arXiv subjects

Witold Skiba

Publications and source records attributed to Witold Skiba.

At least 55 records · Page 3Linked to original sources

arXiv2005

Little Higgs Models and Electroweak Measurements

Using effective field theory approach, we study the constraints from electroweak data on the SU(5)/SO(5), SU(6)/SP(6), SU(3)xU(1) little Higgs models and their variations. We construct an effective theory valid above the electroweak symmetry breaking scale in these models that includes dimension-six operators induced by integrating out heavy fields. We calculate the constraints on the models using the results of hep-ph/0412166, where bounds on arbitrary linear combinations of flavor and CP conserving dimension-six operators are given. We present the constraints in terms of the bounds on the masses of heavy fermions and heavy gauge bosons. The constraints are often stringent, but in some regions of the parameter space the constraints are mild enough and do not imply significant fine-tuning.

hep-ph↗

arXiv2004

Little Higgses and Turtles

We present an ultra-violet extension of the "simplest little Higgs" model. The model marries the simplest little Higgs at low energies to two copies of the "littlest Higgs'' at higher energies. The result is a weakly coupled theory below 100 TeV with a naturally light Higgs. The higher cutoff suppresses the contributions of strongly coupled dynamics to dangerous operators such as those which induce flavor changing neutral currents and CP violation. We briefly survey the distinctive phenomenology of the model.

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arXiv2004

Family Unification on an Orbifold

We construct a family-unified model on a Z_2xZ_2 orbifold in five dimensions. The model is based on a supersymmetric SU(7) gauge theory. The gauge group is broken by orbifold boundary conditions to a product of grand unified SU(5) and SU(2)xU(1) flavor symmetry. The structure of Yukawa matrices is generated by an interplay between spontaneous breaking of flavor symmetry and geometric factors arising due to field localization in the extra dimension.

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arXiv2003

A Simple Model of two Little Higgses

We construct a little Higgs model using a simple global symmetry group SU(9) spontaneously broken to SU(8). The electroweak interactions are extended to SU(3)xU(1) and embedded in SU(9). At the electroweak scale, our model is a two Higgs-doublet model. At the TeV scale, there are additional states, which are responsible for the cancellation of one loop quadratic divergences. We compute the effects of heavy states on the precision electroweak observables and find that the lower bounds on the masses of heavy gauge bosons and fermions are between 1 and 2 TeV.

hep-ph↗

arXiv2002

N=1 Supersymmetric Product Group Theories in the Coulomb Phase

We study the low-energy behavior of N=1 supersymmetric gauge theories with product gauge groups SU(N)^M and M chiral superfields transforming in the fundamental representation of two of the SU(N) factors. These theories are in the Coulomb phase with an unbroken U(1)^(N-1) gauge group. For N >= 3, M >= 3 the theories are chiral. The low-energy gauge kinetic functions can be obtained from hyperelliptic curves which we derive by considering various limits of the theories. We present several consistency checks of the curves including confinement through the addition of mass perturbations and other limits.

hep-th↗

arXiv2002

Little Higgses from an Antisymmetric Condensate

We construct an SU(6)/Sp(6) non-linear sigma model in which the Higgses arise as pseudo-Goldstone bosons. There are two Higgs doublets whose masses have no one-loop quadratic sensitivity to the cutoff of the effective theory, which can be at around 10 TeV. The Higgs potential is generated by gauge and Yukawa interactions, and is distinctly different from that of the minimal supersymmetric standard model. At the TeV scale, the new bosonic degrees of freedom are a single neutral complex scalar and a second copy of SU(2)xU(1) gauge bosons. Additional vector-like pairs of colored fermions are also present.

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arXiv2002

PP-wave string interactions from perturbative Yang-Mills theory

Recently, Berenstein et al. have proposed a duality between a sector of N=4 super-Yang-Mills theory with large R-charge J, and string theory in a pp-wave background. In the limit considered, the effective 't Hooft coupling has been argued to be lambda'=g_{YM}^2 N/J^2=1/(mu p^+ alpha')^2. We study Yang-Mills theory at small lambda' (large mu) with a view to reproducing string interactions. We demonstrate that the effective genus counting parameter of the Yang-Mills theory is g_2^2=J^4/N^2=(4 pi g_s)^2 (mu p^+ alpha')^4, the effective two-dimensional Newton constant for strings propagating on the pp-wave background. We identify g_2 sqrt{lambda'} as the effective coupling between a wide class of excited string states on the pp-wave background. We compute the anomalous dimensions of BMN operators at first order in g_2^2 and lambda' and interpret our result as the genus one mass renormalization of the corresponding string state. We postulate a relation between the three-string vertex function and the gauge theory three-point function and compare our proposal to string field theory. We utilize this proposal, together with quantum mechanical perturbation theory, to recompute the genus one energy shift of string states, and find precise agreement with our earlier computation.

hep-th↗

arXiv2002

Localized Fermions and Anomaly Inflow via Deconstruction

We study fermion localization in gauge theory space. We consider four dimensional product gauge groups in which light chiral fermions transform under different gauge factors of the product group. This construction provides a suppression of higher dimensional operators. For example, it can be used to suppress dangerous proton decay operators. The anomalies associated with the light chiral fermions are compensated by Wess-Zumino terms, which in the continuum limit reproduce the five dimensional Chern-Simons term.

hep-ph↗

arXiv2001

Mother Moose: Generating Extra Dimensions from Simple Groups at Large N

We show that there exists a correspondence between four dimensional gauge theories with simple groups and higher dimensional gauge theories at large N. As an example, we show that a four dimensional {N}=2 supersymmetric SU(N) gauge theory, on the Higgs branch, has the same correlators as a five dimensional SU(N) gauge theory in the limit of large N provided the couplings are appropriately rescaled. We show that our results can be applied to the AdS/CFT correspondence to derive correlators of five or more dimensional gauge theories from solutions of five dimensional supergravity in the large t'Hooft coupling limit.

hep-th↗

arXiv2001

Radion Stabilization by Brane Matter

We find a static solution to Einstein's field equations on a five-dimensional orbifold with a compact S_1/Z_2 fifth direction and Poincare invariant 3+1 sections. The solution describes a theory with bulk cosmological constant and 3-branes at the orbifold fixed points which carry matter density and pressure in addition to tension. The radius of the fifth dimension is determined by the matter content of the branes. The ratio of the space and time components of the metric depends on the fifth coordinate. Thus, the speed of propagation of massless fields is path dependent. For example, bulk and brane fields propagate with different speeds.

hep-th↗

arXiv2000

On a Covariant Determination of Mass Scales in Warped Backgrounds

We propose a method of determining masses in brane scenarios which is independent of coordinate transformations. We apply our method to the scenario of Randall and Sundrum (RS) with two branes, which provides a solution to the hierarchy problem. The core of our proposal is the use of covariant equations and expressing all coordinate quantities in terms of invariant distances. In the RS model we find that massive brane fields propagate proper distances inversely proportional to masses that are not exponentially suppressed. The hierarchy between the gravitational and weak interactions is nevertheless preserved on the visible brane due to suppression of gravitational interactions on that brane. The towers of Kaluza-Klein states for bulk fields are observed to have different spacings on different branes when all masses are measured in units of the fundamental scale. Ratios of masses on each brane are the same in our covariant and the standard interpretations. Since masses of brane fields are not exponentiated, the fundamental scale of higher-dimensional gravity must be of the order of the weak scale.

hep-th↗

arXiv2000

Adding Matter to Poincare Invariant Branes

A solution to the cosmological constant problem has been proposed in which our universe is a 3-brane in a 5-dimensional spacetime. With a bulk scalar, the field equations admit a Poincare invariant brane solution regardless of the value of the cosmological constant (tension) on the brane. However, the solution does not include matter in the brane. We find new exact static solutions with matter density and pressure in the brane. We study small perturbations about these solutions. None seem consistent with observational cosmology. As a byproduct we find a class of new matterless static solutions and a non-static solution which, curiously, requires the string value for the dilaton coupling.

hep-th↗

arXiv2000

Minimal Gaugino Mediation

We propose Minimal Gaugino Mediation as the simplest known solution to the supersymmetric flavor and CP problems. The framework predicts a very minimal structure for the soft parameters at ultra-high energies: gaugino masses are unified and non-vanishing whereas all other soft supersymmetry breaking parameters vanish. We show that this boundary condition naturally arises from a small extra dimension and present a complete model which includes a new extra-dimensional solution to the mu problem. We briefly discuss the predicted superpartner spectrum as a function of the two parameters of the model. The commonly ignored renormalization group evolution above the GUT scale is crucial to the viability of Minimal Gaugino Mediation but does not introduce new model dependence.

hep-ph↗

arXiv2000

The Superpartner Spectrum of Gaugino Mediation

We compute the superpartner masses in a class of models with gaugino mediation (or no-scale) boundary conditions at a scale between the GUT and Planck scales. These models are compelling because they are simple, solve the supersymmetric flavor and CP problems, satisfy all constraints from colliders and cosmology, and predict the superpartner masses in terms of very few parameters. Our analysis includes the renormalization group evolution of the soft-breaking terms above the GUT scale. We show that the running above the GUT scale is largely model independent and find that a phenomenologically viable spectrum is obtained.

hep-ph↗

arXiv1999

Correlators of Short Multi-Trace Operators in N=4 Supersymmetric Yang-Mills

Multi-trace scalar operators in the (0,k,0) representations of SU(4)_R share many properties with their single-trace analogs. These multi-trace operators are primary fields of short representations of the N=4 superconformal group. Thus, they have protected dimensions. We show that two- and three-point correlator functions of such operators do not receive radiative corrections at order g^2 in perturbation theory for an arbitrary gauge group.

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arXiv1999

Beta Functions of Orbifold Theories and the Hierarchy Problem

We examine a class of gauge theories obtained by projecting out certain fields from an N=4 supersymmetric SU(N) gauge theory. These theories are non-supersymmetric and in the large N limit are known to be conformal. Recently it was proposed that the hierarchy problem could be solved by embedding the standard model in a theory of this kind with finite N. In order to check this claim one must find the conformal points of the theory. To do this we calculate the one-loop beta functions for the Yukawa and quartic scalar couplings. We find that with the beta functions set to zero the one-loop quadratic divergences are not canceled at sub-leading order in N; thus the hierarchy between the weak scale and the Planck scale is not stabilized unless N is of the order 10^28 or larger. We also find that at sub-leading orders in N renormalization induces new interactions, which were not present in the original Lagrangian.

hep-th↗

arXiv1999

Bonus Symmetry and the Operator Product Expansion of N=4 Super-Yang-Mills

The superconformal group of N=4 super-Yang-Mills has two types of operator representations: short and long. We conjecture that operator product expansions for which at least two of the three operators are short exactly respect a bonus U(1)_Y R-symmetry, which acts as an automorphism of the superconformal group. This conjecture is for arbitrary gauge group G and gauge coupling g_{YM}. A consequence is that n\leq 4-point functions involving only short operators exactly respect the U(1)_Y symmetry, as has been previously conjectured based on AdS duality. This, in turn, would imply that all n\leq 3 -point functions involving only short operators are not renormalized, as has also been previously conjectured and subjected to perturbative checks. It is argued that instantons are compatible with our conjecture. Some perturbative checks of the conjecture are presented and SL(2,Z) modular transformation properties are discussed.

hep-th↗

arXiv1998

Supersymmetric gauge theories with a free algebra of invariants

We study the low-energy dynamics of all N=1 supersymmetric gauge theories whose basic gauge invariant fields are unconstrained. This set includes all theories whose matter Dynkin index is less than the index of the adjoint representation. We study the dynamically generated superpotential in these theories, and show that there is a W=0 branch if and only if anomaly matching is satisfied at the origin. An interesting example studied in detail is SO(13) with a spinor, a theory with a dynamically generated W and no anomaly matching at the origin. It flows via the Higgs mechanism to SU(6) with a three-index antisymmetric tensor, a theory with a W=0 branch and anomaly matching at the origin.

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