arXiv subjects

Matti Jarvinen

Publications and source records attributed to Matti Jarvinen.

60 records · Page 4Linked to original sources

arXiv2008

The Electroweak Phase Transition in Nearly Conformal Technicolor

We examine the temperature-dependent electroweak phase transition in extensions of the Standard Model in which the electroweak symmetry is spontaneously broken via strongly coupled, nearly-conformal dynamics. In particular, we focus on the low energy effective theory used to describe Minimal Walking Technicolor at the phase transition. Using the one-loop effective potential with ring improvement, we identify significant regions of parameter space which yield a sufficiently strong first order transition for electroweak baryogenesis. The composite particle spectrum corresponding to these regions can be produced and studied at the Large Hadron Collider experiment. We note the possible emergence of a second phase transition at lower temperatures. This occurs when the underlying technicolor theory possesses a nontrivial center symmetry.

hep-ph↗

arXiv2008

The Partition Function of a Multi-Component Coulomb Gas on a Circle

We study a two-dimensional Coulomb gas consisting of a mixture of particles carrying various positive multiple integer charges, confined on a unit circle. We consider the system in the canonical and grand canonical ensembles, and attempt to calculate the partition functions analytically, using Toeplitz and confluent Vandermonde determinants. Just like in the simple one-component system (Dyson gas), the partition functions simplify at special temperature $β=2$, allowing us to find compact expressions for them.

cond-mat.stat-mech↗

arXiv2007

Disk Partition Function and Oscillatory Rolling Tachyons

An exact cubic open string field theory rolling tachyon solution was recently found by Kiermaier et. al. and Schnabl. This oscillatory solution has been argued to be related by a field redefinition to the simple exponential rolling tachyon deformation of boundary conformal theory. In the latter approach, the disk partition function takes a simple form. Out of curiosity, we compute the disk partition function for an oscillatory tachyon profile, and find that the result is nevertheless almost the same.

hep-th↗

arXiv2007

Perturbative gauge theory in a background

Motivated by the gluon condensate in QCD we study the perturbative expansion of a gauge theory in the presence of gauge bosons of vanishing momentum, in the specific case of an abelian theory. The background is characterised by a dimensionful parameter $Λ$ affecting only the on-shell prescription of the free (abelian) gluon propagator. When summed to all orders in $gΛ$ the modification is equivalent to evaluating standard Green functions in a pure gauge field with an imaginary gauge parameter $\propto Λ$. We show how to calculate the corresponding dressed Green functions, which are Poincare and gauge covariant. We evaluate the expressions for the dressed quark and $q \bar q$ propagators, imposing as boundary condition that they approach the standard perturbative form in the short-distance limit ($|p^2|\to\infty$). The on-shell ($p^2=m^2$) pole of the free quark propagator is removed for any $Λ> 0$, and replaced by a discontinuity which vanishes exponentially with $p^2$. The dressing introduces an effective interaction between quarks and antiquarks which is enhanced at low relative 3-momentum. Further study should allow to identify the (bound) eigenstates of propagation and determine whether they define a unitary S-matrix. When the quark mass is zero there is a euclidean propagator solution which breaks chiral symmetry spontaneously. We study some aspects of the massless pion contribution to axial vector correlators and derive the $πq \bar q$ form factor.

hep-ph↗

arXiv2007

Single Spin Asymmetry at Large x_F and k_T

The large single spin asymmetries observed at high momentum fractions x_F and transverse momenta k_T in p^\uparrow p -> π(x_F,k_T)+X as well as in pp -> Λ^\uparrow(x_F,k_T)+X suggest that soft helicity flip processes are coherent with hard scattering. Such coherence can be maintained if x_F -> 1 as k_T -> \infty, while k_T^2(1-x_F) \sim Λ_QCD^2 stays fixed. The entire hadron wave function, rather than a single quark, then contributes to the scattering process. Analogous coherence effects have been seen experimentally in the Drell-Yan process at high x_F. We find that the p^\uparrow p -> π(x_F,k_T)+X production amplitudes have large dynamic phases and that helicity flip contributions are unsuppressed in this limit, giving rise to potentially large single spin asymmetries.

hep-ph↗

arXiv2005

Soft Rescattering in DIS: Effects of Helicity Flip

Soft rescattering in hard QCD processes may involve non-perturbative, chiral symmetry breaking interactions. We find that rescattering which changes the helicity of the struck quark gives rise to a leading twist single spin asymmetry in semi-inclusive DIS, the angular dependence of which is the same as that usually ascribed to the Collins effect. We argue that helicity-changing rescattering can contribute also to $k_\perp$-integrated parton distributions.

hep-ph↗