Renormalization by Continuous Unitary Transformations: One-Dimensional Spinless Fermions

A renormalization scheme for interacting fermionic systems is presented where the renormalization is carried out in terms of the fermionic degrees of freedom. The scheme is based on continuous unitary transformations of the hamiltonian which stays hermitian throughout the renormalization flow, whereby any frequency dependence is avoided. The approach is illustrated in detail for a model of spinless fermions with nearest neighbour repulsion in one dimension. Even though the fermionic degrees of freedom do not provide an easy starting point in one dimension very good results are obtained which agree well with the exact findings based on Bethe ansatz.Comment: 17 pages, figures included some revisions concerning the comparison to other methods, references update

Mapping the origins of time: Scalar errors in infant time estimation

Time is central to any understanding of the world. In adults, estimation errors grow linearly with the length of the interval, much faster than would be expected of a clock-like mechanism. Here we present the first direct demonstration that this is also true in human infants. Using an eye-tracking paradigm, we examined 4-, 6-, 10-, and 14-month-olds' responses to the omission of a recurring target, on either a 3- or 5-s cycle. At all ages (a) both fixation and pupil dilation measures were time locked to the periodicity of the test interval, and (b) estimation errors grew linearly with the length of the interval, suggesting that trademark interval timing is in place from 4 months

Experimental realization of a momentum-space quantum walk

We report on a discrete-time quantum walk that uses the momentum of ultra-cold rubidium-87 atoms as the walk space and two internal atomic states as the coin degree of freedom. Each step of the walk consists of a coin toss (a microwave pulse) followed by a unitary shift operator (a resonant ratchet pulse). We carry out a comprehensive experimental study on the effects of various parameters, including the strength of the shift operation, coin parameters, noise, and initialization of the system on the behavior of the walk. The walk dynamics can be well controlled in our experiment; potential applications include atom interferometry and engineering asymmetric walks.Comment: 11 pages, 11 figure

Thermodynamics of nano-spheres encapsulated in virus capsids

We investigate the thermodynamics of complexation of functionalized charged nano-spheres with viral proteins. The physics of this problem is governed by electrostatic interaction between the proteins and the nano-sphere cores (screened by salt ions), but also by configurational degrees of freedom of the charged protein N-tails. We approach the problem by constructing an appropriate complexation free energy functional. On the basis of both numerical and analytical studies of this functional we construct the phase diagram for the assembly which contains the information on the assembled structures that appear in the thermodynamical equilibrium, depending on the size and surface charge density of the nano-sphere cores. We show that both the nano-sphere core charge as well as its radius determine the size of the capsid that forms around the core.Comment: Submitte

Using case formulation for prediction of the therapeutic alliance in treatment for borderline personality disorder.

Case formulation is a central tool for psychotherapists, which helps them tailor psychotherapy to the individual patient, particularly for treatments for complex and multilayered clinical problems, such as personality disorders (Kramer, 2019). Case formulation methodologies are still underutilized in psychotherapy research in the prediction of therapy processes. The present study included N = 60 patients with borderline personality disorder undergoing a brief treatment using an individualized treatment component (n = 31), as compared with a standard brief treatment (n = 29; Kramer et al., 2014). For each patient (in both groups as post hoc analysis based on videos), we performed a Plan analysis case formulation (Caspar, 2019): the idiographic information from the formulation was translated into quantitative scores (on a Likert-type scale) assessing patient's interactional agreeableness (vs. antagonism; Zufferey et al., 2019). We modeled the session-by-session predictions of the progression of the therapeutic alliance-rated by the patient and the therapist-over the course of treatment, as a function of interactional agreeableness, the individualization of treatment, as well as their interaction with the session number. Patients with high levels of agreeableness have a significant increase in their alliance assessment over time. Treatment based on the case formulation predicted session-by-session increase of the therapeutic alliance as rated by the therapists. This study was the first to explore intra- and interindividual dynamics of the therapeutic alliance in relationship with idiographic information extracted from case formulations. The results may help understand relationship struggles at the beginning of therapy for complex clinical problems, such as borderline personality disorder. (PsycInfo Database Record (c) 2022 APA, all rights reserved)

Clinical features and multidisciplinary approaches to dementia care

Dementia is a clinical syndrome of widespread progressive deterioration of cognitive abilities and normal daily functioning. These cognitive and behavioral impairments pose considerable challenges to individuals with dementia, along with their family members and caregivers. Four primary dementia classifications have been defined according to clinical and research criteria: 1) Alzheimer’s disease; 2) vascular dementias; 3) frontotemporal dementias; and 4) dementia with Lewy bodies/Parkinson’s disease dementia. The cumulative efforts of multidisciplinary healthcare teams have advanced our understanding of dementia beyond basic descriptions, towards a more complete elucidation of risk factors, clinical symptoms, and neuropathological correlates. The characterization of disease subtypes has facilitated targeted management strategies, advanced treatments, and symptomatic care for individuals affected by dementia. This review briefly summarizes the current state of knowledge and directions of dementia research and clinical practice. We provide a description of the risk factors, clinical presentation, and differential diagnosis of dementia. A summary of multidisciplinary team approaches to dementia care is outlined, including management strategies for the treatment of cognitive impairments, functional deficits, and behavioral and psychological symptoms of dementia. The needs of individuals with dementia are extensive, often requiring care beyond traditional bounds of medical practice, including pharmacologic and non-pharmacologic management interventions. Finally, advanced research on the early prodromal phase of dementia is reviewed, with a focus on change-point models, trajectories of cognitive change, and threshold models of pathological burden. Future research goals are outlined, with a call to action for social policy initiatives that promote preventive lifestyle behaviors, and healthcare programs that will support the growing number of individuals affected by dementia

Steering random walks with kicked ultracold atoms

A kicking sequence of the atom optics kicked rotor at quantum resonance can be interpreted as a quantum random walk in momentum space. We show how to steer such a random walk by applying a random sequence of intensities and phases of the kicking lattice chosen according to a probability distribution. This distribution converts on average into the final momentum distribution of the kicked atoms. In particular, it is shown that a power-law distribution for the kicking strengths results in a L\'evy walk in momentum space and in a power-law with the same exponent in the averaged momentum distribution. Furthermore, we investigate the stability of our predictions in the context of a realistic experiment with Bose-Einstein condensates.Comment: detailed study of random walks and their implementation with a Bose condensate, 12 pages, 7 figure

Soft modes near the buckling transition of icosahedral shells

Icosahedral shells undergo a buckling transition as the ratio of Young's modulus to bending stiffness increases. Strong bending stiffness favors smooth, nearly spherical shapes, while weak bending stiffness leads to a sharply faceted icosahedral shape. Based on the phonon spectrum of a simplified mass-and-spring model of the shell, we interpret the transition from smooth to faceted as a soft-mode transition. In contrast to the case of a disclinated planar network where the transition is sharply defined, the mean curvature of the sphere smooths the transitition. We define elastic susceptibilities as the response to forces applied at vertices, edges and faces of an icosahedron. At the soft-mode transition the vertex susceptibility is the largest, but as the shell becomes more faceted the edge and face susceptibilities greatly exceed the vertex susceptibility. Limiting behaviors of the susceptibilities are analyzed and related to the ridge-scaling behavior of elastic sheets. Our results apply to virus capsids, liposomes with crystalline order and other shell-like structures with icosahedral symmetry.Comment: 28 pages, 6 figure

Haagse pionnen op het Brusselse schaakbord?

Samenvatting In dit artikel komt het vraagstuk van de ambtelijke autonomie van geëuropeaniseerde rijksambtenaren aan de orde. Als casus wordt de politieke en ambtelijke aansturing van Nederlandse rijksambtenaren die gedetacheerd worden bij de Europese Commissie (END-ers) onderzocht. Het empirisch materiaal bestaat uit survey-data (N = 90) en interviewdata (N = 28), verkregen van zowel huidige als voormalige END-ers. Op grond van dit materiaal wordt betoogd dat hoewel van formele aansturing vanuit de lidstaat geen sprake kan zijn, de END-ers in de praktijk een duidelijke brugfunctie vervullen tussen beide bestuurslagen. Dit kan gebeuren door middel van zowel frontloaden (bewust, na instructies van de nationale overheid, of onbewust, als gevolg van het nationaal-culturele perspectief) als signaleren (strategisch informatie en standpunten doorseinen van de ene bestuurslaag naar de andere). Hoewel de contacten van de END-er met de Commissie vaak redelijk overeind blijven na terugkomst, neemt de intensiteit van de contacten met andere typen actoren in het beleidsnetwerk meestal snel af

Bridge-builders or Bridgeheads in Brussels? The World of Seconded National Experts

Introduction:The foregoing chapters of this book have demonstrated the extent to which national civil servants are involved in EU-related activities, and the dynamics of national administrative activities in the context of the EU. This chapter shifts the focus from national civil servants working on the European Union to national civil servants working for the European Union. This is a class of national civil servants for whom finding a balance between national and European interests in their work is a permanent, although sometimes implicit feature of their daily professional activities. The duality of national and European roles is perhaps the most exacerbated for the seconded national experts (SNEs), i.e. national civil servants who are temporarily working for EU institutions, in particular those seconded to the European Commission.2 On the one hand, Commission SNEs have to be loyal to the Commission and represent European interests in this supranational organ of the EU. On the other hand, their employer is still the member-state government, and they are expected to return to their home organization after their secondment term ends. The SNEs are thus practically torn between two employers: their daily employer under whose supervision they work (the Commission) and the national employer who sent them on the secondment and continues to pay their salaries (the member-state)