Canonical density matrix perturbation theory

Density matrix perturbation theory [Niklasson and Challacombe, Phys. Rev. Lett. 92, 193001 (2004)] is generalized to canonical (NVT) free energy ensembles in tight-binding, Hartree-Fock or Kohn-Sham density functional theory. The canonical density matrix perturbation theory can be used to calculate temperature dependent response properties from the coupled perturbed self-consistent field equations as in density functional perturbation theory. The method is well suited to take advantage of sparse matrix algebra to achieve linear scaling complexity in the computational cost as a function of system size for sufficiently large non-metallic materials and metals at high temperatures.Comment: 21 pages, 3 figure

Hadron Masses and Screening from AdS Wilson Loops

We show that in strongly coupled N=4 SYM the binding energy of a heavy and a light quark is independent of the strength of the coupling constant. As a consequence we are able to show that in the presence of light quarks the analog of the QCD string can snap and color charges are screened. The resulting neutral mesons interact with each other only via pion exchange and we estimate the massesComment: 4 pages, revte

Tensors Mesons in AdS/QCD

We explore tensor mesons in AdS/QCD focusing on f2 (1270), the lightest spin-two resonance in QCD. We find that the f2 mass and the partial width for f2 -> gamma gamma are in very good agreement with data. In fact, the dimensionless ratio of these two quantities comes out within the current experimental bound. The result for this ratio depends only on Nc and Nf, and the quark and glueball content of the operator responsible for the f2; more importantly, it does not depend on chiral symmetry breaking and so is both independent of much of the arbitrariness of AdS/QCD and completely out of reach of chiral perturbation theory. For comparison, we also explore f2 -> pi pi, which because of its sensitivity to the UV corrections has much more uncertainty. We also calculate the masses of the higher spin resonances on the Regge trajectory of the f2, and find they compare favorably with experiment.Comment: 21 pages, 1 figure; Li's correcte

A Non-Renormalization Theorem for the d=1, N=8 Vector Multiplet

Sigma models describing low energy effective actions on D0-brane probes with N=8 supercharges are studied in detail using a manifestly d=1, N=4 super-space formalism. Two 0+1 dimensional N=4 multiplets together with their general actions are constructed. We derive the condition for these actions to be N=8 supersymmetric and apply these techniques to various D-brane configurations. We find that if in addition to N=8 supersymmetry the action must also have Spin(5) invariance, the form of the sigma model metric is uniquely determined by the one-loop result and is not renormalized perturbatively or non-perturbatively.Comment: Uses harvmac, 16 pages. We correct an error pointed out by E. Witte

Scoping the potencial for outdoor microalgae production in the Azores

Microalgae cultivation has received much attention due to some desirable characteristics such as fast growth rates, high photosynthetic efficiencies and the production of valuable biochemicals. Mass cultivation of microalgae for commercial purposes is already a reality in some locations being an activity with approximately 45 years. The Azores archipelago, located in the North Atlantic Ocean off the coast of Portugal, features a temperate climate. To evaluate the feasibility of local outdoor microalgae production, certain fundamental factors must be analysed. In this study water, light, temperature, carbon sources, nutrients, international outlook and regional context were analyzed from the perspective of a local outdoor commercial microalgae production. A SWOT analysis was applied to the analysed factors to evaluate the strengths, weaknesses, opportunities and threats. The results nominate the Azores as a promising location to implement an outdoor production of valueadded products from microalgae.Oma – Observatório do Mar dos Açores ; MARE – Centro de Ciências do Mar e do Ambiente ; IMAR – Instituto do Mar ; DOP – Departamento de Oceanografia e Pescas ; Universidade dos Açoresinfo:eu-repo/semantics/publishedVersio

The Littlest Higgs

We present an economical theory of natural electroweak symmetry breaking, generalizing an approach based on deconstruction. This theory is the smallest extension of the Standard Model to date that stabilizes the electroweak scale with a naturally light Higgs and weakly coupled new physics at TeV energies. The Higgs is one of a set of pseudo Goldstone bosons in an $SU(5)/SO(5)$ nonlinear sigma model. The symmetry breaking scale $f$ is around a TeV, with the cutoff \Lambda \lsim 4\pi f \sim 10 TeV. A single electroweak doublet, the ``little Higgs'', is automatically much lighter than the other pseudo Goldstone bosons. The quartic self-coupling for the little Higgs is generated by the gauge and Yukawa interactions with a natural size $O(g^2,\lambda_t^2)$, while the top Yukawa coupling generates a negative mass squared triggering electroweak symmetry breaking. Beneath the TeV scale the effective theory is simply the minimal Standard Model. The new particle content at TeV energies consists of one set of spin one bosons with the same quantum numbers as the electroweak gauge bosons, an electroweak singlet quark with charge 2/3, and an electroweak triplet scalar. One loop quadratically divergent corrections to the Higgs mass are cancelled by interactions with these additional particles.Comment: 15 pages. References added. Corrected typos in the discussion of the top Yukawa couplin

Charge and spin criticality for the continuous Mott transition in a two-dimensional organic conductor

We study the continuous bandwidth-controlled Mott transition in the two-dimensional single-band Hubbard model with a focus on the critical scaling behavior of charge and spin degrees of freedom. Using plaquette cluster dynamical mean-field theory, we find charge and spin criticality consistent with experimental results for organic conductors. In particular, the charge degree of freedom measured via the local density of states at the Fermi level shows a smoother transition than expected for the Ising universality class and in single-site dynamical mean-field theory, revealing the importance of short-ranged nonlocal correlations in two spatial dimensions. The spin criticality measured via the local spin susceptibility agrees quantitatively with nuclear magnetic resonance measurements of the spin-lattice relaxation rate.Comment: 5 pages, 2 figure