-skilled sector as self-employed workers in the service industry, such as beauty salons and carpet-weaving. Gender-based discrimination rooted in social norms, such as those normalising child marriage, or the difficulty of finding the desired employment out of the house, and that are exacerbated by the Taliban regime, is a key driver of migration. A few research participants worked independently as business owners or in service industries. Gender-based discrimination in Pakistan was not openly reported by the migrant women workers who participated in this study, despite those who are married to a Pakistani reporting instances of clashing gender norms. Nearly all describe their living and working conditions in positive terms. Besides the MDWs, a recurrent issue reported is the challenging system in relation to their legal status, which poses several and continuing challenges to obtain and renew their permit. Many migrant workers detailed instances of obstacles that they encountered in their daily life because they were not in possession of the national ID card. On the negative end, there is the case of the undocumented Afghan refugees, living in hiding, and deskilled, who feel socially discriminated against and not integrated in the hosting society. The only two cases of post-migration upskilling are those of two Filipina women both of whom have BAs, one went from being a MDW to establishing her own job agency business (hiring MFDWs), and the other became a swimming coach. Despite the diversity of living and working experiences, including the type of accommodation and living arrangements, most women said that they move around the city freely, using cars or taxis, that they go to restaurants, malls, and markets. For MDWs their process of acquainting with the host country and ‘going out’ to public spaces is filtered by the family they live with, and, to a certain extent, necessarily hampered by their home-based work. The agency of the migrant women in this study can be grasped in all the realms of drivers and processes of migration, the experiences of discrimination at home, their living and working and moving around in Islamabad city, as well as seen as connected to the past, the present and the future as envisaged by the migrant women. Their coping strategies consist in making choices, taking actions, and creating narratives that can mitigate the hardships of their situation in different realms, from the domestic to the workplace. The impact of COVID-19 varied according to the type of work migrant women undertook. It ranged from the possibility of loss or severe reduction of income for those with businesses, being forced to stay inside or working remotely, especially for the group of professionals. For some MFDWs, the workload increased considerably, for others the situation remained unchanged. Interview snapshots An upskilled Filipino migrant woman described becoming more religious and how this led her to fall in love with her Pakistani husband, get married, start their own family of which she is proud, and enjoy her marriage and her new family life. An Afghan migrant woman came instead from a very conservative family, and she was a victim of child and arranged marriage. In Islamabad, she first started working in the family bakery, then as beautician, to end up managing her own salon. A highly educated Algerian migrant woman recounts also a situation of humiliation within the family on behalf of her Pakistani husband’s brother-in-law. In fact, she is very critical of the strong bond that exists between mother and son in the country, and of the patrilocal custom whereby the wife is expected to move in with her in-laws and become their domestic helper. Recommendations More research is needed to understand the conditions and the experiences of women migrant communities, from refugees to professionals, in Pakistan, both in relation to their social and economic contribution to the hosting society, as well as in relation to their internal dynamics and further migration aspirations. Government departments in Pakistan dealing with migrants could be invited to cooperate and compile documents for circulation where they collate their data on migrant communities. ILO, IOM and UNHCR, and other INGOs, could also share their statistics to support delineating a clearer picture of the complex reality of migrants in the country. Evidence-based and migrant-centred programmes of intervention to support the employability and wellbeing of the Afghan community, and other migrant communities, in Pakistan should be strengthened in view of local integration and resettlement. Economic empowerment, legal protection, job security, access to health and social care, social norms changes should be enhanced, in particular targeting hard-to-reach, rural and undocumented communities, and within those, women. The Pakistani government should re-consider signing the 1951 Refugee Convention and its 1967 Protocol. Additionally, the government should work at the drafting of a refugee law. The Pakistani government should revise regulations and policies in relation to the assignment of ID cards to migrant workers, in conjunction with the third sector and employers, to make the permit system more accessible and inclusive

On Metric Preheating

We consider the generation of super-horizon metric fluctuations during an epoch of preheating in the presence of a scalar field \chi quadratically coupled to the inflaton. We find that the requirement of efficient broad resonance is concomitant with a severe damping of super-horizon \delta\chi quantum fluctuations during inflation. Employing perturbation theory with backreaction included as spatial averages to second order in the scalar fields and in the metric, we argue that the usual inflationary prediction for metric perturbations on scales relevant for structure formation is not strongly modified.Comment: 5 latex pages, 1 postscript figure included, uses revtex.sty in two column format and epsf.sty, some typos corrected and references added. Links and further material at http://astro.uchicago.edu/home/web/sigl/r4.htm

Equation of state and Beginning of Thermalization After Preheating

We study the out-of-equilibrium nonlinear dynamics of fields after post-inflationary preheating. During preheating, the energy in the homogeneous inflaton is exponentially rapidly transfered into highly occupied out-of-equilibrium inhomogeneous modes, which subsequently evolve towards equilibrium. The infrared modes excited during preheating evolve towards a saturated distribution long before thermalization completes. We compute the equation of state during and immediately after preheating. It rapidly evolves towards radiation domination long before the actual thermal equilibrium is established. The exact time of this transition is a non-monotonic function of the coupling between the inflaton and the decay products, and it varies only very weakly (around 10^(-35) s) as this coupling changes over several orders of magnitude. This result is applied to refine the relation between the number of efoldings N and the physical wavelength of perturbations generated during inflation. We also discuss the implications for the theory of modulated perturbations from preheating. We finally argue that many questions of the thermal history of the universe should be addressed in terms of pre-thermalization, illustrating this point with a calculation of perturbative production of gravitinos immediately after chaotic inflation. We also highlight the effects of three-legs inflaton interactions on the dynamics of preheating and thermalization in an expanding universe.Comment: 15 pages, 13 figure

Acoustic peaks and dips in the CMB power spectrum: observational data and cosmological constraints

The locations and amplitudes of three acoustic peaks and two dips in the last releases of the Boomerang, MAXIMA and DASI measurements of the cosmic microwave background (CMB) anisotropy power spectra as well as their statistical confidence levels are determined in a model-independent way. It is shown that the Boomerang-2001 data (Netterfield et al. 2001) fixes the location and amplitude of the first acoustic peak at more than 3\sigma confidence level. The next two peaks and dips are determined at a confidence level above 1\sigma but below 2\sigma. The locations and amplitudes of the first three peaks and two dips are 212+/-17, 5426+/-1218\mu K^2, 544+/-56, 2266+/-607\mu K^2, 843+/-35, 2077+/-876\mu K^2, 413+/-50, 1960+/-503\mu K^2, 746+/-89, 1605+/-650\mu K^2 respectively (1\sigma errors include statistical and systematic errors). The MAXIMA and DASI experiments give similar values for the extrema which they determine. The determined cosmological parameters from the CMB acoustic extrema data show good agreement with other determinations, especially with the baryon content as deduced from standard nucleosynthesis constraints. These data supplemented by the constraints from direct measurements of some cosmological parameters and data on large scale structure lead to a best-fit model which agrees with practically all the used experimental data within 1\sigma. The best-fit parameters are: \Omega_{\Lambda}=0.64^{+0.14}_{-0.27}, \Omega_{m}= 0.36^{+0.21}_{-0.11}, \Omega_b=0.047^{+0.093}_{-0.024}, n_s=1.0^{+0.59}_{-0.17}, h=0.65^{+0.35}_{-0.27} and \tau_c=0.15^{+0.95}_{-0.15} (plus/minus values show 1\sigma upper/lower limits obtained by marginalization over all other model parameters). The best-fit values of \Omega_{\nu} and T/S are close to zero, their 1\sigma upper limits are 0.17 and 1.7 respectively.Comment: 34 pages, 10 figures; accepted by ApJ; some corrections in the text are made and a few references are adde

On the new string theory inspired mechanism of generation of cosmological perturbations

Recently a non-inflationary mechanism of generation of scale-free cosmological perturbations of metric was proposed by Brandenberger, Nayeri, and Vafa in the context of the string gas cosmology. We discuss various problems of their model and argue that the cosmological perturbations of metric produced in this model have blue spectrum with a spectral index n = 5, which strongly disagrees with observations. We conclude that this model in its present form is not a viable alternative to inflationary cosmology.Comment: 11 pages, 1 figur