REVIEW
Extending the Velocity-dependent One-scale String Evolution Model
High Energy Physics - Phenomenology · Submitted 30 Mar 2000 · 27 references
Pith's verdict: A solid methods paper that does what it claims analytically, but its headline accuracy claim and one figure caption need fixing before it's citable.
T0 · AI review
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Referee report
The paper
The paper claims
Cosmic string networks may need only one adjustable parameter, not two, once a new momentum formula and radiation backreaction are included.
The reading
What carries the argument
The carrying object is the two-equation VOS model: $2�,dL/dt=2HL(1+v_�infty^2)+L v_�infty^2/�ell_f+�tilde c v_�infty$ in the flat case, and $dv_�infty/dt=(1-v_�infty^2)[k/L-(2H+1/�ell_f)v_�infty]$, with $k$ no longer a free function but the ansatz $k(v)=�frac{2�sqrt2}{�pi}(1-v^2)(1+2�sqrt2 v^3)�frac{1-8v^6}{1+8v^6}$. The ansatz is built to reproduce the relativistic limit $k_{�rm rel}=�frac{2�sqrt2}{�pi}�frac{1-8v^6}{1+8v^6}$ and the non-relativistic limit $k_{�rm nr}=�frac{2�sqrt2}{�pi}(1-v^2)$. Backreaction adds $8�Sigma v_�infty^6$ to the right-hand side of the $L$ equation, with $�Sigma=�tilde�Gamma G�mu$ for local strings and $�Sigma=�tilde�Gamma/[2�pi�ln(t/�delta)]$ for global strings; this shifts the scaling solution by $�Delta=8�beta v_0^5�Sigma$ and, for large $�Sigma$, gives $�gamma�propto�Sigma^{1/7}$ and $v�propto�Sigma^{-1/7}$.
Extended reading notes
Core claim
The central claim is that the VOS model, with $k$ fixed by Eq. (3.9) and with a radiation-backreaction term added to the $L$ equation, describes the large-scale features of cosmic-string networks using only the loop-chopping efficiency $�tilde c=0.23�pm0.04$. The paper derives the two endpoints of $k(v)$—$k(1/�sqrt2)=0$ and $k_{�rm nr}=2�sqrt2/�pi$—and supplies an interpolating formula; it then shows that scale-invariant attractors still exist with backreaction, though their scaling values shift, and it gives the scaling solutions for power-law FRW backgrounds and for curvature-dominated open universes. The authors also report that the low densities seen in global-string simulations can be accommodated by a backreaction parameter $�Sigma_{�rm ax-sim}�approx3$, while cautioning that cosmological global strings have much larger $�ln(t/�delta)$ and therefore much smaller backreaction.
Load-bearing premise
The load-bearing premise is that the interpolating formula for the momentum parameter in Eq. (3.9), which joins the two derived limits, is correct at intermediate velocities; the paper fixes that bridge by fitting and defers the decisive high-resolution simulation check to a companion paper.
Editorial extensions
If this is right
- A realistic GUT-scale string network is not scale-invariant from just before matter-radiation equality to the present, so predictions that assume pure scaling during that interval can be biased.
- Electroweak-scale strings can remain friction-dominated until about three orders of magnitude after equality; for $�Omega_m=0.2,�Omega_�Lambda=0.8$ they are always non-relativistic today, which matters for superconducting-string and vorton studies.
- A cosmological-constant-dominated future makes the network freeze out and be conformally stretched, with $L�propto a$ and $v_�infty�propto a^{-1}$, lowering density and velocity and affecting large-angle CMB anisotropies.
- In an open, curvature-dominated universe the asymptotic solution is $L=At(�ln t)^{1/2}$ and $v_�infty=B(�ln t)^{-1/2}$, so the network is not scale-invariant and retains a record of when curvature domination began.
- The global-string simulation densities $�zeta_{�rm rad}=0.9�pm0.1$ and $�zeta_{�rm mat}=0.5�pm0.1$ are consistent with the extended model for $�Sigma_{�rm ax-sim}�approx3$, but the same formula predicts much weaker backreaction for cosmological GUT-scale global strings.
Reading between the lines
- If the one-parameter claim holds, a systematic drift in the fitted $�tilde c$ across radiation, matter, and transition simulations would be a clean diagnostic that the model is missing small-scale physics; conversely, a constant $�tilde c$ would support the idea that $k(v)$ absorbs the relevant small-scale effects.
- The same $v^6$ power appears in the $k$ ansatz and in the backreaction term; a wiggly-string derivation could test whether both are symptoms of one underlying small-scale structure parameter, which the paper explicitly leaves open.
- For CMB and structure-formation work, the non-scaling interval around equality suggests that bolting a scaling network onto a cosmological perturbation code is insufficient; one should integrate the VOS equations through the transition.
- The large-$�Sigma$ regime seen in small global-string simulations could serve as a calibration target for simulation systematics, but extrapolating it to $�ln(t/�delta)�sim100$ should be treated as a separate cosmological calculation.
Original abstract
We provide a general overview of the velocity-dependent one-scale model for cosmic string evolution and discuss two further extensions to it. We introduce and justify a new ansatz for the momentum parameter $k$, and also incorporate the effect of radiation backreaction. We thus discuss the evolution of the basic large-scale features of cosmic string networks in all relevant cosmological scenarios, concentrating in particular on the `scaling' solutions relevant for each case. In a companion paper, we show, by comparing with numerical simulations, that this model provides an accurate description of the large-scale features of cosmic string networks.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
We provide a general overview of the velocity-dependent one-scale model for cosmic string evolution and discuss two further extensions to it. We introduce and justify a new ansatz for the momentum parameter $k$, and also incorporate the effect of radiation backreaction. We thus discuss the evolution of the basic large-scale features of cosmic string networks in all relevant cosmological scenarios, concentrating in particular on the `scaling' solutions relevant for each case. In a companion paper, we show, by comparing with numerical simulations, that this model provides an accurate description of the large-scale features of cosmic string networks.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We provide a general overview of the velocity-dependent one-scale model for cosmic string evolution and discuss two further extensions to it. | contribution 0.77 | 0.80 | 0.08 | asserted 0.92 |
| s1 | We introduce and justify a new ansatz for the momentum parameter $k$, and also incorporate the effect of radiation backreaction. | contribution 0.95 | 0.95 | 0.09 | asserted 0.99 |
| s2 | We thus discuss the evolution of the basic large-scale features of cosmic string networks in all relevant cosmological scenarios, concentrating in particular on the `scaling' solutions relevant for each case. | contribution 0.91 | 0.80 | 0.16 | asserted 0.75 |
| s3 | In a companion paper, we show, by comparing with numerical simulations, that this model provides an accurate description of the large-scale features of cosmic string networks. | future work 0.38 | 0.73 | 0.24 | asserted 1.00 |
What was examined, and what was not
- arXiv listing abstract v1
- full text
- figures and tables
- references and citing sentences
- relations to other papers
- P abstract
- S sections
- T body sentences
- C citations
- R cross-paper relations
Figures
Figures reproduced from arXiv:hep-ph/0003298 by the authors.
References
How later papers used it
146 later papers cite it
1 paper by the same authors is listed below: 1 used its method or tool.
Uses its method or tool 1 of 47 papers with this label · 1 by the same authors
By the same authors
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Used the momentum parameter given by this paper in the system of equations it numerically integrated.
Cosmic strings and other topological defects in nonscaling regimes (2017) (same authors) · 0.85 · paraphrased: the licence does not allow quoting
How the literature uses it
137 arXiv papers cite this in 297 sentences
Papers citing it · 174 sentences without a confident label
Contests it 1 paper
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Our larger simulations do not appear to follow a spiral approach close to the fixed point as predicted by the two-parameter VOS model of [ref] , and our new value for the fixed point velocity is about $5%$ lower than the model predicts, using 4k simulations [ref] .
Scaling density of axion strings in terasite simulations · Discussion and conclusions · contest 0.74
Builds on it 6 papers
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We derived basic equations for the evolution of string segments in cosmological backgrounds by extending the velocity-dependent one-scale model with the intercommuting probability $P≠1$ [ref] .
Skewness in CMB temperature fluctuations from curved cosmic (super-)strings · Introduction · 0.92
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To this aim, we extended the Velocity One Scale (VOS) model of [ref] to describe a string network in the time-dependent case.
Cosmic (super)strings with a time-varying tension · Outlook · 1.00
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This work directly builds on previous extensions of the VOS model [ref] for describing superstring networks, which can be found in [ref] .
Dynamics of junctions and the multi-tension velocity-dependent one-scale model · Introduction · 0.90
Uses its method or tool 47 papers
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We calculated these templates numerically by solving the string-network evolution via the velocity-dependent one-scale model [ref] , shutting off the loop production after $H = m_a$, and calculating the SGWB following Ref. [ref] .
Constraining Postinflationary Axions with Pulsar Timing Arrays · Case i) $N_DW = 1$ · 1.00
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All GWB spectra in this work are calculated numerically by following [ref] (see also [ref] ) where $n_loop$ relies on the velocity-dependent one-scale (VOS) model [ref] .
Ultrahigh frequency primordial gravitational waves beyond the kHz: The case of cosmic strings · General properties of GWB from cosmic strings · 1.00
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In order to obtain the macroscopic variables for the VOS network evolution model, one needs to integrate over the spacelike variable $σ$ along all the strings in the network [ref] .
Generalised velocity-dependent one-scale model for current-carrying strings · Key Modelling Assumptions · 0.85
Uses its data or values 23 papers
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The last term accounts for energy loss into loops with $c̃$ the efficiency of chopping loops from the network, and found numerically to be $c̃ ≃0.23$ [ref] .
Gravitational waves from cosmic superstrings and gauge strings · Dynamics of long strings and loops · 1.00
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Nambu-Goto simulations are well described by $=0.23$ and a momentum parameter of the form [ref] [equation] see Ref. [ref] for the latest calibration of these parameters from the simulation of Abelian-Higgs cosmic strings.
CMB anisotropies generated by cosmic string loops · Cosmic string network evolution and loop production · 0.91
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We fix $c̅ = 0.23$ based on numerical simulations [ref] , and we use the ansatz of Ref. [ref] for the function $k()$: [equation] In terms of $ξ$ and $$, the energy density $ρ_L$ of the long string network is ρ_L = μ/(ξ t)^2 , while the rate of energy loss needed to maintain scaling is dρ_L/dt = c̅ ρ_L/(ξ t) .
Probing the pre-BBN universe with gravitational waves from cosmic strings · Cosmic string scaling and loop production · 0.89
Compares with it 3 papers
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We wish to compare the standard VOS model [ref] and the model with distinguished $v_(2)$, $v_(4)$ and $v_(6)$.
Generalised velocity-dependent one-scale model for current-carrying strings · $⟨Ẋ^4⟩$ and $⟨Ẋ^2⟩^2$ differences for standard VOS model · 0.99
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The bounds derived for the root-mean squared string velocity can be compared to theoretical expectations from recent high-resolution simulations of Nambu–Goto and Abelian–Higgs string networks, which predict velocities in the range $v_s ∼0.3$–$0.6$ during both the radiation- and matter-dominated eras [ref] .
Cosmic Strings as Dynamical Dark Energy: Novel Constraints · Constraints on Model 2: Positive energy, velocity-dependent string network. · 0.98
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If one assumes a curvature parameter $k_m$ of order unity as in the case of Goto-Nambu strings [ref] , our estimated velocities are comparable to (though possibly somewhat lower than) the ones typically encountered in other field theory defect simulations [ref] .
Evolution of Semilocal String Networks: I. Large-scale Properties · Simulation results and comparison to analytic models · 0.90
Cites it as background 26 papers
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The Velocity-dependent One-Scale (VOS) model [ref] comprises two coupled differential equations, describing how two network averaged quantities—the mean correlation length or characteristic length scale and the root mean squared velocity—evolve over cosmic time.
High resolution calibration of the cosmic strings velocity dependent one-scale model · Extended Semi-analytical modelling · 0.98
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The canonical one is the Velocity-dependent One-Scale (VOS) model, first introduced for cosmic strings [ref] and then subsequently developed for several other types of defects—for a recent overview, see [ref] .
Extending and Calibrating the Velocity dependent One-Scale model for Cosmic Strings with One Thousand Field Theory Simulations · Introduction · 0.87
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The standard analytic description of late-time coarsening is the velocity-dependent one-scale (VOS) model of Martins and Shellard [ref] .
The friction-era VOS amplitude of a $\mathbb{Z}_2$ string network from nematic disclination data · The VOS model and its calibration · 0.81
Discussion
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