How to Be Okay

I began this line of thought with the desire to understand human connection. I want to know how people operate both as individuals being perceived as well as how they connect to each other in small, casual ways. Acts like introducing yourself, or navigating in a crowded place seemed like skills that everyone had learned on the day I had skipped class. This began as a private venture, an intensifying of my day to day attempts of applied observation. My result, rather than gradual mastery of interpersonal relations, was deeper confusion and frustration. I wanted instruction, but the construction of instructions lead me farther from my goal as I became hyper-aware of my own movements and interactions to the point of paralyzation. Something about this tickled me, instructions in which their failure was not their lack of specificity or clarity, but rather the over abundance of information. The concept of ineffective instruction lead me to the idea of solutions, not just through understanding and instruction, but objects. These objects, such as a “thicker skin” began to depart from the laws of our world, but are based in the language used to express intangible ideas and entertain a “what-if” notion. The language surrounding emotional states, personality and interpersonal relations often is a figurative usage of words typically applied to objects. Word play takes a role in both complicating ideas, by presenting two sides of a word as well as opening a passage for humor, a quiet acknowledge of the absurdity I saw in the complications of what seemed to be basic functions. Word play is in part how string became a central element of this body of work. Initially string was suggested as an alternative to Sharpie, but then I realized its relation with connection, and its ability to subtle suggest connections or “ties”, suiting it perfectly for illustration of attempts of human connection as in figures outlining the steps of hand holding. String also became the medium for a large wall drawing. Again, the medium served to suggest connection, while also playing with the idea of a thread of thought. In addition the scale of the drawing in relation to the meticulous attention that needed to be paid to the material, embodied the obsessive and overthought nature of the project. As my thoughts developed, I became increasingly aware of the simultaneous and opposing forces of connection and disconnection. I saw this particularly in physical contact, how a physical act can be either devoid of emotion or extremely emotionally intimate and that the physical actions do not necessarily correlate with the degree of emotional intimacy. In moments of intimacy we still have a physical barrier, skin, that separates us. I began thinking of skin in the sense of a barrier with varying levels of permeability, both with the possibility of protection as well as vulnerability. Using the transparency of kozo paper, I imagined the possibilities of passing the skin barrier and the transparency and delicacy of the barrier. This idea was also worked in the opposite direction with the creation of a “thicker skin”, with the possibility of increased protection. In the development of this project I became aware of the connection established by disconnection. Initially beginning as a private investigation, and then evolving into a realization of the universality of the struggle for connection and the possible resulting empathy from this realization

The formation of black hole low-mass X-ray binaries: through case B or case C mass transfer?

The formation of low-mass X-ray binaries containing a rather massive (M >~ 7 \msun) black hole is problematic because in most recent stellar evolutionary calculations the immediate progenitors of these black holes (Wolf-Rayet stars) lose so much mass via their stellar wind that their final masses are well below the observed black hole masses. We discuss the recently proposed solution that these binaries are formed through case C mass transfer (i.e. mass transfer after core helium burning is completed), avoiding a long Wolf-Rayet phase and thus significant mass loss. We show that only some of the currently available models for the evolution of massive stars allow this formation channel. We also investigate the effect of the downward revised Wolf-Rayet mass-loss rate as is suggested by observations, and conclude that in that case Wolf-Rayet stars end their lives with significantly higher masses than previously found and may be able to form a black holes.Comment: Accepted for publication by A&

Complete spectrum of the infinite-UU Hubbard ring using group theory

We present a full analytical solution of the multiconfigurational strongly-correlated mixed-valence problem corresponding to the $N$-Hubbard ring filled with $N-1$ electrons, and infinite on-site repulsion. While the eigenvalues and the eigenstates of the model are known already, analytical determination of their degeneracy is presented here for the first time. The full solution, including degeneracy count, is achieved for each spin configuration by mapping the Hubbard model into a set of Huckel-annulene problems for rings of variable size. The number and size of these effective Huckel annulenes, both crucial to obtain Hubbard states and their degeneracy, are determined by solving a well-known combinatorial enumeration problem, the necklace problem for $N-1$ beads and two colors, within each subgroup of the $C_{N-1}$ permutation group. Symmetry-adapted solution of the necklace enumeration problem is finally achieved by means of the subduction of coset representation technique [S. Fujita, Theor. Chim. Acta 76, 247 (1989)], which provides a general and elegant strategy to solve the one-hole infinite-$U$ Hubbard problem, including degeneracy count, for any ring size. The proposed group theoretical strategy to solve the infinite-$U$ Hubbard problem for $N-1$ electrons, is easily generalized to the case of arbitrary electron count $L$, by analyzing the permutation group $C_L$ and all its subgroups.Comment: 31 pages, 4 figures. Submitte

The effects of visual feedback during a rhythmic weight-shifting task in patients with Parkinson's disease

Augmented visual feedback (VF) may offer benefits similar to those of rhythmic external cues in alleviating some mobility-related difficulties in individuals with Parkinson’s disease (PD). However, due to an impaired ability to reweigh sensory information under changing circumstances, subjects with PD may be rather vulnerable to incongruity of visual information. In the present study, we investigatedwhether VF is indeed effective in improving motor functioning in a weight-shifting task during upright stance, and whether subjects with PD are affected more by incongruent VF than healthy controls. Participants performed sideways swaying motions based on tracking of real-time and delayed VF – the first providing congruent, and hence more accurate, visual information than the latter. We analyzed center-of-pressure signals patterns for 28 individuals with PD and 16 healthy, age- and gender-matched controls by estimating task accuracy, movement pattern variability, and normalized movement amplitude. For conditions without feedback and with real-time feedback, subjects with PD performed lateral swaying motions with greater error (F(1, 42) = 12.065, p = .001) and with more variablemovement patterns than healthy controls (F(1, 24) = 113.086, p < .001). Error change scores revealed that patients with PD were nevertheless still able to use VF to improve tracking performance (t(24) = 2.366, p = .026). However, whereas controls were able to adapt to a certain amount of visual incongruity, patients with PD were not. Instead, movement amplitude was significantly reduced in this group (F(1.448, 60.820) = 17.639, p < .001). By reducing movement amplitude, subjects with PD appear to resort to a ‘conservative’ strategy to minimize performance breakdown

Evolution of Neutron-Star, Carbon-Oxygen White-Dwarf Binaries

At least one, but more likely two or more, eccentric neutron-star, carbon-oxygen white-dwarf binaries with an unrecycled pulsar have been observed. According to the standard scenario for evolving neutron stars which are recycled in common envelope evolution we expect to observe \gsim 50 such circular neutron star-carbon oxygen white dwarf binaries, since their formation rate is roughly equal to that of the eccentric binaries and the time over which they can be observed is two orders of magnitude longer, as we shall outline. We observe at most one or two such circular binaries and from that we conclude that the standard scenario must be revised. Introducing hypercritical accretion into common envelope evolution removes the discrepancy by converting the neutron star into a black hole which does not emit radio waves, and therefore would not be observed.Comment: 25 pages, 1 figure, accepted in Ap

The origin of the runaway high-mass X-ray binary HD153919/4U1700-37

Based on its Hipparcos proper motion, we propose that the high-mass X-ray binary HD153919/4U1700-37 originates in the OB association Sco OB1. At a distance of 1.9 kpc the space velocity of 4U1700-37 with respect to Sco OB1 is 75 km/s. This runaway velocity indicates that the progenitor of the compact X-ray source lost about 7 Msun during the (assumed symmetric) supernova explosion. The system's kinematical age is about 2 +/- 0.5 million years which marks the date of the supernova explosion forming the compact object. The present age of Sco OB1 is <8 Myr; its suggested core, NGC 6231, seems to be somewhat younger (~5 Myr). If HD153919/4U1700-37 was born as a member of Sco OB1, this implies that the initially most massive star in the system terminated its evolution within 30 Msun. With these parameters the evolution of the binary system can be constrained.Comment: 6 pages, latex, 3 embedded ps figures, to appear in A&

Formation of Millisecond Pulsars with Heavy White Dwarf Companions: Extreme Mass Transfer on Sub-Thermal Timescales

We have performed detailed numerical calculations of the non-conservative evolution of close X-ray binary systems with intermediate-mass (2.0-6.0 M_sun) donor stars and a 1.3 M_sun accreting neutron star. We calculated the thermal response of the donor star to mass loss, in order to determine its stability and follow the evolution of the mass transfer. Under the assumption of the "isotropic re-emission model" we demonstrate that in many cases it is possible for the binary to prevent a spiral-in and survive a highly super-Eddington mass-transfer phase (1 << M_dot/M_Edd < 10^5) on a sub-thermal timescale, if the convective envelope of the donor star is not too deep. These systems thus provide a new formation channel for binary millisecond pulsars with heavy CO white dwarfs and relatively short orbital periods (3-50 days). However, we conclude that to produce a binary pulsar with a O-Ne-Mg white dwarf or P_orb ~1 day (e.g. PSR B0655+64) the above scenario does not work, and a spiral-in phase is still considered the most plausible scenario for the formation of such a system