D3-branes dynamics and black holes

Using the D3-brane as the fundamental tool, we adress two aspects of D-branes physics. The first regards the interaction between two electromagnetic dual D-branes in 10 dimensions. In particular, we give a meaning to {\it both} even and odd spin structure contributions, the latter being non vanishing for non zero relative velocity $v$ (and encoding the Lorentz-like contribution). The second aspect regards the D-brane/black holes correspondence. We show how the 4 dimensional configuration corresponding to a {\it single} D3-brane wrapped on the orbifold T^6/Z_3 represents a regular Reissner-Nordstrom solution of d=4 N=2 supergravityComment: 8 pages, latex, 1 eps figure. Talk presented by M. Bertolini at the conference "Quantum aspects of gauge theories, supergravity and unification" in Corfu`; to appear in the proceeding

N=1 Super QCD and Fractional Branes

We show how to get the one-loop beta function and the chiral anomaly of N=1 Super QCD from a stack of fractional N D3-branes localized inside the world-volume of 2M fractional D7-branes on the orbifold C^3/(Z_2 x Z_2). They are obtained by analyzing the classical supergravity background generated by such a brane configuration, in the spirit of the gauge/gravity correspondence.Comment: 4 pages, LaTeX. Talk given at the IXth International Symposium on Particles, Strings and Cosmology PASCOS '03, Mumbai-India, January 3-8 2003. To appear in a special issue of Praman

Supersymmetry breaking at the end of a cascade of Seiberg dualities

We study the IR dynamics of the cascading non-conformal quiver theory on N regular and M fractional D3 branes at the tip of the complex cone over the first del Pezzo surface. The horizon of this cone is the irregular Sasaki-Einstein manifold Y^{2,1}. Our analysis shows that at the end of the cascade supersymmetry is dynamically broken.Comment: 12 pages, 2 figures, minor changes, typos correcte

Higgs Limit and b->s gamma Constraints in Minimal Supersymmetry

New limits on the Higgs mass from LEP and new calculations on the radiative (penguin) decay of the b->s gamma branching ratio restrict the parameter space of the Constrained Minimal Supersymmetric Standard Model (CMSSM). We find that for the low tan(beta) scenario only one sign of the Higgs mixing parameter is allowed, while the high tan(beta scenario is practically excluded, if one requires all sparticles to be below 1 TeV and imposes radiative electroweak symmetry breaking as well as gauge and Yukawa coupling unification. For squarks between 1 and 2 TeV high tan(beta) scenarios are allowed. We consider especially a new high tan(beta)=64 scenario with triple unification of all Yukawa couplings of the third generation, which show an infrared fixed point behaviour. The upper limit on the mass of the lightest Higgs in the low (high) tan(beta) scenarios is 97+-6~(120+-2) GeV, where the errors originate predominantly from the uncertainty in the top mass.Comment: latex + 6 eps figs, 10 pages, IEKP-KA/98-08; References updated in replacement + 1 figure concerning triple Yukawa unification added for final publication in Phys. Let

Soft Functions for Generic Jet Algorithms and Observables at Hadron Colliders

We introduce a method to compute one-loop soft functions for exclusive $N$-jet processes at hadron colliders, allowing for different definitions of the algorithm that determines the jet regions and of the measurements in those regions. In particular, we generalize the $N$-jettiness hemisphere decomposition of [Jouttenus 2011] in a manner that separates the dependence on the jet boundary from the observables measured inside the jet and beam regions. Results are given for several factorizable jet definitions, including anti-$k_T$, XCone, and other geometric partitionings. We calculate explicitly the soft functions for angularity measurements, including jet mass and jet broadening, in $pp \to L + 1$ jet and explore the differences for various jet vetoes and algorithms. This includes a consistent treatment of rapidity divergences when applicable. We also compute analytic results for these soft functions in an expansion for a small jet radius $R$. We find that the small-$R$ results, including corrections up to $\mathcal{O}(R^2)$, accurately capture the full behavior over a large range of $R$.Comment: 33 pages + appendices, 17 figures, v2: journal version, v3: fixed typo in eq.(4.37

New physics in \epsilon' from chromomagnetic contributions and limits on Left-Right symmetry

New physics in the chromomagnetic flavor changing transition s->dg* can avoid the strong GIM suppression of the Standard Model and lead to large contributions to CP-violating observables, in particular to the epsilon' parameter, that we address here. We discuss the case of the Left-Right symmetric models, where this contribution implies bounds on the phases of the right-handed quark mixing matrix, or in generic models with large phases a strong bound on the Left-Right symmetry scale. To the leading order, a numeric formula for epsilon' as a function of the short-distance coefficients for a wide class of models of new physics is given.Comment: 12 pages, Eq. 12 and related numerics amende

Microphotoluminescence study of disorder in ferromagnetic (Cd,Mn)Te quantum well

Microphotoluminescence mapping experiments were performed on a modulation doped (Cd,Mn)Te quantum well exhibiting carrier induced ferromagnetism. The zero field splitting that reveals the presence of a spontaneous magnetization in the low-temperature phase, is measured locally; its fluctuations are compared to those of the spin content and of the carrier density, also measured spectroscopically in the same run. We show that the fluctuations of the carrier density are the main mechanism responsible for the fluctuations of the spontaneous magnetization in the ferromagnetic phase, while those of the Mn spin density have no detectable effect at this scale of observation.Comment: 4 pages, 3 figure

p-Type doping of II-VI heterostructures from surface states: application to ferromagnetic Cd1−x_{1-x}Mnx_xTe quantum wells

We present a study of p-type doping of CdTe and Cd$_{1-x}$Mn$_x$Te quantum wells from surface states. We show that this method is as efficient as usual modulation doping with nitrogen acceptors, and leads to hole densities exceeding $2 \times 10^{11}$ cm$^{-2}$. Surface doping was successfully applied to obtain carrier-induced ferromagnetism in a Cd$_{1-x}$Mn$_x$Te quantum well. The observed temperature dependence of photoluminescence spectra, and the critical temperature, correspond well to those previously reported for ferromagnetic quantum wells doped with nitrogen.Comment: 4 figure

Gauge/Gravity Correspondence from Open/Closed String Duality

We compute the annulus diagram corresponding to the interaction of a fractional D3 brane with a gauge field on its world-volume and a stack of N fractional D3 branes on the orbifolds C^2 /Z_2 and C^3/Z_2 x Z_2. We show that its logarithmic divergence can be equivalently understood as due either to massless open string states circulating in the loop or to massless closed string states exchanged between two boundary states. This follows from the fact that, under open/closed string duality, massless states in the open and closed string channels are matched into each other without mixing with massive states. This explains why the perturbative properties of many gauge theories living on the worldvolume of less supersymmetric and nonconformal branes have been recently obtained from their corresponding supergravity solution.Comment: LaTeX, 28 page