From the Sakai-Sugimoto Model to the Generalized Skyrme Model

We derive the generalized Skyrme model as a low-energy effective model of the Sakai-Sugimoto model. The novelty with the past is the presence of the sextic term equal to the topological charge squared. This term appears when the $\omega$ meson, and the tower of states on top of it, are integrated out. We claim that, in the small 't Hooft coupling limit, the instanton is well described by a Skyrmion arising from the low energy effective Lagrangian of the Sakai-Sugimoto model. The sextic term plays a dominant role in this limit. Moreover, when a pion mass term is added we recover the BPS Skyrme model in the small 't Hooft coupling limit.Comment: 17 pages, 6 figures. v2: minor correction

Detailed Analysis of The Pull-Up Exercise

The pull-up exercise has been used as a performance measure to assess physical fitness and muscular strength and endurance of the major muscles in the upper limb. The ability to successfully perform multiple repetitions of a pull-up is dependent upon a performer’s body mass, muscle strength, and movement style.https://digitalcommons.gardner-webb.edu/exercise-science-research-proposal-posters/1177/thumbnail.jp

Neutron electric dipole moment from gauge/string duality

We compute the electric dipole moment of nucleons in the large $N_c$ QCD model by Witten, Sakai and Sugimoto with $N_f=2$ degenerate massive flavors. Baryons in the model are instantonic solitons of an effective five-dimensional action describing the whole tower of mesonic fields. We find that the dipole electromagnetic form factor of the nucleons, induced by a finite topological $\theta$ angle, exhibits complete vector meson dominance. We are able to evaluate the contribution of each vector meson to the final result - a small number of modes are relevant to obtain an accurate estimate. Extrapolating the model parameters to real QCD data, the neutron electric dipole moment is evaluated to be $d_n = 1.8 \cdot 10^{-16}\, \theta\;e\cdot \mathrm{cm}$. The electric dipole moment of the proton is exactly the opposite.Comment: Latex, 4 pages; v2: minor corrections, few comments adde

Symmetry energy in holographic QCD

We study the symmetry energy, an important quantity in nuclear physics, in the Witten-Sakai-Sugimoto model and in a much simpler hard-wall model of holographic QCD. The symmetry energy corresponds to the energy increase in going from a nucleus with equal number of neutrons and protons to one with the same number of nucleons but with one neutron or one proton more. Using a homogeneous Ansatz representing smeared instantons and quantizing their isospin quantum numbers, we extract the symmetry energy as well as the proton fraction under the assumption of charge neutrality and beta-equilibrium. We find that the symmetry energy can be well described in our models if we allow for a somewhat larger 't Hooft coupling than is normally used in phenomenological fits, passing all experimental constraints and is compatible with results from nuclear physics at low densities.Comment: REVTeX: 7 pages, 3 figure

Neutron stars in the Witten-Sakai-Sugimoto model

We utilize the top-down holographic QCD model, the Witten-Sakai-Sugimoto model, in a hybrid setting with the SLy4 equation of state to describe neutron stars with high precision. In particular, we employ a calibration that bootstraps the nuclear matter by fitting the Kaluza-Klein scale and the 't Hooft coupling such that the physical saturation density and physical symmetry energy are achieved. We obtain static stable neutron star mass-radius data via the Tolman-Oppenheimer-Volkov equations that yield sufficiently large maximal masses of neutron stars to be compatible with the recently observed PSR-J0952-0607 data as well as all other known radius and tidal deformation constraints.Comment: LaTeX: 18 pages, 6 figure

Boundary terms in the Witten-Sakai-Sugimoto model at finite density

We consider the Witten-Sakai-Sugimoto model in the approximation of smeared instantons at finite density via a homogeneous Ansatz, which is known to be discontinuous in order to be able to contain a nonvanishing baryon density. The discontinuity at the infrared tip of the bulk spacetime gives rise to subtleties of discarding boundary terms that are normally discarded in the literature. We propose a reason for discarding this boundary term, by scrutinizing the currents and topological properties of the model. Along the way, we find a very effective and simple condition to compute the point of thermodynamic equilibrium.Comment: LaTeX: 28 pages, 4 figure

NYCTEREUTES (MAMMALIA, CARNIVORA, CANIDAE) FROM LAYNA AND THE EURASIAN RACCOON-DOGS: AN UPDATED REVISION

The Early Pliocene site of Layna (MN15, ca 3.9 Ma) is renowned for its record of several mammalian taxa, among which the raccoon-dog Nyctereutes donnezani. Since the early description of this sample, new fossils of raccoon-dogs have been discovered, including a nearly complete cranium. The analysis and revision here proposed, with new diagnoses for the identified taxa, confirm the attribution of the majority of the material to the primitive taxon N. donnezani, enriching and clarifying our knowledge of the cranial and postcranial morphological variability of this species. Nevertheless, the analysis also reveals the presence in Layna of some specimens with strong morphological affinity to the derived N. megamastoides. The occurrence of such a derived taxon in a rather old site, has critical implications for the evolutionary history and dispersal pattern of these small canids. For instance, it reconciles the Western European and Asian records. Formerly, it was commonly thought that the evolutionary pattern of Early Pliocene raccoon-dogs in Europe was substantially different from the Asian one, where the advanced N. sinensis and the primitive N. tingi apparently coexisted in the same sites ; conversely, Europe was characterized by the occurrence of the single species N. donnezani. Our recognition of a derived taxon in the MN15 zone suggests the existence of similar ecological dynamics at the two extremes of the paleobiogeographic range of the genus (i.e., across the entire Eurasia). &nbsp

Assessing the scientific value and vulnerability of paleontological sites: a new analytic operational procedure

Introduction: Paleontological heritage rarely receives the same legislative attention as archeological heritage. Part of the problem seems to be, at least in some contexts (e.g., Italy), the difficulty of acknowledging fossils as distinct assets from other cultural heritage objects and the lack of expertise among the administrative functionaries. This study aims to describe and test an objective analytic operational procedure that could allow for the assessment of the relevance of any fossiliferous site and its potential vulnerability in its present state. Methods: The estimations were obtained using several quantitative and qualitative parameters that could describe the probability of fossil recovery for each site (Pr) and the scientific and cultural interest of the locality (In). Each parameter has subcategories for better defining. The product of probability and interest results in the scientific value (S), generally expressed as a percentage (S*). The vulnerability index (V) of productive and active sites considers the use of the land (U) and the natural erosion (E). The parameters were thought to apply to any type of fossil locality. We tested the indexes on 22 localities (7 of which were with paleoichnological records and 15 with direct body-fossil evidence), all different from one another. Results: The results show that the proposed indexes well describe and characterize each locality. Most of the sites are moderately vulnerable (V between 1 and 3) except for large quarry sites (e.g., Pirro Nord, Italy and Solnhofen, Germany) whose vulnerability indexes fell in the maximum degree of risk. Discussion: The operational procedure presented here is a simple, objective, and remotely applicable method allowing paleontologists and non-expert personnel to categorize localities and, therefore, act as a base to plan actions in paleontological heritage management relative to territorial development and land use