Stylized features of single-nucleon momentum distributions

Nuclear short-range correlations (SRC) typically manifest themselves in the tail parts of the single-nucleon momentum distributions. We propose an approximate practical method for computing those SRC contributions to the high-momentum parts. The framework adopted in this work is applicable throughout the nuclear mass table and corrects mean-field models for central, spin-isospin and tensor correlations by shifting the complexity induced by the SRC from the wave functions to the operators. It is argued that the expansion of these modified operators can be truncated to a low order. The proposed model can generate the SRC-related high-momentum tail of the single-nucleon momentum distribution. These are dominated by correlation operators acting on mean-field pairs with vanishing relative radial and angular-momentum quantum numbers. The proposed method explains the dominant role of proton-neutron pairs in generating the SRC and accounts for the magnitude and mass dependence of SRC as probed in inclusive electron scattering. It also provides predictions for the ratio of the amount of correlated proton-proton to proton-neutron pairs which are in line with the observations. In asymmetric nuclei, the correlations make the average kinetic energy for the minority nucleons larger than for the majority nucleons.Comment: 19 pages, 8 figure

Quantifying short-range correlations in nuclei

Background: Short-range correlations (SRC) are an important ingredient of the dynamics of nuclei. Purpose: An approximate method to quantify the magnitude of the two-nucleon (2N) and three-nucleon (3N) short-range correlations and their mass dependence is proposed. Method: The proposed method relies on the concept of the "universality" or "local nuclear character" of the SRC. We quantify the SRC by computing the number of independent-particle model (IPM) nucleon pairs and triples which reveal beyond-mean-field behavior. It is argued that those can be identified by counting the number of nucleon pairs and triples in a zero relative orbital momentum state. A method to determine the quantum numbers of pairs and triples in an arbitrary mean-field basis is outlined. Results: The mass dependence of the 2N and 3N SRC is studied. The predictions are compared to measurements. This includes the ratio of the inclusive inelastic electron scattering cross sections of nuclei to H-2 and He-3 at large values of the Bjorken variable. Corrections stemming from the center-of-mass motion of the pairs are estimated. Conclusions: We find that the relative probability per nucleon for 2N and 3N SRC has a soft dependence with mass number A and that the proton-neutron 2N SRC outnumber the proton-proton (neutron-neutron) 2N SRC. A linear relationship between the magnitude of the EMC effect and the predicted number of proton-neutron SRC pairs is observed. This provides support for the role of local nuclear dynamics on the EMC effect

Mass dependence of short-range correlations in nuclei and the EMC effect

An approximate method to quantify the mass dependence of the number of two-nucleon (2N) short-range correlations (SRC) in nuclei is suggested. The proposed method relies on the concept of the "local nuclear character" of the SRC. We quantify the SRC and its mass dependence by computing the number of independent-particle model (IPM) nucleon pairs in a zero relative orbital momentum state. We find that the relative probability per nucleon for 2N SRC follows a power law as a function of the mass number $A$. The predictions are connected to measurements which provide access to the mass dependence of SRC. First, the ratio of the inclusive inelastic electron scattering cross sections of nuclei to $^{2}$H at large values of the Bjorken variable. Second, the EMC effect, for which we find a linear relationship between its magnitude and the predicted number of SRC-prone pairs.Comment: 12 pages, 4 figures, preprint proceeding Thirty First International Workshop on Nuclear Theory (IWNT31-2012), organized by the Nuclear Theory Laboratory of the Institute for Nuclear Research and Nuclear Energy of the Bulgarian Academy of Science

Prospective associations between loneliness and emotional intelligence

Loneliness has been linked cross-sectionally to emotional skill deficits (e.g., Zysberg, 2012), but missing from the literature is a longitudinal examination of these relationships. The present study fills that gap by examining the prospective relationships between loneliness and emotional functioning in young adolescents in England. One hundred and ninety-six adolescents aged 11-13 years (90 females) took part in the study and completed the youth version of the Mayer-Salovey-Caruso Emotional Intelligence Test (MSCEIT-YV) and the peer-related subscale of the Loneliness and Aloneness Scale for Children and Adolescents (LACA) at two time points, which were 10 months apart. Prospective associations were obtained for male and female adolescents separately using cross-lagged statistical techniques. Our results showed prospective links between understanding and managing emotions and loneliness for both females and males. Perceiving and using emotions were prospectively linked to loneliness in males only. Possible explanations and directions for future research are discussed

What densities can be effectively probed in quasifree single-nucleon knockout reactions?

We address the issue whether quasifree single-nucleon knockout measurements carry sufficient information about the nuclear interior. To this end, we present comparisons of the reaction probability densities for $A(e,e'p)$ and $A(p,2p)$ in quasifree kinematics for the target nuclei $^{4}$He, $^{12}$C, $^{56}$Fe, and $^{208}$Pb. We adopt a comprehensive framework based on the impulse approximation and on a relativized extension of Glauber multiple-scattering reaction theory in which the medium effects related to short-range correlations (SRC) are implemented. It is demonstrated that SRC weaken the effect of attenuation. For light target nuclei, both the quasifree $(p,2p)$ and $(e,e'p)$ can probe average densities of the same order as nuclear saturation density $\rho_{0}$. For heavy nuclei like $^{208}$Pb, the probed average densities are smaller than $0.1\rho_{0}$ and the $(e,e'p)$ reaction is far more efficient in probing the bulk regions than $(p,2p)$.Comment: 11 pages, 12 figure

Loneliness Across the Life Span

Most people have experienced loneliness and have been able to overcome it to reconnect with other people. In the current review, we provide a life-span perspective on one component of the evolutionary theory of loneliness—a component we refer to as the reaffiliation motive (RAM). The RAM represents the motivation to reconnect with others that is triggered by perceived social isolation. Loneliness is often a transient experience because the RAM leads to reconnection, but sometimes this motivation can fail, leading to prolonged loneliness. We review evidence of how aspects of the RAM change across development and how these aspects can fail for different reasons across the life span. We conclude with a discussion of age-appropriate interventions that may help to alleviate prolonged lonelines

Reliability and validity of the Roberts UCLA Loneliness Scale (RULS-8) with Dutch-speaking adolescents in Belgium

The internal consistency and construct validity of the RULS-8, a brief measure of loneliness for use with adolescents, was examined in three samples of Dutch-speaking adolescents in Belgium (for a total of 'N' = 6,236). The measure showed high levels of internal consistency (ranging between .80 and .82), strong convergence with the original 20-item instrument ('r' = .92; Sample 1; 'N' = 282), excellent fit with its hypothesized factor structure through confirmatory factor analysis (Sample 2; 'N' = 1,144), measurement invariance across gender, and significant correlations in the expected direction with a set of indicators of psychological adaptation and maladaptation (Sample 3; 'N' = 4,810). Based on these results, the 8-item short form is recommended for use with Dutch-speaking adolescents when administration of the full form seems less advisable due to time constraints. Suggestions for potential use of the short form and for future research on its reliability and validity are outlined

Parent-Adolescent Discrepancies Regarding Adolescents' Peer-Related Loneliness:Associations with Adolescent Adjustment

Because loneliness is a subjective experience, it is often examined using self-reports. Yet, researchers have started to use other-reports to examine loneliness. As previous research suggests that discrepancies between self- and other views might have important implications for adolescents' mental health, the current study examines discrepancies in multi-informant reports on adolescents' loneliness in relation with prosocial behavior, aggression, and adolescents' parent-related loneliness. The sample consisted of 374 mother-adolescent dyads and 318 father-adolescent dyads (41.80% male, M (age) = 15.67 years, SD = 1.25). Results indicated that informants used different reference points to assess adolescents' peer-related loneliness, but were otherwise comparable. Moreover, informant discrepancies were associated with greater adolescents' reported parent-related loneliness. The current study did not provide evidence that discrepancies were related to prosocial or aggressive behavior. The current study adds to the notion that other-reports on loneliness show substantial convergence with self-reports. In addition, this study indicates that the discrepancy between other- and self-reports on loneliness holds valuable information for adolescent socio-emotional adjustment.</p