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Semiclassical Smatrix for black holes
http://cds.cern.ch/record/2004546
We propose a semiclassical method to calculate Smatrix elements for twostage gravitational transitions involving matter collapse into a black hole and evaporation of the latter. The method consistently incorporates backreaction of the collapsing and emitted quanta on the metric. We illustrate the method in several toy models describing spherical selfgravitating shells in asymptotically flat and AdS spacetimes. We find that electrically neutral shells reflect via the above collapseevaporation process with probability exp(B), where B is the BekensteinHawking entropy of the intermediate black hole. This is consistent with interpretation of exp(B) as the number of black hole states. The same expression for the probability is obtained in the case of charged shells if one takes into account instability of the Cauchy horizon of the intermediate ReissnerNordstrom black hole. Our semiclassical method opens a new systematic approach to the information paradox.
Bezrukov, Fedor
Levkov, Dmitry
Sibiryakov, Sergey
Fri, 27 Mar 2015 06:41:15 GMT
24 Mar 2015
arXiv:1503.07181
http://cds.cern.ch/record/2004546

CrossOrder Integral Relations from Maximal Cuts
http://cds.cern.ch/record/2003992
We study the ABDK relation using maximal cuts of one and twoloop integrals with up to five external legs. We show how to find a special combination of integrals that allows the relation to exist, and how to reconstruct the terms with oneloop integrals squared. The reconstruction relies on the observation that integrals across different loop orders can have support on the same generalized unitarity cuts and can share global poles. We discuss the appearance of nonhomologous integration contours in multivariate residues. Their origin can be understood in simple terms, and their existence enables us to distinguish contributions from different integrals. Our analysis suggests that maximal and nearmaximal cuts can be used to infer the existence of integral identities more generally.
Johansson, Henrik
Kosower, David A
Larsen, Kasper J
Sogaard, Mads
Wed, 25 Mar 2015 17:35:58 GMT
23 Mar 2015
arXiv:1503.06711
http://cds.cern.ch/record/2003992

Gluino Coannihilation Revisited
http://cds.cern.ch/record/2003926
Some variants of the MSSM feature a strip in parameter space where the lightest neutralino is identified as the lightest supersymmetric particle (LSP), the gluino is the nexttolightest supersymmetric particle (NLSP) and is nearly degenerate with the LSP, and the relic cold dark matter density is brought into the range allowed by astrophysics and cosmology by coannihilation with the gluino NLSP. We calculate the relic density along this gluino coannihilation strip in the MSSM, including the effects of gluinogluino bound states and initialstate Sommerfeld enhancement, and taking into account the decoupling of the gluino and LSP densities that occurs for large values of the squark mass. We find that boundstate effects can increase the maximum LSP mass for which the relic cold dark matter density lies within the range favoured by astrophysics and cosmology by as much as ~ 50% if the squark to gluino mass ratio is 1.1, and that the LSP may weigh up to ~ 8 TeV for a wide range of the squark to gluino mass ratio \lesssim 100.
Ellis, John
Luo, Feng
Olive, Keith A
Wed, 25 Mar 2015 17:31:20 GMT
24 Mar 2015
arXiv:1503.07142
http://cds.cern.ch/record/2003926

Matching NLO QCD with parton shower in Monte Carlo scheme  the KrkNLO method
http://cds.cern.ch/record/2003785
A new method of including the complete NLO QCD corrections to hard processes in the LO partonshower Monte Carlo (PSMC) is presented. This method, called KrkNLO, requires the use of parton distribution functions in a dedicated Monte Carlo factorization scheme, which is also discussed in this paper. In the future, it may simplify introduction of the NNLO corrections to hard processes and the NLO corrections to PSMC. Details of the method and numerical examples of its practical implementation, as well as comparisons with other calculations, such as MCFM, MC@NLO, POWHEG, for single $Z/\gamma^*$boson production at the LHC, are presented.
Jadach, S
Placzek, W
Sapeta, S
Siodmok, A
Skrzypek, M
Wed, 25 Mar 2015 17:10:39 GMT
23 Mar 2015
arXiv:1503.06849
http://cds.cern.ch/record/2003785

Higgs boson gluonfusion production in N3LO QCD
http://cds.cern.ch/record/2003776
We present the crosssection for the production of a Higgs boson at hadroncolliders at nextto nexttonexttoleading order (N3LO) in perturbative QCD. The calculation is based on a method to perform a series expansion of the partonic crosssection around the threshold limit to an arbitrary order. We perform this expansion to sufficiently high order to obtain the value of the hadronic cross at N3LO in the large topmass limit. For renormalisation and factorisation scales equal to half the Higgs mass, the N3LO corrections are of the order of +2.2%. The total scale variation at N3LO is 3%, reducing the uncertainty due to missing higher order QCD corrections by a factor of three.
Anastasiou, Charalampos
Duhr, Claude
Dulat, Falko
Herzog, Franz
Mistlberger, Bernhard
Wed, 25 Mar 2015 17:10:36 GMT
20 Mar 2015
arXiv:1503.06056
http://cds.cern.ch/record/2003776

Constraining Dark Sectors with Monojets and Dijets
http://cds.cern.ch/record/2003772
We consider dark sector particles (DSPs) that obtain sizeable interactions with Standard Model fermions from a new mediator. While these particles can avoid observation in direct detection experiments, they are strongly constrained by LHC measurements. We demonstrate that there is an important complementarity between searches for DSP production and searches for the mediator itself, in particular bounds on (broad) dijet resonances. This observation is crucial not only in the case where the DSP is all of the dark matter but whenever  precisely due to its sizeable interactions with the visible sector  the DSP annihilates away so efficiently that it only forms a dark matter subcomponent. To highlight the different roles of DSP direct detection and LHC monojet and dijet searches, as well as perturbativity constraints, we first analyse the exemplary case of an axialvector mediator and then generalise our results. We find important implications for the interpretation of LHC dark matter searches in terms of simplified models.
Chala, Mikael
Kahlhoefer, Felix
McCullough, Matthew
Nardini, Germano
SchmidtHoberg, Kai
Wed, 25 Mar 2015 17:10:31 GMT
19 Mar 2015
arXiv:1503.05916
http://cds.cern.ch/record/2003772

Anomalous triple gauge couplings from $B$meson and kaon observables
http://cds.cern.ch/record/2003752
We consider the three CPconserving dimension6 operators that encode the leading newphysics effects in the triple gauge couplings. The contributions to the standardmodel electromagnetic dipole and semileptonic vector and axialvector interactions that arise from the insertions of these operators are calculated. We show that radiative and rare $B$meson decays provide, under certain assumptions, constraints on two out of the three anomalous couplings that are competitive with the restrictions obtained from LEP II, Tevatron and LHC data. The constraints arising from the $Z \to b \bar b$ electroweak pseudo observables, $K \to \pi \nu \bar \nu$ and $\epsilon^\prime/\epsilon$ are also studied.
Bobeth, Christoph
Haisch, Ulrich
Wed, 25 Mar 2015 17:10:24 GMT
16 Mar 2015
arXiv:1503.04829
http://cds.cern.ch/record/2003752

Doubly SelfDual Actions in Various Dimensions
http://cds.cern.ch/record/2003678
The selfduality of the N=1 supersymmetric BornInfeld action implies a double selfduality of the tensor multiplet squareroot action when the scalar and the antisymmetric tensor are interchanged via Poincare' duality. We show how this phenomenon extends to D spacetime dimensions for nonlinear actions involving pairs of forms of rank p and Dp2. As a byproduct, we construct a new twofield generalization of the BornInfeld action whose equations of motion are invariant under a U(1) duality. In these systems, the introduction of GreenSchwarz terms results in explicit nonlinear masslike terms for dual massive pairs.
Ferrara, S
Sagnotti, A
Yeranyan, A
Wed, 25 Mar 2015 17:07:10 GMT
16 Mar 2015
arXiv:1503.04731
http://cds.cern.ch/record/2003678

A StringInspired Model for the Low$\ell$ CMB
http://cds.cern.ch/record/2003308
We present a detailed exploration of a family of low$\ell$ angular power spectra inspired by "Brane Supersymmetry Breaking". This mechanism splits Bose and Fermi excitations in String Theory and leaves behind \emph{an exponential potential that is just too steep for the inflaton to emerge from the initial singularity while descending it}. As a result, the scalar generically bounces against the exponential wall, which typically introduces \emph{an infrared depression and a preinflationary peak} in the power spectrum of scalar perturbations. We elaborate on a possible link between this phenomenon and the low$\ell$ CMB. For the first 32 multipoles, combining the hard exponential with a milder one leading to $n_s\simeq 0.96$ and with a small gaussian bump we have attained a reduction of $\chi^{\,2}$ to about 46\% of the standard $\Lambda$CDM setting, with both WMAP9 and PLANCK 2013 data. This result corresponds to a $\chi^{\,2}/DOF$ of about 0.45, to be compared with a $\Lambda$CDM value of about 0.85. The preferred choices combine naturally quadrupole depression, a first peak around $\ell=5$ and a wide minimum around $\ell=20$. We have also gathered some evidence that similar spectra emerge if the hard exponential is combined with more realistic models of inflation.
Kitazawa, N
Sagnotti, A
Wed, 25 Mar 2015 17:01:27 GMT
15 Mar 2015
arXiv:1503.04483
http://cds.cern.ch/record/2003308

Improved TMD factorization for forward dijet production in dilutedense hadronic collisions
http://cds.cern.ch/record/2001367
We study forward dijet production in dilutedense hadronic collisions. By considering the appropriate limits, we show that both the transversemomentumdependent (TMD) and the highenergy factorization formulas can be derived from the Color Glass Condensate framework. Respectively, this happens when the transverse momentum imbalance of the dijet system, $k_t$, is of the order of either the saturation scale, or the hard jet momenta, the former being always much smaller than the latter. We propose a new formula for forward dijets that encompasses both situations and is therefore applicable regardless of the magnitude of $k_t$. That involves generalizing the TMD factorization formula for dijet production to the case where the incoming small$x$ gluon is offshell. The derivation is performed in two independent ways, using either Feynman diagram techniques, or colorordered amplitudes.
Kotko, P
Kutak, K
Marquet, C
Petreska, E
Sapeta, S
van Hameren, A
Fri, 13 Mar 2015 06:53:39 GMT
11 Mar 2015
arXiv:1503.03421
http://cds.cern.ch/record/2001367

Mass Measurement Using Energy Spectra in Threebody Decays
http://cds.cern.ch/record/2001343
In previous works we have demonstrated how the energy distribution of massless decay products in two body decays can be used to measure the mass of decaying particles. In this work we show how such results can be generalized to the case of multibody decays. The key ideas that allow us to deal with multibody final states are an extension of our previous results to the case of massive decay products and the factorization of the multibody phase space. The mass measurement strategy that we propose is distinct from alternative methods because it does not require an accurate reconstruction of the entire event, as it does not involve, for instance, the missing transverse momentum, but rather requires measuring only the visible decay products of the decay of interest. To demonstrate the general strategy, we study a supersymmetric model wherein pairproduced gluinos each decay to a stable neutralino and a bottom quarkantiquark pair via an offshell bottom squark. The combinatorial background stemming from the indistinguishable visible final states on both decay sides can be treated by an "event mixing" technique, the performance of which is discussed in detail. Taking into account dominant backgrounds, we are able to show that the mass of the gluino and, in favorable cases, that of the neutralino can be determined by this mass measurement strategy.
Agashe, Kaustubh
Franceschini, Roberto
Kim, Doojin
Wardlow, Kyle
Fri, 13 Mar 2015 06:51:23 GMT
12 Mar 2015
arXiv:1503.03836
http://cds.cern.ch/record/2001343

Addressing the LHC flavour anomalies with horizontal gauge symmetries
http://cds.cern.ch/record/2001333
We study the impact of an additional $U(1)'$ gauge symmetry with flavourdependent charges for quarks and leptons on the LHC flavour anomalies observed in $B \to K^* \mu^+\mu^$, $R(K) = B \to K \mu^+\mu^/B \to K e^+e^$ and $h \to \mu\tau$. In its minimal version with two scalar doublets the resulting model naturally explains the deviations from the Standard Model observed in $B \to K^* \mu^+\mu^$ and $R(K)$. The CMS access in $h \to \mu\tau$ can be explained by introducing a third scalar doublet, which gives rise to a prediction for $\tau \to 3\mu$. We investigate constraints from flavour observables and direct LHC searches for $pp \to Z' \to \mu^+\mu^$. Our model successfully generates the measured fermionmixing matrices and does not require vectorlike fermions, unlike previous attempts to explain these anomalies.
Crivellin, Andreas
D'Ambrosio, Giancarlo
Heeck, Julian
Fri, 13 Mar 2015 06:51:08 GMT
11 Mar 2015
arXiv:1503.03477
http://cds.cern.ch/record/2001333

Light stops, blind spots, and isospin violation in the MSSM
http://cds.cern.ch/record/2001258
In the framework of the MSSM, we examine several simplified models where only a few superpartners are light. This allows us to study WIMPnucleus scattering in terms of a handful of MSSM parameters and thereby scrutinize their impact on dark matter directdetection experiments. Focusing on spinindependent WIMPnucleon scattering, we derive simplified, analytic expressions for the Wilson coefficients associated with Higgs and squark exchange. We utilize these results to study the complementarity of constraints due to directdetection, flavor, and collider experiments. We also identify parameter configurations that produce (almost) vanishing cross sections. In the proximity of these socalled blind spots, the amount of isospin violation is found to be much larger than typically expected in the MSSM. This feature is a generic property of parameter regions where cross sections are suppressed, and highlights the importance of a careful analysis of the nucleon couplings and the associated hadronic uncertainties. This becomes especially relevant once the increased sensitivity of future directdetection experiments corners the MSSM into these regions of parameter space.
Crivellin, Andreas
Hoferichter, Martin
Procura, Massimiliano
Tunstall, Lewis C
Fri, 13 Mar 2015 06:48:47 GMT
11 Mar 2015
arXiv:1503.03478
http://cds.cern.ch/record/2001258

On stability of electroweak vacuum during inflation
http://cds.cern.ch/record/2000570
We study ColemanDe Luccia tunneling of the Standard Model Higgs field during inflation in the case when the electroweak vacuum is metastable. We verify that the tunneling rate is exponentially suppressed. The main contribution to the suppression is the same as in flat spacetime. We analytically estimate the corrections due to the expansion of the universe and an effective mass term in the Higgs potential that can be present at inflation.
Shkerin, Andrey
Sibiryakov, Sergey
Wed, 11 Mar 2015 06:48:04 GMT
06 Mar 2015
arXiv:1503.02586
http://cds.cern.ch/record/2000570

Signatures of Majorana dark matter with tchannel mediators
http://cds.cern.ch/record/1999386
Three main strategies are being pursued to search for nongravitational dark matter signals: direct detection, indirect detection and collider searches. Interestingly, experiments have reached sensitivities in these three search strategies which may allow detection in the near future. In order to take full benefit of the wealth of experimental data, and in order to confirm a possible dark matter signal, it is necessary to specify the nature of the dark matter particle and of the mediator to the Standard Model. In this paper, we focus on a simplified model where the dark matter particle is a Majorana fermion that couples to a light Standard Model fermion via a Yukawa coupling with a scalar mediator. We review the observational signatures of this model and we discuss the complementarity among the various search strategies, with emphasis in the well motivated scenario where the dark matter particles are produced in the early Universe via thermal freezeout.
Garny, Mathias
Ibarra, Alejandro
Vogl, Stefan
Sat, 07 Mar 2015 06:51:30 GMT
04 Mar 2015
arXiv:1503.01500
http://cds.cern.ch/record/1999386

Froissart Bound on Inelastic Cross Section Without Unknown Constants
http://cds.cern.ch/record/1997117
Assuming that axiomatic local field theory results hold for hadron scattering, Andr\'e Martin and S. M. Roy recently obtained absolute bounds on the Dwave below threshold for pionpion scattering and thereby determined the scale of the logarithm in the Froissart bound on total cross sections in terms of pion mass only. Previously, Martin proved a rigorous upper bound on the inelastic crosssection $\sigma_{inel}$ which is onefourth of the corresponding upper bound on $\sigma_{tot}$, and Wu, Martin,Roy and Singh improved the bound by adding the constraint of a given $\sigma_{tot}$. Here we use unitarity and analyticity to determine, without any high energy approximation, upper bounds on energy averaged inelastic cross sections in terms of low energy data in the crossed channel. These are Froissarttype bounds without any unknown coefficient or unknown scale factors and can be tested experimentally. Alternatively, their asymptotic forms,together with the MartinRoy absolute bounds on pionpion Dwaves below threshold, yield absolute bounds on energyaveraged inelastic cross sections. E.g. for $\pi^0 \pi^0$ scattering, defining $\sigma_{inel}=\sigma_{tot} \big (\sigma^{\pi^0 \pi^0 \rightarrow \pi^0 \pi^0} + \sigma^{\pi^0 \pi^0 \rightarrow \pi^+ \pi^} \big )$,we show that for c.m. energy $\sqrt{s}\rightarrow \infty $, $\bar{\sigma}_{inel }(s,\infty)\equiv s\int_{s} ^{\infty } ds'\sigma_{inel }(s')/s'^2 \leq (\pi /4) (m_{\pi })^{2} [\ln (s/s_1)+(1/2)\ln \ln (s/s_1) +1]^2$ where $1/s_1= 34\pi \sqrt{2\pi }\>m_{\pi }^{2} $ . This bound is asymptotically onefourth of the corresponding MartinRoy bound on the total cross section, and the scale factor $s_1$ is onefourth of the scale factor in the total cross section bound. The average over the interval (s,2s) of the inelastic $\pi^0 \pi^0 $cross section has a bound of the same form with $1/s_1$ replaced by $1/s_2=2/s_1 $.
Martin, AndrĂ©
Roy, S M
Thu, 05 Mar 2015 07:11:16 GMT
04 Mar 2015
arXiv:1503.01261
http://cds.cern.ch/record/1997117

Gaugeinvariant signatures of spontaneous gauge symmetry breaking by the Hosotani mechanism
http://cds.cern.ch/record/1996449
The Hosotani mechanism claims to achieve gaugesymmetry breaking, for instance $SU(3) \to SU(2)\times U(1)$. To verify this claim, we propose to monitor the stability of a topological defect stable under a gauge subgroup but not under the whole gauge group, like a $U(1)$ flux state or monopole in the case above. We use gauge invariant operators to probe the presence of the topological defect to avoid any ambiguity introduced by gauge fixing. Our method also applies to an ordinary gaugeHiggs system.
Akerlund, Oscar
de Forcrand, Philippe
Wed, 04 Mar 2015 06:42:56 GMT
02 Mar 2015
arXiv:1503.00429
http://cds.cern.ch/record/1996449

On jet substructure methods for signal jets
http://cds.cern.ch/record/1996443
We carry out simple analytical calculations and Monte Carlo studies to better understand the impact of QCD radiation on some wellknown jet substructure methods for jets arising from the decay of boosted Higgs bosons. Understanding differences between taggers for these signal jets assumes particular significance in situations where they perform similarly on QCD background jets. As an explicit example of this we compare the Ysplitter method to the more recently proposed Ypruning technique. We demonstrate how the insight we gain can be used to significantly improve the performance of Ysplitter by combining it with trimming and show that this combination outperforms the other taggers studied here, at high $p_T$. We also make analytical estimates for optimal parameter values, for a range of methods and compare to results from Monte Carlo studies.
Dasgupta, Mrinal
Powling, Alexander
Siodmok, Andrzej
Wed, 04 Mar 2015 06:40:25 GMT
03 Mar 2015
arXiv:1503.01088
http://cds.cern.ch/record/1996443

Universality of radiative corrections to gauge couplings for strings with spontaneously broken supersymmetry
http://cds.cern.ch/record/1995142
I review recent work on computing radiative corrections to nonabelian gauge couplings in fourdimensional heterotic vacua with spontaneously broken supersymmetry. The prototype models can be considered as K3 surfaces with additional ScherkSchwarz fluxes inducing the spontaneous $\mathcal{N}=2 \to \mathcal{N}=0$ breaking. Remarkably, although the gauge thresholds are no longer BPS protected and receive contributions also from the excitations of the RNS sector, their difference is still exactly computable and universal. Based on a talk presented at the DISCRETE 2014 conference at King's College London.
Florakis, Ioannis
Sat, 28 Feb 2015 07:51:05 GMT
26 Feb 2015
arXiv:1502.07537
http://cds.cern.ch/record/1995142

Emerging Jets
http://cds.cern.ch/record/1993313
In this work, we propose a novel search strategy for new physics at the LHC that utilizes calorimeter jets that (i) are composed dominantly of displaced tracks and (ii) have many different vertices within the jet cone. Such emerging jet signatures are smoking guns for models with a composite dark sector where a parton shower in the dark sector is followed by displaced decays of dark pions back to SM jets. No current LHC searches are sensitive to this type of phenomenology. We perform a detailed simulation for a benchmark signal with two regular and two emerging jets, and present and implement strategies to suppress QCD backgrounds by up to six orders of magnitude. At the 14 TeV LHC, this signature can be probed with mediator masses as large as 1.5 TeV for a range of dark pion lifetimes, and the reach is increased further at the highluminosity LHC. The emerging jet search is also sensitive to a broad class of longlived phenomena, and we show this for a supersymmetric model with Rparity violation. Possibilities for discovery at LHCb are also discussed.
Schwaller, Pedro
Stolarski, Daniel
Weiler, Andreas
Fri, 20 Feb 2015 08:33:38 GMT
18 Feb 2015
arXiv:1502.05409
http://cds.cern.ch/record/1993313

Towards the physical point hadronic vacuum polarisation from Moebius DWF
http://cds.cern.ch/record/1992983
We present steps towards the computation of the leadingorder hadronic contribution to the muon anomalous magnetic moment on RBC/UKQCD physical point DWF ensembles. We discuss several methods for controlling and reducing uncertainties associated to the determination of the HVP form factor.
Marinkovic, Marina
Boyle, Peter
Del Debbio, Luigi
Juettner, Andreas
Maltman, Kim
Portelli, Antonin
Thu, 19 Feb 2015 06:53:17 GMT
18 Feb 2015
arXiv:1502.05308
http://cds.cern.ch/record/1992983

Fundamental Composite Electroweak Dynamics: Status at the LHC
http://cds.cern.ch/record/1992768
We determine the current status of the fundamental composite electroweak dynamics paradigm after the discovery of the Higgs boson at the Large Hadron Collider experiments. Our analysis serves as universal and minimal template for a wide class of models with the two limits in parameter space being composite Goldstone Higgs models and Technicolor. This is possible because of the existence of a unified description, both at the effective and fundamental Lagrangian levels, of models of composite Higgs dynamics where the Higgs boson itself can emerge, depending on the way the electroweak symmetry is embedded, either as a pseudoGoldstone boson or as a massive excitation of the condensate. We constrain the available parameter space at the effective Lagrangian level. We show that a wide class of models of fundamental composite electroweak dynamics, including Technicolor, are compatible with experiments. The results are relevant for future searches of a fundamental composite nature of the Higgs mechanism at the Large Hadron Collider.
Arbey, Alexandre
Cacciapaglia, Giacomo
Cai, Haiying
Deandrea, Aldo
Le Corre, Solene
Sannino, Francesco
Wed, 18 Feb 2015 06:43:44 GMT
16 Feb 2015
arXiv:1502.04718
http://cds.cern.ch/record/1992768

Robust collider limits on heavymediator Dark Matter
http://cds.cern.ch/record/1992767
We discuss how to consistently use Effective Field Theories (EFTs) to set universal bounds on heavymediator Dark Matter at colliders, without prejudice on the model underlying a given effective interaction. We illustrate the method for a Majorana fermion, universally coupled to the Standard Model quarks via a dimension6 axialaxial fourfermion operator. We recast the ATLAS monojet analysis and show that a considerable fraction of the parameter space, seemingly excluded by a na\"ive EFT interpretation, is actually still unexplored. Consistently set EFT limits can be reinterpreted in any specific underlying model. We provide two explicit examples for the chosen operator and compare the reach of our modelindependent method with that obtainable by dedicated analyses.
Racco, Davide
Wulzer, Andrea
Zwirner, Fabio
Wed, 18 Feb 2015 06:43:42 GMT
16 Feb 2015
arXiv:1502.04701
http://cds.cern.ch/record/1992767

Black Hole Solutions in $R^2$ Gravity
http://cds.cern.ch/record/1992512
We find static spherically symmetric solutions of scale invariant $R^2$ gravity. The latter has been shown to be equivalent to General Relativity with a positive cosmological constant and a scalar mode. Therefore, one expects that solutions of the $R^2$ theory will be identical to that of Einstein theory. Indeed, we find that the solutions of $R^2$ gravity are in onetoone correspondence with solutions of General Relativity in the case of nonvanishing Ricci scalar. However, scalarflat $R=0$ solutions are global minima of the $R^2$ action and they cannot in general be mapped to solutions of the Einstein theory. As we will discuss, the $R=0$ solutions arise in Einstein gravity as solutions in the tensionless, strong coupling limit $M_P\rightarrow 0$. As a further result, there is no corresponding Birkhoff theorem and the Schwarzschild black hole is by no means unique in this framework. In fact, $R^2$ gravity has a rich structure of vacuum static spherically symmetric solutions partially uncovered here. We also find charged static spherically symmetric backgrounds coupled to a $U(1)$ field. Finally, we provide the entropy and energy formulas for the $R^2$ theory and we find that entropy and energy vanish for scalarflat backgrounds.
Kehagias, Alex
Kounnas, Costas
Lust, Dieter
Riotto, Antonio
Tue, 17 Feb 2015 06:33:49 GMT
14 Feb 2015
arXiv:1502.04192
http://cds.cern.ch/record/1992512

$D^6 R^4$ amplitudes in various dimensions
http://cds.cern.ch/record/1989347
Fourgraviton couplings in the low energy effective action of type II string vacua compactified on tori are strongly constrained by supersymmetry and Uduality. While the $R^4$ and $D^4 R^4$ couplings are known exactly in terms of LanglandsEisenstein series of the Uduality group, the $D^6 R^4$ couplings are not nearly as well understood. Exploiting the coincidence of the Uduality group in $D=6$ with the Tduality group in $D=5$, we propose an exact formula for the $D^6 R^4$ couplings in type II string theory compactified on $T^4$, in terms of a genustwo modular integral plus a suitable Eisenstein series. The same modular integral computes the twoloop correction to $D^6 R^4$ in 5 dimensions, but here provides the nonperturbative completion of the known perturbative terms in $D=6$. This proposal hinges on a systematic reanalysis of the weak coupling and large radius of the $D^6 R^4$ in all dimensions $D\geq 3$, which fills in some gaps and resolves some inconsistencies in earlier studies.
Pioline, Boris
Fri, 13 Feb 2015 06:37:29 GMT
11 Feb 2015
arXiv:1502.03377
http://cds.cern.ch/record/1989347