arXiv subjects

Peter Suranyi

Publications and source records attributed to Peter Suranyi.

29 records · Page 2Linked to original sources

arXiv2014

On the Stability of D7 - anti-D7 Probes in Near-conformal Backgrounds

We investigate the perturbative stability of a nonsupersymmetric D7 - anti-D7 brane embedding in a particular class of type IIB backgrounds. These backgrounds are the gravitational duals of certain strongly-coupled gauge theories, that exhibit a nearly conformal regime (known as a walking regime). Previous studies in the literature have led to conflicting results as to whether the spectrum of fluctuations around the flavor D7 - anti-D7 embedding has a tachyonic mode or not. Here we reconsider the problem with a new analytical method and recover the previously obtained numerical results. We also point out that the earlier treatments relied on a coordinate system, in which it was not possible to take into account fluctuations of the point of confluence of the D7 - anti-D7 branes. Using an improved coordinate system, we confirm the presence of a normalizable tachyonic mode in this model, in agreement with the numerical calculations. Finally, we comment on the possibility of turning on worldvolume flux to stabilize the probe branes configuration.

hep-th↗

arXiv2014

Stability of D-brane embeddings in nontrivial backgrounds

We propose a new analytical method for determining whether nonsupersymmetric probe branes embedded in nontrivial backgrounds are perturbatively stable or not. The method is based on a relationship between zero mass solutions of the relevant DBI equations of motion and tachyonic solutions. Furthermore, due to the above relation, the question, of whether a classical solution is stable or not, can be answered simply by studying the derivatives of that solution with respect to its integration constants. Finally, we illustrate the efficiency of this method by applying it to several interesting examples.

hep-th↗

arXiv2013

Glueball Spectrum in a Gauge Theory with Two Dynamical Scales

We investigate the glueball spectrum of a strongly coupled gauge theory with two dynamical scales. The main tool is the use of the gauge/gravity duality. The model we study has a known graviational dual, which arises from a type IIB D-brane configuration. It exhibits two dynamical scales, separated by a nearly conformal region. Thus, it is of great interest for the study of walking in gauge theories. By using the gravitational description, we are able to compute analytically the glueball mass spectrum in a certain range of the parameter space of the theory. Within that range, we do not find a light state that could be associated with a slight breaking of conformal invariance. Finally, we show that in this model there can be an order of magnitude hierarchy between the scale of confinement, given by the lowest glueball mass, and the scale of chiral symmetry breaking, determined by the lowest vector-meson mass.

hep-th↗

arXiv2012

Scalar Mesons in Holographic Walking Technicolor

We study the spectrum of scalar mesons in the holographic dual of walking technicolor, obtained by embedding D7 - anti-D7 probe branes in a certain type IIB background. The scalar mesons arise from fluctuations of the probe techniflavour branes and complement the (axial-)vector meson spectra that we investigated in earlier work. By explicitly finding the spectrum of scalar masses, we show that the nonsupersymmetric D7 - anti-D7 embedding is stable with respect to such fluctuations. Interestingly, it turns out that the mass splitting between the scalar and vector meson spectra is of subleading order in a small parameter expansion. It is noteworthy that this near-degeneracy may not be entirely due to a small amount of supersymmetry breaking and thus could indicate the presence of some other (approximate) symmetry in the problem.

hep-th↗

arXiv2011

Holographic Walking Technicolor from D-branes

We investigate a model of dynamical electroweak symmetry breaking via a dual gravitational description. The gravity dual is obtained by embedding a D7 - anti-D7 pair of branes into a type IIB background that is dual to a walking gauge theory. We develop further a previous study of this model. In particular, we show that there is a nontrivial relation that needs to be satisfied in order for axial-vector modes to exist. Furthermore, we compute explicitly the electroweak S parameter. The result is positive-definite and, as was to be expected, much smaller than in earlier QCD-like D-brane constructions. We also find the masses and decay constants of the vector and axial-vector mesons in this model. This allows us to obtain another estimate for S by summing the contributions of the discrete states. It is noteworthy that, in contrast to previous holographic studies, the sum of the first several lowest-lying states does give a very good approximation to the full answer.

hep-th↗

arXiv2008

A 6 dimensional $(Z_{2})^3$ symmetric model with warped physical space

The Randall-Sundrum model is studied in 6 dimension with AdS$_4$ or dS$_4$ metric in the physical 4 dimensional space. Two solutions are found, one with induced 5-dimensional gravity terms added to the induced cosmological constant terms. We study the graviton modes in both solutions by transforming the mass eigenvalue equation to a Schrodinger equation with a volcano potential. The spectrum of gravitational excitations depends on the input parameters of the theory, the six dimensional and the effective four-dimensional cosmological constants. The model gives a physically acceptable spectrum if the 4 dimensional cosmological constant is sufficiently small.

hep-th↗

arXiv2000

Vortes solutions in nonabelian Higgs theories

A new class of vortex solutions is found in SU(2) gauge theories with two adjoint representation Higgs bosons. Implications of these new solutions and their possible connection with Center Gauge fixed pure gauge theories are discussed.

hep-lat↗

arXiv1999

Lattice field theories with an energy current

We investigate a lattice scalar field theory in the presence of a bias favouring the establishment of an energy current, as a model for stationary nonequilibrium processes at low temperature in a non-integrable system. There is a transition at a finite value of the bias to a gapless modulated phase which carries a classical current; however, unlike in similar, integrable, models, quantum effects also allow for a non-zero current at arbitrarily small bias. The transition is second order in the magnetically disordered phase, but is pre-empted by a first-order transition in the ferromagnetic case, at least at the mean-field level.

cond-mat.stat-mech↗

arXiv1998

Improved Mass Constraints in the MSSM from Vacuum Stability

Using a simple numerical method, we compute the stability of the MSSM vacuum with respect to tunneling. The stability criterion is then used to put restrictions on the mass parameters. These restrictions are necessary conditions for the vacuum stability and compliment the existing sufficiency conditions obtained analytically.

hep-ph↗

arXiv1992

Hamiltonian Effective Potential

A Hamiltonian effective potential (the logarithm of the square of the wave functional) is defined and calculated at the tree and one loop levels in a $ϕ^4$ scalar field theory. The loop expansion for eigenfunctionals is equivalent to the combination of WKB expansion and an expansion around constant field configurations. The results are compared with those obtained from the Lagrangian effective potential. While at tree level the results from the two methods coincide, at one loop level they differ. Our result at one loop level is that the reflection symmetry is not broken at $m^2\geq0$.

hep-ph↗

arXiv1992

A New Field Theoretic Approach to Criticality

A reorganized perturbation expansion with a propagator of soft infrared behavior is used to study the critical behavior of the mass gap. The condition of relativistic covariance fixes the form of the soft propagator. Finite approximants to the correlation critical exponent can be obtained in every order of the modified, soft perturbation expansion. Alternatively, a convergent series of exponents in large orders of the soft perturbation expansion is provided by the renormalization group in all spatial dimensions, $1\leq D\leq3$. The result of the $ε$-expansion is recovered in the $D\rightarrow 3 $ limit.

hep-th↗