Measurement of BOLD changes due to cued eye-closure and stopping during a continuous visuomotor task via model-based and model-free approaches

As a precursor for investigation of changes in neural activity underlying lapses of responsiveness, we set up a system to simultaneously record functional magnetic resonance imaging (fMRI), eye-video, EOG, and continuous visuomotor response inside an MRI scanner. The BOLD fMRI signal was acquired during a novel 2-D tracking task in which participants (10 males, 10 females) were cued to either briefly stop tracking and close their eyes (Stop Close) or to briefly stop tracking (Stop) only. The onset and duration of eye-closure and stopping were identified post hoc from eye-video, EOG, and visuomotor response. fMRI data were analyzed using a general linear model (GLM) and tensorial independent component analysis (TICA). The GLM-based analysis identified predominantly increased blood oxygenation level dependent (BOLD) activity during eye-closure and stopping in multisensory areas, sensory-motor integration areas, and default-mode regions. Stopping during tracking elicited increased activity in visual processing areas, sensory-motor integration areas, and premotor areas. TICA separated the spatio-temporal pattern of activity into multiple task-related networks including the 1) occipito-medial frontal eye-movement network, 2) sensory areas, 3) left-lateralized visuomotor network, and 4) fronto-parietal visuomotor network, which were modulated differently by Stop Close and Stop. The results demonstrate the merits of using simultaneous fMRI, behavioral, and physiological recordings to investigate the mechanisms underlying complex human behaviors in the human brain. Furthermore, knowledge of widespread modulations in brain activity due to voluntary eye-closure or stopping during a continuous visuomotor task is important for studies of the brain mechanisms underlying involuntary behaviors, such as microsleeps and attention lapses, which are often accompanied by brief eye-closure and/or response failures

String production after angled brane inflation

We describe string production after angled brane inflation. First, we point out that there was a discrepancy in previous discussions. The expected tension of the cosmic string calculated from the four-dimensional effective Lagrangian did not match the one obtained in the brane analysis. In the previous analysis, the cosmic string is assumed to correspond to the lower-dimensional daughter brane, which wraps the same compactified space as the original mother brane. In this case, however, the tension of the daughter brane cannot depend on the angle (\theta). On the other hand, from the analysis of the effective Lagrangian for tachyon condensation, it is easy to see that the tension of the cosmic string must be proportional to \theta, when \theta << 1. This is an obvious discrepancy that must be explained by consideration of the explicit brane dynamics. In this paper, we will solve this problem by introducing a simple idea. We calculate the tension of the string in the two cases, which matches precisely. The cosmological constraint for angled inflation is relaxed, because the expected tension of the cosmic string becomes smaller than the one obtained in previous arguments, by a factor of \theta.Comment: 13pages, 3 figures, typos correcte

Cosmic microwave background and large scale structure limits on the interaction between dark matter and baryons

We study the effect on the cosmic microwave background (CMB) anisotropy and large scale structure (LSS) power spectrum of a scattering interaction between cold dark matter and baryons. This scattering alters the CMB anisotropy and LSS spectrum through momentum transfer between the cold dark matter particles and the baryons. We find that current CMB observations can put an upper limit on the scattering cross section which is comparable with or slightly stronger than previous disk heating constraints at masses greater than 1 GeV, and much stronger at smaller masses. When large-scale structure constraints are added to the CMB limits, our constraint is more stringent than this previous limit at all masses. In particular, a dark matter-baryon scattering cross section comparable to the ``Spergel-Steinhardt'' cross section is ruled out for dark matter mass greater than 1 GeV.Comment: 8 pages, 2 figures, use RevTeX4, submitted to PRD replaced with revised versio

Q ball inflation

We show that inflation can occur in the core of a Q-ball.Comment: 11 pages, latex2e, no figure, references added, final version to appear in PR

Astrophysical Reaction Rates for 10^{10}B(p,α\alpha)7^{7}Be and 11^{11}B(p,α\alpha)8^{8}Be From a Direct Model

The reactions $^{10}$B(p,$\alpha$)$^{7}$Be and $^{11}$B(p,$\alpha$)$^{8}$Be are studied at thermonuclear energies using DWBA calculations. For both reactions, transitions to the ground states and first excited states are investigated. In the case of $^{10}$B(p,$\alpha$)$^{7}$Be, a resonance at $E_{Res}=10$ keV can be consistently described in the potential model, thereby allowing the extension of the astrophysical $S$-factor data to very low energies. Strong interference with a resonance at about $E_{Res}=550$ keV require a Breit-Wigner description of that resonance and the introduction of an interference term for the reaction $^{10}$B(p,$\alpha_1$)$^{7}$Be$^*$. Two isospin $T=1$ resonances (at $E_{Res1}=149$ keV and $E_{Res2}=619$ keV) observed in the $^{11}$B+p reactions necessitate Breit-Wigner resonance and interference terms to fit the data of the $^{11}$B(p,$\alpha$)$^{8}$Be reaction. $S$-factors and thermonuclear reaction rates are given for each reaction. The present calculation is the first consistent parametrization for the transition to the ground states and first excited states at low energies.Comment: 27 pages, 5 Postscript figures, uses RevTex and aps.sty; preprint also available at http://quasar.physik.unibas.ch/ Phys. Rev. C, in pres

Computational Nuclear Physics and Post Hartree-Fock Methods

We present a computational approach to infinite nuclear matter employing Hartree-Fock theory, many-body perturbation theory and coupled cluster theory. These lectures are closely linked with those of chapters 9, 10 and 11 and serve as input for the correlation functions employed in Monte Carlo calculations in chapter 9, the in-medium similarity renormalization group theory of dense fermionic systems of chapter 10 and the Green's function approach in chapter 11. We provide extensive code examples and benchmark calculations, allowing thereby an eventual reader to start writing her/his own codes. We start with an object-oriented serial code and end with discussions on strategies for porting the code to present and planned high-performance computing facilities.Comment: 82 pages, to appear in Lecture Notes in Physics (Springer), "An advanced course in computational nuclear physics: Bridging the scales from quarks to neutron stars", M. Hjorth-Jensen, M. P. Lombardo, U. van Kolck, Editor

Baryon number violation, baryogenesis and defects with extra dimensions

In generic models for grand unified theories(GUT), various types of baryon number violating processes are expected when quarks and leptons propagate in the background of GUT strings. On the other hand, in models with large extra dimensions, the baryon number violation in the background of a string is not trivial because it must depend on the mechanism of the proton stabilization. In this paper we argue that cosmic strings in models with extra dimensions can enhance the baryon number violation to a phenomenologically interesting level, if the proton decay is suppressed by the mechanism of localized wavefunctions. We also make some comments on baryogenesis mediated by cosmological defects. We show at least two scenarios will be successful in this direction. One is the scenario of leptogenesis where the required lepton number conversion is mediated by cosmic strings, and the other is the baryogenesis from the decaying cosmological domain wall. Both scenarios are new and have not been discussed in the past.Comment: 20pages, latex2e, comments and references added, to appear in PR

Hybridized Affleck-Dine baryogenesis

We propose a novel scenario for Affleck-Dine baryogenesis in the braneworld, considering the hybrid potential for the Affleck-Dine field. Destabilization of the flat direction is not due to the Hubble parameter, but is induced by a trigger field. The moduli for the brane distance plays the role of the trigger field. Q-balls are unstable in models with large extra dimensions.Comment: 10pages, plain latex2e, references added, to appear in PR

Thermal leptogenesis in a model with mass varying neutrinos

In this paper we consider the possibility of neutrino mass varying during the evolution of the Universe and study its implications on leptogenesis. Specifically, we take the minimal seesaw model of neutrino masses and introduce a coupling between the right-handed neutrinos and the dark energy scalar field, the Quintessence. In our model, the right-handed neutrino masses change as the Quintessence scalar evolves. We then examine in detail the parameter space of this model allowed by the observed baryon number asymmetry. Our results show that it is possible to lower the reheating temperature in this scenario in comparison with the case that the neutrino masses are unchanged, which helps solve the gravitino problem. Furthermore, a degenerate neutrino mass patten with $m_i$ larger than the upper limit given in the minimal leptogenesis scenario is permitted.Comment: 18 pages, 7 figures, version to appear in PR

Standard Model baryogenesis through four-fermion operators in braneworlds

We study a new baryogenesis scenario in a class of braneworld models with low fundamental scale, which typically have difficulty with baryogenesis. The scenario is characterized by its minimal nature: the field content is that of the Standard Model and all interactions consistent with the gauge symmetry are admitted. Baryon number is violated via a dimension-6 proton decay operator, suppressed today by the mechanism of quark-lepton separation in extra dimensions; we assume that this operator was unsuppressed in the early Universe due to a time-dependent quark-lepton separation. The source of CP violation is the CKM matrix, in combination with the dimension-6 operators. We find that almost independently of cosmology, sufficient baryogenesis is nearly impossible in such a scenario if the fundamental scale is above 100 TeV, as required by an unsuppressed neutron-antineutron oscillation operator. The only exception producing sufficient baryon asymmetry is a scenario involving out-of-equilibrium c quarks interacting with equilibrium b quarks.Comment: 39 pages, 5 figures v2: typos, presentational changes, references and acknowledgments adde