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Full-Text Articles in Physics

Non-Isotropy Of The Cmb Power Spectrum In Single Field Inflation, John Donoghue, Koushik Dutta, Andreas Ross Jul 2009

Non-Isotropy Of The Cmb Power Spectrum In Single Field Inflation, John Donoghue, Koushik Dutta, Andreas Ross

John Donoghue

Contaldi et al. [1] have suggested that an initial period of kinetic energy domination in single field inflation may explain the lack of CMB power at large angular scales. We note that in this situation it is natural that there also be a spatial gradient in the initial value of the inflaton field, and that this can provide a spatial asymmetry in the observed CMB power spectrum, manifest at low multipoles. We investigate the nature of this asymmetry and comment on its relation to possible anomalies at low multipoles.


Gauge Federation As An Alternative To Unification, John Donoghue, Preema Pais May 2009

Gauge Federation As An Alternative To Unification, John Donoghue, Preema Pais

John Donoghue

We motivate and explore the possibility that extra SU(N) gauge groups may exist independently of the Standard Model groups, yet not be subgroups of some grand unified group. We study the running of the coupling constants as a potential evidence for a common origin of all the gauge theories. Several different example are displayed. Some of the multiple options involve physics at the TeV scale.


Comments On The Minimal Vectorial Standard Model, Mohamed M. Anber, Ufuk Aydemir, John Donoghue, Preema Pais Jan 2009

Comments On The Minimal Vectorial Standard Model, Mohamed M. Anber, Ufuk Aydemir, John Donoghue, Preema Pais

John Donoghue

We explore the available parameter space of the minimal vectorial Standard Model. In this theory, the gauge currents are initially vectorial but the Higgs sector produces chiral mass eigenstates, leading to a set of heavy right-handed mirror particles. We describe the phenomenology of the residual parameter space and suggest that the model will be readily tested at the LHC.


Constraints On The Variability Of Quark Masses From Nuclear Binding, Thibault Damour, John Donoghue Jul 2008

Constraints On The Variability Of Quark Masses From Nuclear Binding, Thibault Damour, John Donoghue

John Donoghue

Based on recent work on nuclear binding, we update and extend the anthropic constraints on the light quark masses, with results that are more tightly constrained than previously obtained. We find that heavy nuclei would fall apart (because the attractive nuclear central potential becomes too weak) if the sum of the light quark masses m_u+m_d would exceed their physical values by 64% (at 95% confidence level). We summarize the anthropic constraints that follow from requiring the existence both of heavy atoms and of hydrogen. With the additional assumption that the quark Yukawa couplings do not vary, these constraints provide ...


On The Parameterization Dependence Of The Energy Momentum Tensor And The Metric, N. E. J. Bjerrum-Bohr, John Donoghue, Barry R. Holstein May 2007

On The Parameterization Dependence Of The Energy Momentum Tensor And The Metric, N. E. J. Bjerrum-Bohr, John Donoghue, Barry R. Holstein

John Donoghue

We use results by Kirilin to show that in general relativity the nonleading terms in the energy-momentum tensor of a particle depends on the parameterization of the gravitational field. While the classical metric that is calculated from this source, used to define the leading long-distance corrections to the metric, also has a parameteriztion dependence, it can be removed by a coordinate change. Thus the classical observables are parameterization independent. The quantum effects that emerge within the same calculation of the metric also depend on the parameterization and a full quantum calculation requires the inclusion of further diagrams. However, within a ...


Sigma Exchange In The Nuclear Force And Effective Field Theory, John Donoghue Dec 2006

Sigma Exchange In The Nuclear Force And Effective Field Theory, John Donoghue

John Donoghue

In the phenomenological description of the nuclear interaction a crucial role is traditionally played by the exchange of a scalar I=0 meson, the sigma, of mass 500-600 MeV, which however is not seen clearly in the particle spectrum and which has a very ambiguous status in QCD. I show that a remarkably simple and reasonably controlled combination of ingredients can reproduce the features of this part of the nuclear force. The use of chiral perturbation theory calculations for two pion exchange supplemented by the Omnes function for pion rescattering suffices to reproduce the magnitude and shape of the exchange ...


The Nuclear Central Force In The Chiral Limit, John Donoghue Aug 2006

The Nuclear Central Force In The Chiral Limit, John Donoghue

John Donoghue

Chiral perturbation theory supplemented by the Omnes function is employed to study the strength of the isoscalar central nuclear interaction, G_S, in the chiral limit vs the physical case. A very large modification is seen, i.e. eta_s = G_S ~ chiral /G_S ~ physical = 1.37 +- 0.10 . This large effect is seen to arise dominantly at low energy from the extra contributions made by massless pions at energies near the physical threshold where the physical spectral function must vanish kinematically. The slope away from the chiral limit, d_S, is also calculated and is correspondingly large. I also explain why this large ...


Quark And Lepton Masses And Mixing In The Landscape, John Donoghue, Koushik Dutta, Andreas Ross Jun 2006

Quark And Lepton Masses And Mixing In The Landscape, John Donoghue, Koushik Dutta, Andreas Ross

John Donoghue

Even if quark and lepton masses are not uniquely predicted by the fundamental theory, as may be the case in the string theory landscape, nevertheless their pattern may reveal features of the underlying theory. We use statistical techniques to show that the observed masses appear to be representative of a scale invariant distribution, rho(m) ~ 1/m. If we extend this distribution to include all the Yukawa couplings, we show that the resulting CKM matrix elements typically show a hierarchical pattern similar to observations. The Jarlskog invariant measuring the amount of CP violation is also well reproduced in magnitude. We ...


Long Distance Effects And Strangeness In The Nucleon, John Donoghue, Barry R. Holstein, Tobias Huber, Andreas Ross Dec 2005

Long Distance Effects And Strangeness In The Nucleon, John Donoghue, Barry R. Holstein, Tobias Huber, Andreas Ross

John Donoghue

We discuss the calculation of the strange magnetic radius of the proton in chiral perturbation theory. In particular we investigate the low energy component of the loop integrals involving kaons. We separate the chiral calculation into a low energy part and a high energy component through use of a momentum space separation scale. This separation shows that most of the chiral calculation comes from high energies where the effective field theory treatment is not valid. The resulting low energy prediction is in better agreement with dispersive treatments. Finally, we briefly discuss magnetic moments and show how our techniques can help ...


Isotropy Of The Early Universe From Cmb Anisotropies, Evan P. Donoghue, John Donoghue Feb 2005

Isotropy Of The Early Universe From Cmb Anisotropies, Evan P. Donoghue, John Donoghue

John Donoghue

The acoustic peak in the CMB power spectrum is sensitive to causal processes and cosmological parameters in the early universe up to the time of last scattering. We provide limits on correlated spatial variations of the peak height and peak position and interpret these as constraints on the spatial variation of the cosmological parameters (baryon density, cold dark matter density and cosmological constant as well as the amplitude and tilt of the original fluctuations). We utilize recent work of Hansen, Banday and Gorski (HBG) who have studied the spatial isotropy of the power spectrum as measured by WMAP by performing ...


Classical Physics And Quantum Loops, Barry R. Holstein, John Donoghue Nov 2004

Classical Physics And Quantum Loops, Barry R. Holstein, John Donoghue

John Donoghue

The standard picture of the loop expansion associates a factor of h-bar with each loop, suggesting that the tree diagrams are to be associated with classical physics, while loop effects are quantum mechanical in nature. We discuss examples wherein classical effects arise from loop contributions and display the relationship between the classical terms and the long range effects of massless particles.


Dynamics Of M-Theory Vacua, John Donoghue May 2004

Dynamics Of M-Theory Vacua, John Donoghue

John Donoghue

At very early times, the universe was not in a vacuum state. Under the assumtion that the deviation from equillibrium was large, in particular that it is higher than the scale of inflation, we analyse the conditions for local transitions between states that are related to different vacua. All pathways lead to an attractor solution of a description of the universe by eternal inflation with domains that have different low energy parameters. The generic case favors transitions between states that have significantly different parameters rather than jumps between nearby states in parameter space. I argue that the strong CP problem ...


Long Distance Chiral Corrections In B Meson Amplitudes, Juan J. Sanz-Cillero, John Donoghue, Andreas Ross Jan 2004

Long Distance Chiral Corrections In B Meson Amplitudes, Juan J. Sanz-Cillero, John Donoghue, Andreas Ross

John Donoghue

We discuss the chiral corrections to f_B and B_B with particular emphasis on determining the portion of the correction that arises from long distance physics. For very small pion and kaon masses all of the usual corrections are truly long distance, while for larger masses the long distance portion decreases. These chiral corrections have been used to extrapolate lattice calculations towards the physical region of lighter masses. We show in particular that the chiral extrapolation is better behaved if only the long distance portion of the correction is used.


Quantum Corrections To The Schwarzschild And Kerr Metrics, N. E. J. Bjerrum-Bohr, John Donoghue, Barry R. Holstein Oct 2003

Quantum Corrections To The Schwarzschild And Kerr Metrics, N. E. J. Bjerrum-Bohr, John Donoghue, Barry R. Holstein

John Donoghue

We examine the corrections to the lowest order gravitational interactions of massive particles arising from gravitational radiative corrections. We show how the masslessness of the graviton and the gravitational selfinteractions imply the presence of nonanalytic pieces ;A2q2,;q2ln2q2, etc., in the form factors of the energy-momentum tensor and that these correspond to long range modifications of the metric tensor gmn of the form G2m2/r2,G2m\/r3, etc. The former coincide with well known solutions from classical general relativity, while the latter represent new quantum mechanical effects, whose strength and form is necessitated by the low energy quantum nature of ...


Quantum Gravitational Corrections To The Nonrelativistic Scattering Potential Of Two Masses, N. E. J. Bjerrum-Bohr, John Donoghue, Barry R. Holstein Apr 2003

Quantum Gravitational Corrections To The Nonrelativistic Scattering Potential Of Two Masses, N. E. J. Bjerrum-Bohr, John Donoghue, Barry R. Holstein

John Donoghue

We treat general relativity as an effective field theory, obtaining the full nonanalytic component of the scattering matrix potential to one-loop order. The lowest order vertex rules for the resulting effective field theory are presented and the one-loop diagrams which yield the leading nonrelativistic post-Newtonian and quantum corrections to the gravitational scattering amplitude to second order in G are calculated in detail. The Fourier transformed amplitudes yield a nonrelativistic potential and our result is discussed in relation to previous calculations. The definition of a potential is discussed as well and we show how the ambiguity of the potential under coordinate ...


Spatial Gradients In The Cosmological Constant, John Donoghue Jan 2003

Spatial Gradients In The Cosmological Constant, John Donoghue

John Donoghue

It is possible that there may be differences in the fundamental physical parameters from one side of the observed universe to the other. I show that the cosmological constant is likely to be the most sensitive of the physical parameters to possible spatial variation, because a small variation in any of the other parameters produces a huge variation of the cosmological constant. It therefore provides a very powerful {\em indirect} evidence against spatial gradients or temporal variation in the other fundamental physical parameters, at least 40 orders of magnitude more powerful than direct experimental constraints. Moreover, a gradient may potentially ...


Improved Determination Of The Electroweak Penguin Contribution To E’/E In The Chiral Limit, Vincenzo Cirigliano, John Donoghue, Eugene Golowich, Kim Maltman Jan 2003

Improved Determination Of The Electroweak Penguin Contribution To E’/E In The Chiral Limit, Vincenzo Cirigliano, John Donoghue, Eugene Golowich, Kim Maltman

John Donoghue

We perform a finite energy sum rule analysis of the flavor ud two-point V-A current correlator, Delta Pi (Q^2). The analysis, which is performed using both the ALEPH and OPAL databases for the V-A spectral function, Delta rho, allows us to extract the dimension six V-A OPE coefficient, a_6, which is related to the matrix element of the electroweak penguin operator, Q_8, by chiral symmetry. The result for a_6 leads directly to the improved (chiral limit) determination epsilon'/epsilon = (- 15.0 +- 2.7) 10^{-4}. Determination of higher dimension OPE contributions also allows us to perform an independent test ...


Quantum Corrections To The Reissner–Nordström And Kerr-Newman Metrics, John Donoghue, Barry R. Holstein, Björn Garbrecht, Thomas Konstandin Jan 2002

Quantum Corrections To The Reissner–Nordström And Kerr-Newman Metrics, John Donoghue, Barry R. Holstein, Björn Garbrecht, Thomas Konstandin

John Donoghue

We use effective field theory techniques to examine the quantum corrections to the gravitational metrics of charged particles, with and without spin. In momentum space the masslessness of the photon implies the presence of non-analytic pieces , q2log(−q2), etc. in the form factors of the energy–momentum tensor. We show how the former reproduces the classical non-linear terms of the Reissner–Nordström and Kerr–Newman metrics while the latter can be interpreted as quantum corrections to these metrics, of order ℏ/mr3


Random Values Of The Cosmological Constant, John Donoghue Jan 2000

Random Values Of The Cosmological Constant, John Donoghue

John Donoghue

One way that an anthropic selection mechanism may be manifest in a physical theory involves multiple domains in the universe with different values of the physical parameters. If this mechanism is to be relevant for understanding the small observed value of the cosmological constant, it may involve a mechanism by which some contributions to the cosmological constant can be fixed at a continuous range of values in the different domains. I study the properties of four possible mechanisms, including the possibility of the Hubble damping of a scalar field with an extremely flat potential. Another interesting possibility involves fixed random ...


Dimension Eight Operators In The Weak Operator Product Expansion, Vincenzo Cirigliano, John Donoghue, Eugene Golowich Jan 2000

Dimension Eight Operators In The Weak Operator Product Expansion, Vincenzo Cirigliano, John Donoghue, Eugene Golowich

John Donoghue

We expose a potential flaw in standard treatments of weak decay amplitudes, including that of epsilon'/epsilon. We show that (contrary to conventional wisdom) dimension-eight operators do contribute to weak amplitudes, at order G_F alpha_s and without 1/M_W^2 suppression. We demonstrate the existence of these operators with a simple weak hamiltonian and proceed to discuss their contribution in a general context. We estimate the effect of dimension-eight operators to be at the 100% level in a sum rule determination of the operator O_7 for mu = 1.5 GeV, suggesting presently available values of mu are too low to ...