2,052 research outputs found
Sphalerons and the Electroweak Phase Transition in Models with Higher Scalar Representations
In this work we investigate the sphaleron solution in a
gauge theory, which also encompasses the Standard Model, with higher scalar
representation(s) (). We show that the field profiles
describing the sphaleron in higher scalar multiplet, have similar trends like
the doublet case with respect to the radial distance. We compute the sphaleron
energy and find that it scales linearly with the vacuum expectation value of
the scalar field and its slope depends on the representation. We also
investigate the effect of gauge field and find that it is small for the
physical value of the mixing angle, and resembles the case for the
doublet. For higher representations, we show that the criterion for strong
first order phase transition, , is relaxed with respect to
the doublet case, i.e. .Comment: 20 pages, 5 figures & 1 table, published versio
Sharp conditions to avoid collisions in singular Cucker-Smale interactions
We consider the Cucker–Smale flocking model with a singular communication weight with . We provide a critical value of the exponent in the communication weight leading to global regularity of solutions or finite-time collision between particles. For , we show that there is no collision between particles in finite time if they are placed in different positions initially. For we investigate a version of the Cucker–Smale model with expanded singularity i.e. with weight , . For such model we provide a uniform with respect to the number of particles estimate that controls the -distance between particles. In case of it reduces to the estimate of collision avoidance
Comparing High Dimensional Word Embeddings Trained on Medical Text to Bag-of-Words For Predicting Medical Codes
Word embeddings are a useful tool for extracting knowledge from the free-form text contained in electronic health records, but it has become commonplace to train such word embeddings on data that do not accurately reflect how language is used in a healthcare context. We use prediction of medical codes as an example application to compare the accuracy of word embeddings trained on health corpora to those trained on more general collections of text. It is shown that both an increase in embedding dimensionality and an increase in the volume of health-related training data improves prediction accuracy. We also present a comparison to the traditional bag-of-words feature representation, demonstrating that in many cases, this conceptually simple method for representing text results in superior accuracy to that of word embeddings
Interface modification of clay and graphene platelets reinforced epoxy nanocomposites: a comparative study
The interface between the matrix phase and dispersed phase of a composite plays a critical role in influencing its properties. However, the intricate mecha-nisms of interface are not fully understood, and polymer nanocomposites are no exception. This study compares the fabrication, morphology, and mechanical and thermal properties of epoxy nanocomposites tuned by clay layers (denoted as m-clay) and graphene platelets (denoted as m-GP). It was found that a chemical modification, layer expansion and dispersion of filler within the epoxy matrix resulted in an improved interface between the filler mate-rial and epoxy matrix. This was confirmed by Fourier transform infrared spectroscopy and transmission electron microscope. The enhanced interface led to improved mechanical properties (i.e. stiffness modulus, fracture toughness) and higher glass transition temperatures (Tg) compared with neat epoxy. At 4 wt% m-GP, the critical strain energy release rate G1c of neat epoxy improved by 240 % from 179.1 to 608.6 J/m2 and Tg increased from 93.7 to 106.4 �C. In contrast to m-clay, which at 4 wt%, only improved the G1c by 45 % and Tg by 7.1 %. The higher level of improvement offered by m-GP is attributed to the strong interaction of graphene sheets with epoxy because the covalent bonds between the carbon atoms of graphene sheets are much stronger than silicon-based clay
On Global Flipped SU(5) GUTs in F-theory
We construct an SU(4) spectral divisor and its factorization of types (3,1)
and (2,2) based on the construction proposed in [1]. We calculate the chiral
spectra of flipped SU(5) GUTs by using the spectral divisor construction. The
results agree with those from the analysis of semi-local spectral covers. Our
computations provide an example for the validity of the spectral divisor
construction and suggest that the standard heterotic formulae are applicable to
the case of F-theory on an elliptically fibered Calabi-Yau fourfold with no
heterotic dual.Comment: 45 pages, 12 tables, 1 figure; typos corrected, footnotes added, and
a reference adde
Caffeine-induced synaptic potentiation in hippocampal CA2 neurons
Caffeine enhances cognition, but even high non-physiological doses have modest effects on synapses. A 1 adenosine receptors (A 1 Rs) are antagonized by caffeine and are most highly enriched in hippocampal CA2, which has not been studied in this context. We found that physiological doses of caffeine in vivo or A 1 R antagonists in vitro induced robust, long-lasting potentiation of synaptic transmission in rat CA2 without affecting other regions of the hippocampus
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Multiparticle azimuthal correlations for extracting event-by-event elliptic and triangular flow in Au + Au collisions at sNN =200 GeV
We present measurements of elliptic and triangular azimuthal anisotropy of charged particles detected at forward rapidity 1<|η|<3 in Au + Au collisions at sNN=200 GeV, as a function of centrality. The multiparticle cumulant technique is used to obtain the elliptic flow coefficients v2{2},v2{4},v2{6}, and v2{8}, and triangular flow coefficients v3{2} and v3{4}. Using the small-variance limit, we estimate the mean and variance of the event-by-event v2 distribution from v2{2} and v2{4}. In a complementary analysis, we also use a folding procedure to study the distributions of v2 and v3 directly, extracting both the mean and variance. Implications for initial geometrical fluctuations and their translation into the final-state momentum distributions are discussed
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Pseudorapidity Dependence of Particle Production and Elliptic Flow in Asymmetric Nuclear Collisions of p+Al, p+Au, d+Au, and ^{3}He+Au at sqrt[s_{NN}]=200 GeV.
Asymmetric nuclear collisions of p+Al, p+Au, d+Au, and ^{3}He+Au at sqrt[s_{NN}]=200 GeV provide an excellent laboratory for understanding particle production, as well as exploring interactions among these particles after their initial creation in the collision. We present measurements of charged hadron production dN_{ch}/dη in all such collision systems over a broad pseudorapidity range and as a function of collision multiplicity. A simple wounded quark model is remarkably successful at describing the full data set. We also measure the elliptic flow v_{2} over a similarly broad pseudorapidity range. These measurements provide key constraints on models of particle emission and their translation into flow
Flipped SU(5) GUTs from E_8 Singularities in F-theory
In this paper we construct supersymmetric flipped SU(5) GUTs from E_8
singularities in F-theory. We start from an SO(10) singularity unfolded from an
E_8 singularity by using an SU(4) spectral cover. To obtain realistic models,
we consider (3,1) and (2,2) factorizations of the SU(4) cover. After turning on
the massless U(1)_X gauge flux, we obtain the SU(5) X U(1)_X gauge group. Based
on the well-studied geometric backgrounds in the literature, we demonstrate
several models and discuss their phenomenology.Comment: 46 pages, 23 tables, 1 figure, typos corrected, references added, and
new examples presente
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