Thermodynamic potential of the Periodic Anderson Model with the X-boson method: Chain Approximation

The Periodic Anderson Model (PAM) in the $U\to\infty$ limit has been studied in a previous work employing the cumulant expansion with the hybridization as perturbation (M. S. Figueira, M. E. Foglio and G. G. Martinez, Phys. Rev. B \textbf{50}, 17933 (1994)). When the total number of electrons $N_{t}$ is calculated as a function of the chemical potential $\mu$ in the ``Chain Approximation'' (CHA), there are three values of the chemical potential $\mu$ for each $N_{t}$ in a small interval of $N_{t}$ at low $T$ (M. S Figueira, M. E Foglio, Physica A 208 (1994)). We have recently introduced the ``X-boson'' method, inspired in the slave boson technique of Coleman, that solves the problem of non conservation of probability (completeness) in the CHA as well as removing the spurious phase transitions that appear with the slave boson method in the mean field approximation. In the present paper we show that the X-boson method solves also the problem of the multiple roots of $N_{t}(\mu)$ that appear in the CHA.Comment: 13 pages, 6 figures e-mails: [email protected], [email protected], [email protected]

Hawking-Unruh effect and the entanglement of two-mode squeezed states in Riemannian spacetime

We consider the system of free scalar field, which is assumed to be a two-mode squeezed state from an inertial point of view. This setting allows the use of entanglement measure for continuous variables, which can be applied to discuss free and bound entanglement from the point of view from non-inertial observer.Comment: Phys. Lett. A, accepted for publicatio

Evaluation of concrete modeling in LS-DYNA for seismic application

LS-DYNA is a versatile finite element analysis program that can be used as a highly effective tool for solving a wide range of structural engineering problems. The software’s capabilities are highly desirable for studying the response of structures under earthquakes due to the large number of independent design parameters that can be considered. Because LS-DYNA has been utilized primarily for blast and impact simulations, however, limited effort has been expended to validate the material models used within the software for seismic-resistant design applications. The objective of this study was to evaluate the performance of four commonly used LS-DYNA concrete models (MAT 072R3, MAT 084, MAT 159, and MAT 272) for seismic applications. The first phase of analysis used individual elements to demonstrate the effects of element size, element formulation, hourglass formulation, and strain application rate on each material model’s performance. Additional single-element analyses were conducted to investigate each model’s capability to accurately capture different components of seismic loading, such as shear, cyclic compression, and cyclic load reversal. This single-element study yielded a collection of strengths and weaknesses associated with each material vii model. The second phase of analysis investigated how the strengths and weaknesses identified in the single-element analyses applied to multi-element simulations. This portion of the research was accomplished by replicating two experimental programs and observing and analyzing the differences between the generated numerical results and the documented experimental results. Based on observations from the single-element and multi-element studies, a series of limitations and recommendations pertaining to each material model were developed. MAT 072R3 and MAT 272 were not recommended for use with seismic applications due to damage accumulation limitations and hourglass control restrictions, respectively. Both MAT 084 and MAT 159 demonstrated they include all the necessary capabilities to be used for seismic problems; nonetheless, users should understand that there is some inherent error when applying these models. Additionally, it was observed that both MAT 084 and MAT 159 overpredicted energy dissipation by more than 200%. As a result, the current version of LS-DYNA is not recommended for problems with imposed acceleration histories.Civil, Architectural, and Environmental Engineerin

Relative Age Effects on Attention-Deficit/Hyperactivity Disorder Symptoms and Educational Achievement:A Longitudinal UK Cohort Study

ObjectiveBeing among the youngest in a school class increases the risk for worse educational outcomes and attention-deficit/hyperactivity disorder (ADHD) symptoms, but questions remain about the nature and persistence of such effects. We investigated this “relative age effect” on educational achievement at age 15 to 16 years and on ADHD symptoms from age 7 to age 21 years. Furthermore, we examined whether being young-in-class is linked to a greater reduction in ADHD symptoms from childhood to adulthood and a lower genetic propensity to ADHD.MethodWe identified 3,928 young-in-class and 4,580 old-in-class participants from the Twins’ Early Development Study. Educational achievement was measured with mathematics and English examination grades at age 15 to 16 years, and ADHD symptoms were measured using 2 different scales and different raters, from age 7 to 21 years, with effects tested using regression.ResultsA relative age effect emerged for English but not mathematics examination grades, and for the majority of parent and teacher ratings on ADHD symptoms, most consistently in middle childhood. Being young-in-class was associated with a greater reduction in parent-rated ADHD symptoms from childhood to adulthood when measured with a brief scale, but the comparable result from a longer scale was non-significant (after multiple testing correction). No interaction emerged between relative age and ADHD polygenic scores.ConclusionOur results emphasise the need to improve support for the children who start school younger than most, and to ensure that developmental comparisons take children’s precise age into account. Future research would benefit from in-depth analyses of individual trajectories and their variability among the young-in-class children.</div

Thermodynamic properties of the periodic Anderson model:X-boson treatment

We study the specific dependence of the periodic Anderson Model (PAM) in the limit of $U=\infty$ employing the X-boson treatment in two fifferent regimes of the PAM: the heavy fermion Kondo (HF-K) and the heavy fermion local magnetic regime (HF-LMM). We obtain a multiple peak structure for the specific heat in agreement with experimental results as well as the increase of the electronic effective mass at low temperatures associated with the HF-K regime. The entropy per site at low T tends to zero in the HF-K regime, corresponding to a singlet ground state, and it tends to $k_{B}ln(2)$ in the HF-LMM, corresponding to a doublet ground state at each site. The linear coefficient $\gamma(T)=C_{v}/T$ of the specific heat qualitatively agrees with the experimental results obtained for differents materials in the two regimes considered here.Comment: 9 pages, 14 figure

X-boson cumulant approach to the periodic Anderson model

The Periodic Anderson Model (PAM) can be studied in the infinite U limit by employing the Hubbard X operators to project out the unwanted states. We have already studied this problem employing the cumulant expansion with the hybridization as perturbation, but the probability conservation of the local states (completeness) is not usually satisfied when partial expansions like the Chain Approximation (CHA) are employed. Here we treat the problem by a technique inspired in the mean field approximation of Coleman's slave-bosons method, and we obtain a description that avoids the unwanted phase transition that appears in the mean-field slave-boson method both when the chemical potential is greater than the localized level Ef at low temperatures (T) and for all parameters at intermediate T.Comment: Submited to Physical Review B 14 pages, 17 eps figures inserted in the tex

Reconciling inflation with openness

It is already understood that the increasing observational evidence for an open Universe can be reconciled with inflation if our horizon is contained inside one single huge bubble nucleated during the inflationary phase transition. In this frame of ideas, we show here that the probability of living in a bubble with the right $\Omega_0$ (now the observations require $\Omega_0 \approx .2$) can be comparable with unity, rather than infinitesimally small. For this purpose we modify both quantitatively and qualitatively an intuitive toy model based upon fourth order gravity. As this scheme can be implemented in canonical General Relativity as well (although then the inflation driving potential must be designed entirely ad hoc), inferring from the observations that $\Omega_0 < 1$ not only does not conflict with the inflationary paradigm, but rather supports therein the occurrence of a primordial phase transition.Comment: 4 pages, one postscript figure, to be published on Physical Review D PACS: 98.80. C

Fano resonance in electronic transport through a quantum wire with a side-coupled quantum dot: X-boson treatment

The transport through a quantum wire with a side coupled quantum dot is studied. We use the X-boson treatment for the Anderson single impurity model in the limit of $U=\infty$. The conductance presents a minimum for values of T=0 in the crossover from mixed-valence to Kondo regime due to a destructive interference between the ballistic channel associated with the quantum wire and the quantum dot channel. We obtain the experimentally studied Fano behavior of the resonance. The conductance as a function of temperature exhibits a logarithmic and universal behavior, that agrees with recent experimental results.Comment: 6 pages, 10 eps figs., revtex

On Traversable Lorentzian Wormholes in the Vacuum Low Energy Effective String Theory in Einstein and Jordan Frames

Three new classes (II-IV) of solutions of the vacuum low energy effective string theory in four dimensions are derived. Wormhole solutions are investigated in those solutions including the class I case both in the Einstein and in the Jordan (string) frame. It turns out that, of the eight classes of solutions investigated (four in the Einstein frame and four in the corresponding string frame), massive Lorentzian traversable wormholes exist in five classes. Nontrivial massless limit exists only in class I Einstein frame solution while none at all exists in the string frame. An investigation of test scalar charge motion in the class I solution in the two frames is carried out by using the Plebanski-Sawicki theorem. A curious consequence is that the motion around the extremal zero (Keplerian) mass configuration leads, as a result of scalar-scalar interaction, to a new hypothetical "mass" that confines test scalar charges in bound orbits, but does not interact with neutral test particles.Comment: 18 page

Modeling the transition from decompensated to pathological hypertrophy

Background--Long-chain acyl-CoA synthetases (ACSL) catalyze the conversion of long-chain fatty acids to fatty acyl-CoAs. Cardiac-specific ACSL1 temporal knockout at 2 months results in a shift from FA oxidation toward glycolysis that promotes mTORC1-mediated ventricular hypertrophy. We used unbiased metabolomics and gene expression analyses to examine the early effects of genetic inactivation of fatty acid oxidation on cardiac metabolism, hypertrophy development, and function. Methods and Results--Global cardiac transcriptional analysis revealed differential expression of genes involved in cardiac metabolism, fibrosis, and hypertrophy development in Acsl1 H-/- hearts 2 weeks after Acsl1 ablation. Comparison of the 2- and 10-week transcriptional responses uncovered 137 genes whose expression was uniquely changed upon knockdown of cardiac ACSL1, including the distinct upregulation of fibrosis genes, a phenomenon not observed after complete ACSL1 knockout. Metabolomic analysis identified metabolites altered in hearts displaying partially reduced ACSL activity, and rapamycin treatment normalized the cardiac metabolomic fingerprint. Conclusions--Short-term cardiac-specific ACSL1 inactivation resulted in metabolic and transcriptional derangements distinct from those observed upon complete ACSL1 knockout, suggesting heart-specific mTOR (mechanistic target of rapamycin) signaling that occurs during the early stages of substrate switching. The hypertrophy observed with partial Acsl1 ablation occurs in the context of normal cardiac function and is reminiscent of a physiological process, making this a useful model to study the transition from physiological to pathological hypertrophy