Quantum Gates to other Universes

We present a microscopic model of a bridge connecting two large Anti-de-Sitter Universes. The Universes admit a holographic description as three-dimensional ${\cal N}=4$ supersymmetric gauge theories based on large linear quivers, and the bridge is a small rank-$n$ gauge group that acts as a messenger. On the gravity side, the bridge is a piece of a highly-curved AdS$_5\times$S$_5$ throat carrying $n$ units of five-form flux. We derive a universal expression for the mixing of the two massless gravitons: $M^2 \simeq 3n^2 (\kappa_4^2 + \kappa_4^{\prime\,2})/16\pi^2$, where $M$ is the mass splitting of the gravitons, $\kappa_4^2, \kappa_4^{\prime\,2}$ are the effective gravitational couplings of the AdS$_4$ Universes, and $n$ is the quantized charge of the gate. This agrees with earlier results based on double-trace deformations, with the important difference that the effective coupling is here quantized. We argue that the apparent non-localities of holographic double-trace models are resolved by integrating-in the (scarce) degrees of freedom of the gate.Comment: 17 pages, 8 figures. Note added about an implicit assumption in the case of non-identical Universe

A worldsheet extension of O(d,d;Z)

We study superconformal interfaces between N=(1,1) supersymmetric sigma models on tori, which preserve a u(1)^{2d} current algebra. Their fusion is non-singular and, using parallel transport on CFT deformation space, it can be reduced to fusion of defect lines in a single torus model. We show that the latter is described by a semi-group extension of O(d,d;Q), and that (on the level of Ramond charges) fusion of interfaces agrees with composition of associated geometric integral transformations. This generalizes the well-known fact that T-duality can be geometrically represented by Fourier-Mukai transformations. Interestingly, we find that the topological interfaces between torus models form the same semi-group upon fusion. We argue that this semi-group of orbifold equivalences can be regarded as the \alpha' deformation of the continuous O(d,d) symmetry of classical supergravity.Comment: 71 pages, 1 figure, minor additions and correction

N=2 Moduli of AdS4 vacua: A fine-print study

We analyze the moduli spaces near N=4 supersymmetric AdS4 vacua of string theory by combining and comparing various approaches: (a) the known exact solutions of Type IIB string theory with localized 5-brane sourcees, (b) the holographically dual 3d quiver gauge theories; (c) gauged supergravity, and (d) the representations of the superconformal algebra Osp(4|4). Short multiplets containing the marginal N=2 deformations transform in the (2;0), (0;2) or (1;1) representations of the R-symmetry group SU(2)_H x SU(2)_C. The first two are classified by the chiral rings of the Higgs and Coulomb branches, while the latter contain mixed-branch operators. We identify the origin of these moduli in string theory, matching in particular the operators of the chiral rings with open strings on the magnetized 5-brane sources. Our results provide new evidence for the underlying holographic duality. The existence of a large number of bound-state moduli highlights the limitations of effective supergravity.Comment: 32 pages, 5 figures. Typos and some incorrect statements have been corrected which did not affect our analysi

Studies of the ATLAS Muon Spectrometer with Test Beam and Simulated Physics Data

In the ATLAS detector, muon related measurements are achieved by a huge Muon Spectrometer installed at the outermost region of the detector. At the LHC energies, high-pT muons are expected to be measured with a momentum resolution of â¼ 10% at 1 TeV . The main detecting element of the Muon Spectrometer is the Monitored Drift Tube chamber. The reconstruction potential of a BIS type Monitored Drift Tube chamber, in a special setup at the H8 Testbeam experimental area at CERN, is investigated. Data from the BIS muon chamber with both muon and positron beams are taken and the reconstruction of track segments in the chamber is studied. The correlation of the precision coordinate of the reconstructed track segment with the calorimeter cluster barycentre is also studied. In the ATLAS detector, muons lose parts of their energy in the Calorimetric System before reaching the Muon Spectrometer. As the muon energy increases radiative effects start playing a significant role in the energy loss mechanism and increase the probability for a big muon energy loss, often called as catastrophic. The probability for catastrophic energy losses of 350 GeV muons when they pass through the ATLAS calorimeters is studied with H8 testbeam data. Information on catastrophic muon energy losses in the calorimeters and also on the isolation of muons can be retrieved by a direct measurement of the calorimeter response. For this reason, a precise energ y deposition measurement method in the calorimeters is developed. The method enriches the muon object at the AOD anal- ysis level with information on calorimeter isolation and the collection of calorimeter cells associated with the measurement. The method is applied on single muon and t¯t â 4â + X events. Finally, the Z boson pair production through the process pp â ZZ(â) â ââââ, where â = e or â = μ is of great interest for the LHC physics searches because it constitutes the irreducible background to the observation of the Higgs boson production through the 4 lepton decay. The observation expectations of pp â ZZ â 4â channel with 1 fbâ1 of data is investigated and analysis methods on simulated events of signal and t¯t and Zb¯b backgrounds processes are described

On the Symmetries of Classical String Theory

I discuss some aspects of conformal defects and conformal interfaces in two spacetime dimensions. Special emphasis is placed on their role as spectrum-generating symmetries of classical string theory.Comment: Latex file, 12 pages, 1 figure. Contributed to the volume celebrating Claudio Bunster's sixtieth anniversary; based on talks at the Arnold Sommerfeld Workshop on "String Field Theory and Related Aspects", and for the 50th anniversary of the IHE

D-branes

This is an introduction to the non-perturbative excitations of string theory known as D-branes. Topics covered include their definition and main properties, their role in dualities and their dynamics. Based on lectures given at LACES 2019, and at the Amsterdam-Brussels-Geneva-Paris Doctoral School.Comment: 60 pages, 11 figures. Invited chapter for the Handbook of Quantum Gravity (Eds. C. Bambi, L. Modesto, and I. L. Shapiro, Springer 2023

Orientifolds of the 3-sphere

We study the geometry of orientifolds in the SU(2) WZW model. They correspond to the two inequivalent, orientation-reversing involutions of $S^3$, whose fixed-point sets are: the north and south poles (O0), or the equator two-sphere (O2). We show how the geometric action of these involutions leads unambiguously to the previously obtained algebraic results for the Klein bottle and Moebius amplitudes. We give a semiclassical derivation of the selection rules and signs in the crosscap couplings, paying particular attention to discrete B-fluxes. A novel observation, which does not follow from consistency of the one-loop vacuum diagrams, is that in the case of the O0 orientifolds only integer- or only half-integer-spin Cardy states may coexist.Comment: Latex file, 19 pages, one figure, uses JHEP.cls. One reference added, final version as it appeared in JHE

Unification with Low String Scale

I argue that in open-string theory with hierarchically small (or large) extra dimensions, gauge groups can unify naturally with logarithmically-running coupling constants at the high Kaluza-Klein (or string-winding) scale. This opens up the possibility of rescuing the standard logarithmic unification at $M_U\sim 10^{15-18}$ GeV even if the fundamental-string scale is much lower, at intermediate or possibly even electroweak scales. I also explain, however, why a low type-I string scale may not suffice to obliterate the ultraviolet problems usually associated with the gauge hierarchy.Comment: 6 pages, uses harvmac. Two minor changes. Final version to appear in JHE

(8,0) Quantum mechanics and symmetry enhancement in type I' superstrings

The low-energy supersymmetric quantum mechanics describing D-particles in the background of D8-branes and orientifold planes is analyzed in detail, including a careful discussion of Gauss' law and normal ordering of operators. This elucidates the mechanism that binds D-particles to an orientifold plane, in accordance with the predictions of heterotic/type I duality. The ocurrence of enhanced symmetries associated with massless bound states of a D-particle with one orientifold plane is illustrated by the enhancement of $SO(14) \times U(1)$ to $E_8$ and $SO(12)\times U(1)$ to $E_7$ at strong type I' coupling. Enhancement to higher-rank groups involves both orientifold planes. For example, the enhanced $E_8 \times E_8 \times SU(2)$ symmetry at the self-dual radius of the heterotic string is seen as the result of two D8-branes coinciding midway between the orientifold planes, while the enhanced $SU(18)$ symmetry results from the coincidence of all sixteen D8-branes and $SO(34)$ when they also coincide with an orientifold plane. As a separate by-product, the s-rule of brane-engineered gauge theories is derived by relating it through a chain of dualities to the Pauli exclusion principle.Comment: 30 pages LaTeX, Five figures. Two references added as well as some Comments in section4. v4: Missing backslashes added to four reference citations