Search

Recently there has been interest in electroweak models on a five dimensional interval that break the symmetry without a higgs boson. By warping the metric of the interval it may be possible to avoid experimental bounds on extra W bosons and delta rho. Five dimensional models necessarily require an explicit UV cut-off to remain perturbative, such as that provided by deconstruction. We study a simple deconstruction of this scenario with a chain of SU(2)^N+1 x U(1)_Y groups linked by bi-fundamental higgs. There are two interesting decoupling limits of this model, when the higgs vevs are taken large and when the SU(2) couplings grow, which might provide a perturbative realization. In fact it is very challenging to satisfy all the experimental bounds and the most compatible scenario has both a higgs and a relatively strongly coupled new W both close to 2 TeV, Comment: 10 pages, 6 figures, additional discussion

We study the low energy dynamics of pions in a gravity dual of chiral symmetry breaking. The string theory construction consists of a probe D7 brane in the Constable Myers non-supersymmetric background, which has been shown to describe chiral symmetry breaking in the pattern of QCD. We expand the D7 brane's Dirac Born Infeld action for fluctuations that correspond to the Goldstone mode and show that they take the form of a non-linear chiral lagrangian. We numerically compute the quark condensate, pion decay constant and higher order Gasser Leutwyler coefficients. We find their form is consistent with naive dimensional analysis estimates. We also explore the gauging of the quark's chiral symmetries and the vector meson spectrum., Comment: 24 pages, LaTeX, 7 figures

We study aspects of confinement in two deformed versions of the AdS/CFT correspondence - the GPPZ dual of N=1* Yang Mills, and the Yang Mills* N=0 dual. Both geometries describe discrete glueball spectra which we calculate numerically. The results agree at the 10% level with previous AdS/CFT computations in the Klebanov Strassler background and AdS Schwarzchild respectively. We also calculate the spectra of bound states of the massive fermions in these geometries and show that they are light, so not decoupled from the dynamics. We then study the behaviour of Wilson loops in the 10d lifts of these geometries. We find a transition from AdS-like strings in the UV to strings that interact with the unknown physics of the central singularity of the space in the IR., Comment: latex, 24 pages, 7 figures, extra analysis and interpretation of Wilson loops

We describe a ten dimensional supergravity geometry which is dual to a gauge theory that is non-supersymmetric Yang Mills in the infra-red but reverts to $N$=4 super Yang Mills in the ultra-violet. A brane probe of the geometry shows that the scalar potential of the gauge theory is stable. We discuss the infra-red behaviour of the solution. The geometry describes a Schroedinger equation potential that determines the glueball spectrum of the theory; there is a mass gap and a discrete spectrum. The glueball mass predictions match previous AdS/CFT Correspondence computations in the non-supersymmetric Yang Mills theory, and lattice data, at the 10% level. (Based on a talk presented at SCGT02 in Nagoya, Japan), Comment: 8 pages, 2 figures

We study non-supersymmetric fermion mass and condensate deformations of the AdS/CFT Correspondence. The 5 dimensional supergravity flows are lifted to a complete and remarkably simple 10 dimensional background. A brane probe analysis shows that when all the fermions have an equal mass a positive mass is generated for all six scalar fields leaving non-supersymmetric Yang Mills theory in the deep infra-red. We numerically determine the potential, produced by the background, in the Schroedinger equation relevant to the study of O^++ glueballs. The potential is a bounded well, providing evidence of stability and for a discrete, confined spectrum. The geometry can also describe the supergravity background around an (unstable) fuzzy 5-brane., Comment: 20 pages, 3 figures

We deform the AdS/CFT Correspondence by the inclusion of a non-supersymmetric scalar mass operator. We discuss the behaviour of the dual 5 dimensional supergravity field then lift the full solution to 10 dimensions. Brane probing the resulting background reveals a potential consistent with the operator we wished to insert., Comment: 11 pages, 2 figures

We study N=4 super Yang Mills theory at finite U(1)_R charge density (and temperature) using the AdS/CFT Correspondence. The ten dimensional backgrounds around spinning D3 brane configurations split into two classes of solution. One class describe spinning black holes and have previously been extensively studied, and interpreted, in a thermodynamic context, as the deconfined high density phase of the dual field theory. The other class have naked singularities and in the supersymmetric limit are known to correspond to multi-centre solutions describing the field theory in the Coulomb phase. We provide evidence that the non-supersymmetric members of this class represent naked, spinning D-brane distributions describing the Coulomb branch at finite density. At a critical density a phase transition occurs to a spinning black hole representing the deconfined phase where the higgs vevs have evaporated. We perform a free energy calculation to determine the phase diagram of the Coulomb branch at finite temperature and density., Comment: 12 pages, 3 eps figures, minor corrections

Recently a new class of composite Higgs models have been developed which give rise to naturally light Higgs bosons without supersymmetry. Based on the chiral symmetries of ``theory space,'' involving replicated gauge groups and appropriate gauge symmetry breaking patterns, these models allow the scale of the underlying strong dynamics giving rise to the composite particles to be as large as of order 10 TeV, without any fine tuning to prevent large corrections to Higgs boson mass(es) of order 100 GeV. In this note we show that the size of flavor violating interactions arising generically from underlying flavor dynamics constrain the scale of the Higgs boson compositeness to be greater than of order 75 TeV, implying that significant fine-tuning is required. Without fine-tuning, the low-energy structure of the composite Higgs model alone is not sufficient to eliminate potential problems with flavor-changing neutral currents or excessive CP violation; solving those problems requires additional information or assumptions about the symmetries of the underlying flavor or strong dynamics. We also consider the weaker, but more model-independent, bounds which arise from limits on weak isospin violation., Comment: 12 pages, two eps figures included. Minor revisions and added references

We study the addition of an irrelevant operator to the N=4 supersymmetric large n SU(n) gauge theory, in the presence of finite temperature, T. In the supergravity dual, the effect of the operator is known to correspond to a deformation of the AdS_5 x S^5 ``throat'' which restores the asymptotic ten dimensional Minkowski region of spacetime, completing the full D3-brane solution. The system at non-zero T is interesting, since at the extremes of some of the geometrical parameters the geometry interpolates between a seven dimensional spherical Minkowskian Schwarzschild black hole (times R^3) and a five dimensional flat AdS Schwarzschild black hole (times S^5). We observe that when the coupling of the operator reaches a critical value, the deconfined phase, which is represented by the geometry with horizon, disappears for all temperatures, returning the system to a confined phase which is represented by the thermalised extremal geometry., Comment: 17 pages, 5 eps figures, LaTeX, added discussion and refs

We investigate supergravity solutions describing D5 branes wrapped on a two cycle which are dual to N=2 super Yang Mills theory. Brane probing these solutions allows the moduli space of the field theory to be identified. There are a unique set of coordinates in which the field theory on the probe takes an N=2 form and in these coordinates the running coupling of the gauge theory may be identified. We show that the geometry, when restricted to the moduli space, takes a very simple form involving only two functions. One is the running gauge coupling whilst the other parametrizes the scalar operators of the field theory. The D5 brane distributions, for the full set of solutions in the literature,can be determined by assuming the field theory's form for the running coupling as a function of scalar vevs. We show that the resulting distributions also correctly reproduce the scalar operators parametrized elsewhere providing the first non-trivial consistency check on the duality., Comment: 11 pages

A chemical potential may be introduced into the AdS/CFT correspondence by setting the D3 branes of the construction spinning. In the field theory the fermionic modes are expected to condense as Cooper pairs, although at zero temperature the chemical potential destabilizes the scalar sector of the N=4 theory obscuring this phenomena. We show, in the case where a chemical potential is introduced for a small number of the gauge colours, that there is a metastable vacuum for the scalar fields where fermionic Cooper pairing is apparently manifest. In this vacuum the D3 branes expand non-commutatively (to balance the centrifugal force) into a D5 brane, in a mechanism analogous to Harmark and Savvidy's (M)atrix theory construction of a spinning D2 brane. We show that the D5 brane acts as a source for the RR 3-form whose UV scaling and symmetries are those of a fermion bilinear. The D5 brane rotates within the S^5 and so decays by the emission of RR fields which we interpret as the metastable vacuum decaying via higher dimension operators., Comment: 12 pages (minor corrections)

The metric of the gravity dual of a field theory should contain precisely the same information as the field theory. We discuss this connection in the N=4 theory where a scalar vev may be introducedat the level of 5d supergravity and the solutions lifted to 10d. We stress the role of brane probing in finding the coordinates appropriate to the field theory. In these coordinates the metric parametrizes the gauge invariant operators of the field theory and either side of the duality is uniquely determined by the other. We follow this same chain of computations for the 10d lift of the N=2* geometry of Pilch and Warner. The brane probe of the metric reveals the 2d moduli space and the functional form of the gauge coupling. In the coordinates appropriate to the field theory the metric on moduli space takes a very simple form and one can read off the gravity predictions for operators in the field theory. Surprisingly there is logarithmic renormalization even in the far UV where the field theory reverts to N=4 super Yang-Mills. We extend the analysis of Buchel et al to find the D3 brane source distribution that generates the supergravity prediction for the gauge coupling for the whole class of solutions corresponding to different points on moduli space. This distribution does not account for the logarithmic behaviour in the rest of the metric though. We discuss possible resolutions of the discrepancy., Comment: 16 pages, references updated

In the AdS/CFT correspondence motion in the radial direction of the AdS space is identified with renormalization group flow in the field theory. For the N=4 Yang-Mills theory this motion is trivial. More interesting examples of renormalization group flow occur when the N=4 theory is deformed. Aspects of the flows are discussed for the N=4 theory on its moduli space, and deformed to N=2 in the infra-red within the context of 5d SUGRA. 10d lifts and brane probing are crucial tools for linking the spacetime backgrounds to the dual field theory., Comment: 7 pages, 2 fig, presented at the 2nd Conference on the Exact RG, Rome 2000, refs added

We study the family of ten dimensional type IIB supergravity solutions corresponding to renormalisation group flows from N=4 to N=2 supersymmetric Yang-Mills theory. Part of the solution set corresponds to a submanifold of the Coulomb branch of the gauge theory, and we use a D3-brane probe to uncover details of this physics. At generic places where supergravity is singular, the smooth physics of the probe yields the correct one-loop form of the effective low energy gauge coupling. The probe becomes tensionless on a ring at finite radius. Supergravity flows which end on this ``enhancon'' ring correspond to the vacua where extra massless degrees of freedom appear in the gauge theory, and the gauge coupling diverges there. We identify an SL(2,Z) duality action on the enhancon ring which relates the special vacua, and comment on the massless dyons within them. We propose that the supergravity solution inside the enhancon ring should be excised, since the probe's tension is unphysical there., Comment: 25 pages, 3 composite figures, LaTex (v2: reference added. clarifying footnote added. typos corrected, with addition to discussion of BPS dyons in section 7.)

We investigate collider signals for gauged flavor symmetries that have been proposed in models of dynamical electroweak symmetry breaking and fermion mass generation. We consider the limits on the masses of the gauge bosons in these models which can be extracted from Tevatron Run I data in dijet production. Estimates of the Run II search potential are provided. We show that the models also give rise to significant signals in single top production which may be visible at Run II. In particular we study chiral quark family symmetry and SU(9) chiral flavor symmetry. The Run I limits on the gauge bosons in these models lie between (1.5-2) TeV and should increase to about 3 TeV in Run II. Finally, we show that an SU(12) enlargement of the SU(9) model, including leptonic interactions, is constrained by low energy atomic parity violation experiments to lie outside the reach of the Tevatron., Comment: 22 pages, 4 ps figures

Precision electroweak data are generally believed to constrain the Higgs boson mass to lie below approximately 190 GeV at 95% confidence level. The standard Higgs model is, however, trivial and can only be an effective field theory valid below some high energy scale characteristic of the underlying non-trivial physics. Corrections to the custodial isospin violating parameter T arising from interactions at this higher energy scale dramatically enlarge the allowed range of Higgs mass. We perform a fit to precision electroweak data and determine the region in the (m_H, Delta T) plane that is consistent with experimental results. Overlaying the estimated size of corrections to T arising from the underlying dynamics, we find that a Higgs mass up to 500 GeV is allowed. We review two composite Higgs models which can realize the possibility of a phenomenologically acceptable heavy Higgs boson. We comment on the potential of improvements in the measurements of m_t and M_W to improve constraints on composite Higgs models., Comment: 9 pages, 2 eps figures. Shortened for PRL; some references elminated

The modern precision accelerator data has essentially ruled out the most obvious model of dynamical electroweak symmetry breaking, technicolour. The idea is though well motivated and it is important to construct models compatible with the precision data of this ilk to motivate experimental searches. We describe the top-see-saw and flavour universal symmetry breaking models that break electroweak symmetry dynamically yet have a decoupling limit for all new physics. Limits on the scale of such new physics may be placed using precision data and direct search results from the Tevatron., Comment: 10 pages, LaTeX, 2 eps figures, To appear in the Proceedings of Beyond the Desert99: Accelerator, Non-Accelerator and Space Approaches}, Castle Ringberg, Tegernsee, Germany, June 6-12 1999

We investigate the possible ground states of QCD at asymptotic densities, where the theory is expected to exhibit color superconductivity. We characterize the color-flavor structure of possible diquark condensates, and find those that are energy extrema by solving the weak-coupling Dyson-Schwinger equations, including Landau damping and the Meissner effect. We show that, as previously anticipated, in the two flavor case the vacuum breaks SU(3) color to SU(2) and in the three flavor case the vacua with color-flavor locking (CFL) have the lowest energy. We identify a number of relatively flat directions in the potential along which the pattern of gauge symmetry breaking changes and parity is violated. We discuss possible phenomenological consequences of our results., Comment: 16 pages, LaTeX, 6 postscript figures

The triviality of the scalar sector of the standard one-doublet Higgs model implies that this model is only an effective low-energy theory valid below some cut-off scale Lambda. For a heavy higgs this scale must be relatively low (10 TeV or less). Additional interactions coming from the underlying theory, and suppressed by the scale Lambda, give rise to model-dependent corrections to precisely measured electroweak quantities. Dimension six operators arising from the underlying physics naturally contribute to the S and T parameters, and their effects should be included in a global fit to the precision data that determines any limit on the Higgs mass. Using dimensional analysis, we estimate the expected size of these corrections in a custodially-symmetric strongly-interacting underlying theory. Taking these operators' coefficients to be of natural size gives sufficiently large contributions to the T parameter to reconcile Higgs masses as large as 400-500 GeV with the precision data., Comment: 9 pages, 3 epsf figures included

Gauged flavor symmetries at low energies have been proposed in models of dynamical electroweak symmetry breaking and fermion mass generation. The massive flavor gauge bosons give rise to corrections to precisely measured electroweak quantities. We perform a fit to collider electroweak data and place indirect limits on such new physics. In particular we study several models from the literature: universal coloron; chiral top color; chiral, quark family symmetry; SU(9) and SU(12) chiral, flavor symmetry. The 95% exclusion limits on the mass of the heavy gauge bosons for these models, at their critical coupling for chiral symmetry breaking, typically lie between 1-3 TeV. We discuss the robustness of these bounds with respect to changes in higgs mass, b-quark asymmetry data, the SLD left right asymmetry data, or additional new physics., Comment: 28 pages, 15 eps figures. Minor changes for clarification. Version to appear in Phys. Rev. D

The top condensate see-saw mechanism of Dobrescu and Hill allows electroweak symmetry to be broken while deferring the problem of flavour to an electroweak singlet, massive sector. We provide an extended version of the singlet sector that naturally accommodates realistic masses for all the standard model fermions, which play an equal role in breaking electroweak symmetry. The models result in a relatively light composite Higgs sector with masses typically in the range of (400-700)~GeV. In more complete models the dynamics will presumably be driven by a broken gauged family or flavour symmetry group. As an example of the higher scale dynamics a fully dynamical model of the quark sector with a GIM mechanism is presented, based on an earlier top condensation model of King using broken family gauge symmetry interactions (that model was itself based on a technicolour model of Georgi). The crucial extra ingredient is a reinterpretation of the condensates that form when several gauge groups become strong close to the same scale. A related technicolour model of Randall which naturally includes the leptons too may also be adapted to this scenario. We discuss the low energy constraints on the massive gauge bosons and scalars of these models as well as their phenomenology at the TeV scale., Comment: 22 pages, 3 figs

Quark matter at sufficiently high density exhibits color superconductivity, due to attractive gluonic interactions. At lower densities of order $\Lambda_{QCD}^3$, it has been proposed that instanton generated vertices may play an important role in the Cooper pair formation. We study the renormalization group flow to the Fermi surface of the full set of couplings generated by gluonic and instanton interactions. In earlier work we showed that if the gluonic interactions dominate at the matching scale, their running determines the scale of the Cooper pair formation Delta. Here we consider all possibilities, including the one in which the instanton interactions dominate all others at the matching scale. In the latter case we find that a number of additional induced couplings (including the gluonic ones) reach their Landau poles almost simultaneously with the instanton vertex. Presumably all contribute to the Cooper pair formation. The most important consequence of including all the couplings is a large increase in the gap size Delta., Comment: 10 pages, LaTeX, 4 eps files, extra discussion

We investigate the Fermi Liquid theory of high density QCD. Using the renormalization group (RG), we determine the behavior of effective fermion interactions near the Fermi surface. At sufficiently high densities the matching between the Fermi Liquid theory and QCD can be accomplished in perturbation theory and a reliable calculation of Cooper pair formation performed, modulo the existence of a magnetic screening mass for the gluon. The presence of a chemical potential leads to different RG flows for sub-components of the effective interactions which would ordinarily be linked by Lorentz invariance. We also study instanton-induced operators and find that near the Fermi surface they are likely to be subdominant relative to operators induced by perturbative gluon exchange. We discuss the implications of our results for the phase structure of QCD at finite baryon density and temperature., Comment: LaTEX, 16 pages, 2 eps figures, minor corrections

The field theories on the surface of non-supersymmetric D-brane constructions are identified. By moving to M-theory a semi-classical, strong coupling expansion to the IR non-supersymmetric gauge dynamics is obtained. The solution is consistent with the formation of a quark condensate but there is evidence that in moving to strong coupling scalar degrees of freedom have not decoupled., Comment: 9 pages, Latex + sprocl.sty (included), Talk presented at PASCOS98 and Continuous Advances in QCD 98

The curves that describe the M-theoretic extension of type IIA string configurations with non-supersymmetric field theories on their surface exhibit a duality map. The map suggests a continued link between a SU(N) gauge theory with F flavours and an SU(F-N) gauge theory with F flavours (the duality of supersymmetric QCD) even when the gaugino mass is taken to infinity. Within the context of the field theory such a duality only continues to make sense if the scalar fields remain light. We discuss the difficulties of decoupling the scalars within this framework., Comment: 14 pages, Latex, minor corrections

A set of non-supersymmetric minimal area embeddings of an M-theory 5-brane are considered. The field theories on the surface of the 5-brane have the field content of N=2 SQCD with fundamental representation matter fields. By suitable choice of curve parameters the N=2 and N=1 superpartners may be decoupled leaving a semi-classical approximation to QCD with massive quarks. As supersymmetry breaking is introduced a quark condensate grows breaking the low energy $Z_{F}$ flavour symmetry. At $\theta =$ (odd) $\pi$ spontaneous CP violation is observed consistent with that of the QCD chiral lagrangian., Comment: 16 pages, 1 ps figure, corrected some typos, updated references

We identify the 4D field theories living on the world volume of D4 branes in non-supersymmetric type IIA string theory constructions. They are softly broken N=2 SQCD with the breakings introduced through vevs of the auxilliary fields in the spurion coupling field. Exact solutions of these theories for perturbing soft breakings exist in the literature. We calculate the ratios of string tensions in softly broken N=2 SU(N) gauge theory testing the recently proposed M-theory prediction. The semi-classical result of M-theory is renormalized in the non-supersymmetric models., Comment: 15 pages, Latex, clarified discussion and updated references

Supersymmetric Yang Mills theory is directly accessible to lattice simulations using current methodology, and can provide a non-trivial check of recent exact results in SQCD. In order to tune the lattice simulation to the supersymmetric point it is neccessary to understand the behavior of the theory with a small supersymmetry breaking gaugino mass. We introduce a soft breaking gaugino mass in a controlled fashion using a spurion analysis. We compute the gluino condensate, vacuum energy and bound-state masses as a function of the gaugino mass, providing more readily accessible predictions which still test the supersymmetric results. Finally we discuss diagnostics for obtaining the bare lattice parameters that correspond to the supersymmetric continuum limit., Comment: 17 pages, Latex, some corrections, added discussion

We review progress in studying the solutions of SQCD in the presence of explicit, soft SUSY breaking terms. Massive N=1 SQCD in the presence of a small gaugino mass leads to a controlled solution which has interesting phase structure with changing theta angle reminiscent of the QCD chiral Lagrangian. Current attempts to test the solutions of pure glue SQCD on the lattice require a theoretical understanding of the theory with small gaugino mass in order to understand the approach to the SUSY point. We provide such a description making predictions for the gaugino condensate and lightest bound state masses. Finally we briefly review recent D-brane constructions of 4D gauge theories in string theory including a non-supersymmetric configuration. We identify this configuration with softly broken N=2 SQCD., Comment: 8 pages, Latex, espcrc2, 2 figs, talk presented at SUSY 97, reference added

Recently, a D-brane construction in type IIA string theory was shown to yield the electric/magnetic duality of four dimensional N=1 supersymmetric U(N_c) gauge theories with N_f flavours of quark. We present here an extension of that construction which yields the electric/magnetic duality for the SO(N_c) and USp(N_c) gauge theories with N_f quarks, by adding an orientifold plane which is consistent with the supersymmetry. Due to the intersection of the orientifold plane with the NS-NS fivebranes already present, new features arise which are crucial in determining the correct final structure of the dualities., Comment: 24 pages, harvmac.tex (b), 6 figures, epsf.tex (Major improvements to figures; minor improvements to text.)

We discuss the introduction of soft breaking terms into the exact solutions of N=1 SQCD using a spurion analysis. The spurion symmetries are not sufficient to determine the behavior of models in which squark or gaugino masses alone are introduced. However, a controlled approximation is obtained in some cases if a supersymmetric mass is first introduced for the matter fields. We present low-energy solutions for two models with perturbing soft breaking terms, one with a gaugino mass and one with squark mixing. These models have non-trivial theta angle dependence and exhibit phase transitions at non-zero theta angle analogous to those found in the chiral Lagrangian description of QCD., Comment: 10 pages, Latex, one eps figure

We introduce a diagramatic notation for supersymmetric gauge theories. The notation is a tool for exploring duality and helps to present the field content of more complicated models in a simple visual way. We introduce the notation with a few examples from the literature. The power of the formalism allows us to study new models with gauge group $(SU(N))^k$ and their duals. Amongst these are models which, contrary to a naive analysis, possess no conformal phase., Comment: 20 pages, LaTeX, figures included

Extended technicolor (ETC) theories typically require ETC gauge bosons lighter than of order 1 TeV, to perturbatively generate the $t$ quark mass. We point out that explicit models of $t-b$ mass splitting also typically contain additional TeV scale ETC gauge bosons transforming in the {\it adjoint} of technicolor, leading to large weak-isospin-breaking effects observable in the $\rho$ parameter. Viable ETC models may thus require a lowest ETC scale of order 10 TeV, with relatively strong and finely tuned couplings to generate $m_t$. Such models do not generate observable corrections to the $Zb{\bar b}$ vertex., Comment: LaTex, 12 pages, including 2 EPS figures in 5 files